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A Comparative Study of Oöcyte Development in False Ovoviviparous Cockroaches.
Psyche 69(4):165-208, 1962.
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PSYCHE
Vol. 69 DECEMBER, 1962 No. 4
A COMPARATIVE STUDY OF
OOCYTE DEVELOPMENT IN FALSE
OVOVIVIPAROUS COCKROACHES*
BY LOUIS M. ROTH AND BARBARA STAY^
Pioneering Research Laboratories
Quartermaster Research and Engineering Center Natick, Massachusetts
Recently Engeln~ann (1960) compared various internal and exter- nal factors which affect the activity of the corpora allata in Leuco- $ham maderae (Fabricius) and Diplotera punctata (Eschscholtz) . In these two species the stimuli resulting from mating, food intake, gesta- tion, and parturition differed in the degree to which they influenced production of gonadotropic hormone.
In this paper we report our experiments on control of oocyte devel- opment in several species of cockroaches that incubate their eggs internally in a brood sac or uterus. We classify these species as false ovoviviparous forms because the uterine eggs increase in water content only (Roth and Willis, I 955 ) as opposed to false viviparous species, like Diplofitera, in which the embryos take up both water and solids from the mother (Roth and Willis, 1955a). In both groups the oviposition behavior is similar. The eggs do not pass directly from the ovaries into the uterus but are first extruded to the outside of the body and then retracted into the brood sac (Roth and Willis, 1954, 1958). Cockroaches that incubate their eggs internally have two birth products, the egg and nymph (Roth and Willis, 1958). Ovulation and oviposition refer to the eggs being released from the ovaries, oriented by the ovipositor, and covered by the ootheca. After the eggs are in the uterus the females are pregnant (gestation) for a certain period of time and give birth (parturition) to nymphs, MATERIALS AND METHODS
Except for one series of experiments on Nauphoeta (see page I 74)) all insects were reared on dog chow checkers and maintained at 24' *Manuscript received by the editor August 1,1962. 'Present address: Department of Zoology, University of Pennsylvania, Philadelphia, Pennsylvania.
165
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I 66 Psyche [December
to 2s0 C. and 50 to 70% relative humidity. Engelmann (1957, 1959) showed that yolk deposition and growth of the oocytes are correlated with and dependent upon activity of the corpora allata in Leucophaea and Diploptera and we have used oocyte development as an indicator of endocrine activity. Measurements were made, with an ocular mic- rometer, of oocytes that were dissected from ovaries in Ringer's solu- tion. Our measurements of the oocytes of Leucophaea are larger than those reported by Engelmann ( 1960). This discrepancy is probably due to the fact that he measured the oocytes after fixation (Engel- mann, 195 7). We measured one large oocyte per female; in establish- ing the normal ovarian cycle or the sizes of the oocytes at a specific period a number of females were usually dissected to give some indica- tion of the extent of variation. Various operations (allatectomy, nerve cord severance, etc.) were performed on insects kept under carbon dioxide anesthesia.
The species reported on in this paper are Pycnoscelus surinamensis (Linnaeus) , Byrsotria fumigata (Gukrin) , Blaberus craniifer Bur- meister, Blaberus giganteus (Linnaeus) , Nauphoeta cinerea (Olivier ), and Leucophaea maderae. There are two strains of Pycnoscelus suri- namensis which differ physiologically. The bisexual strain cannot reproduce parthenogenetically and the parthenogenetic strain females when mated to males of the bisexual form show a reduction in fertility and the resulting offspring are all females which reproduce partheno- genetically (Roth and Willis, 1961).
Practically all of the experi-
ments on Pycnoscelus were done on the parthenogenetic strain but a few were performed o,n the bisexual form. A similar study on control of oocyte development in Diploptera and two species of BlatteZla has been reported elsewhere (Roth and Stay, 1961, 1962). RESULTS AND DISCUSSION
Oocyte development in virgin and mated females Py cnoscelus surinamensis: Biological data for the two strains are given in table I. The basal oocytes of the ovarioles of females less than a day old are large and may already contain yolk. In fact yolk may be present in the oocytes of some newly-emerged adults indicating that gonadotropic hormone had already been released in the nymphal stage.
The ovarian cycle from emergence to the formation of the second ootheca in the parthenogenetic strain is shown in figure I. During gestation the oocytes remain small and increase only slight- ly in length during the development of the eggs in the uterus. Yolk deposition occurs after parturition and the oGcytes increase rapidly in size.
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Table I - Biological Data For Two Strains of Pycnosccl~[s surinamensis BIOLOGICAL OBSERVATION
Length (mm.) of oocytes
less than 1 day after
emergence of adult
Length (mm.) of mature
oocytes at oviposition3
Length (mm.) of new
basal oocyte at
time of oviposition
'S.E.=standard error, here and in all following tables. %=number of insects, here and in all following tables. "Data from Roth and Willis (1961).
PARTHENOGENETIC STRAIN
Min.
Max. Mean å S.E.l N'
0.86
0.99 0.91 & 0.03 5
day after parturition
Age (days) at first
ovulation
Virgins
Mated
Gestation (days)3
Virgins
Mated
Number days to
ovulation following
parturition3
u
BISEXUAL STRAIN
Min. Max. Mean 31 S.E. N
0.73 0.94
0.85 k 0.02 10
2.97
3.36 3.21 k 0.04 10
0.50
0.57 0.53 k0.01 6
2.69 3.36 2.99 iz 0.04
l5 b o
Ìö-+
0.50 0.74 0.60 5 0.02 16
a
ft^
Length (mm.) of basal 0.79 0.74k 0.01 10 oocvtes less than 1
10 20 12.8 2 0.1 244
- -
- -
-
5 3 5 8 55.450.3 20
- - - - -
14 17 15.5 k 0.3 11
0.69 0.79 0.745 0.01
F
5 - I
1
0
^t-
8 25 13.6å 0.2 138 2
9 22 11.920.1
-
59 g
a-
"a t->
- - - - -
50 5 6 52.8 * 0.2 37
10 16 14.2 k 0.7 8
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I 68 Psy c lz e [December
In the parthenogenetic strain the first ovulation occurs when the female is about 13 days old whereas the second ovulation takes place about 16 days after birth of young. This 3 day difference is explained by the difference in size of the oocytes in the newly-emerged female and in the female at parturition; the oocytes are smaller after the female gives birth and it takes about 3 days to attain the same degree of development as they are at adult emergence. In Diploptera the reverse is true and the second preovulation period is 3 days shorter than the first although, as in Pycnoscelus the growth rate of the oocytes is about the same during the first and second preovulation periods. In Diplofitera the oocytes at parturition are about the size of those of a 3-day-old mated female which explains the shorter period required for ovulation after parturition (Engelmann, 1959). Pycnoscelus surinomensis
3 fi!- OVIPOSITION
OVIPOSITION
GESTATION ->
Fig. 1. Ovarian cycle of Pycnoscelus surinamensis (parthenogenetic strain). Each point on the curve for oocyte development from 0 to 13 days is the mean of 6 to 13 measurements (NÌÔ134) Each point for the gestation period from 13 to 68 days represents individual measurements (NÌÔ99 when 2 or more points were similar for a particular age only one is indicated). The part of the curve representing the growth of the oocytes after parturition (birth) is based on 1 to 3 individuals (NÌÔ24 for each point. Vertical bars -
-standard errors of mean values.
In the parthenogenetic strain of Pycnoscelus it is obvious that mat- ing is unnecessary for development of the oocytes. The initial develop- ment of the oocytes in the bisexual strain is similar to that found in the parthenogenetic form but differs in that mating slightly stimulates the growth rate and also is necessary for normal retraction of the ootheca into the uterus. Mating a parthenogenetic strain female with a male
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19621 Roth and Stay - Cockroaches 169
of the bisexual strain has no stimulating effect on growth of the oocytes as indicated by age of the female at ovulation (Roth and Willis, I 961 ) .
Six parthenogenetic strain females, allatecto~nized when I - 2 days old, did not oviposit within a month after the operations. Five of these females had 2 pairs of corpora allata implanted at 29 to 30 days aftei- allatectomy. Four produced oothecae in less than 35 days and one died after 44 days. At I I I days after allatectomy one female that still had not ovulated received corpora allata implants and oviposited in less than 21 days. This strain normally oviposits about 13 days after emergence (table I). The delay in oviposition after implanting cor- pora allata may have been due to the presence of degenerating oocytes in the ovaries since the oocytes already have yolk one to two days after emergence (the age at which allatectomy was performed). In Leuco- phaea, oocytes in resorption inhibit the corpora allata (Engelmann, 1957).
Table 2 - Effect of mating on oocyte development and oviposition in Byrsotria fumigata
OBSERVATION
Total number observed
Number oviposited
Ootheca retracted normally
Ootheca incompletely retracted
Ootheca dropped
Number failed to oviposit
Oocytes large, well developed
or matured but degenerating
and being resorbed
Oocytes small, abnormal in
shape, being resorbed
Oocytes small, normal in
appearance but only
slightly or not at all developed
MATED
VIRGIN
'Three of the 4 females had sperm in their spermathecae; one lacked sperm.
*These females were 35 to 60 days old when dissected. had sperm in their spermathecae.
twenty-one of these females were 32 to 60 days old. The other 14 were 11 to 24 days of age but since their oocytes were small and abnormal they would not have oviposited.
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Psyche
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AGE OF FEMALE (DAYS)
&sotria fumigate!
o = Oocytes,virgin females
= Oocytes, mated females
'
8 = Degenerating oocytes, virgin females Fig. 2. Growth of oocytes in virgin and mated females of Byrsotria ft gata. Each point represents one female.
Females were mated when 1 tc
days old.
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19621 Roth and Stay - Cockroaches I7 *
Byrsotria fumigata: The effects of mating on oocyte development and oviposition in Byrsotria are shown in table 2 and figure 2. About 50 percent of the virgin females failed to oviposit but of these I 11 females 61 % had large well-developed oocytes that were degenerating or were being resorbed (fig. 14E). It is evident from figure 2 that after the thirty-fifth day of age the oocytes of many virgins degenerate although most of them may reach a length of 5 mm. or more. About 16% of the virgins and about 10% of the mated females had small abnormally-shaped oocytes that were being resorbed. It is unlikely that lack of hormone is responsible for this type of abnormality since Barth (personal communication) has dissected pheromone-producing Byrsotria females which had small degenerating oocytes but accessory glands filled with secretion.
In those females that mate, copulation has little, if any, effect on the growth rate of the oocytes (fig. 2). Mated females oviposited at 26 to 41 days of age (Z=32.4å±0. days; N=53) ; virgin females oviposited 26 to 44 days after emergence (?=34.3å±0. days; N= 121). That there is little effect on the rate of growth resulting from mating is further borne out by the fact that the females oviposit at about the same age regardless of their age when mated. In our series the females were with males continuously until they mated; copula- tion occurred from 4 to 25 days after female emergence. The oocytes may vary considerably in size in females between these age limits (fig. 2). A female with large oocytes mated when 25 days old may ovulate 10 days later whereas one with small oocytes mated at 4 days of age may take 30 days to ovulate (fig. 3). This is quite different from the effect of mating in Leucophaea (Engelmann, 1960) where the average interval between mating and oviposition is about the same regardless of the age of the female when mated (fig. 3) because the females tend to mate more readily when their oocytes reach a certain size (see below) . Barth ( 1961 ) found that Byrsotria females begin to produce sex pheromone 10 to 30 days after the imaginal molt; however, recently (1962) he has found that some females may mate as early as 4 days after adult emergence. It seems that in Byrsotria mating (perhaps the presence of sperm in the spermathecae) serves
as a stimulus to oviposition.
This is
indicated by the fact that the oocytes in many virgin females apparent- ly mature yet ovulation does not occur. The oocytes in virgin females at ovulation vary in length from 5.90 to 7.60 mm. (2=6.79å±0.0 ; N=7). Although the mean ages at ovulation of mated and virgin females are very similar a breakdown of the data (fig. 4) shows that
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Psyche [December
Fig. 3.. Relationship between age at mating and ovulation (as indicated by oviposition) in 4 species of cockroaches. Each point represents one female. (N = 3 56 for Leucophaea) .
38% of the virgins oviposited after the thirty-fifth day as compared to I 3% of mated females.
Fifteen virgin females allatectomized when I to 2 days old did not produce oothecae within more than 50 days. At 52 to 210 days after allatectomy, corpora allata were implanted; 9 females ovulated in less than 82 days and one oviposited in 128 days; 3 died without oviposit- ng and two dissected after 150 days had small undeveloped oocytes. One allatectomized female that oviposited after receiving corpora allata implants had well developed oocytes although the ootheca was in the uterus (fig. 14D). Of 25 sham operated females 16 oviposited in less than 56 days. We don't know how to account for the delay in ovulation after implantation of corpora allata into allatectomized females. Four pregnant females (i.e. with an ootheca in the brood sac) had corpora allata implanted and were dissected at 35 to 41 days of pregnancy. Their oocytes measured 4.90 to 6.81 mm. in length
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19621 Roth and Stay -- Cockroaches I73
indicating renewed growth of the ovarian eggs as a result of the implants.
Nauphoeta cinerea: The oocytes of virgins develop but unless mating occurs the oocytes in many females may degenerate before they reach ovulation size (fig. 5). Virgin females that ovulate do so in 31 to 47 days (x=35.8zk1.2 days; N=17). Mating results in stimu- Blaberus craniifer
AGE OF FEMALE (DAYS)
Fig. 4. Effect of mating on oviposition. Solid circlesÌÔvirgi females. Open circlesÌÔmate females. The curves for Byrsotria are based on 53 mated and 121 virgin females. The curves for Blaberus are based on 18 mated and 36 virgin females.
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Psyche
[December
lation of the corpora allata so that the oocytes develop rapidly (fig. 5) and oviposition occurs in 18 to 21 days (2=18.9dz0.40; - N=8). Copulation is completed in 17 to 30 minutes (x=20.4å±0.8 min. ; N=17). Of 22 females kept with males continuously, 19 mated 5 days after emergence; the other 3 mated after 6, 8, and 10 days respec- tively.
4.4
-
4.0 -
3.6 -
3.2
-
- -
s
2.8-
I
& 2.4:
2
LJ
_1
20
-
UJ
I-
& 16)
0
0
1.2
-
-
o = Oocytes, virgin females
= Oocytes, mated females
i = Degenerating oocytes, virgin females Fig. 5.
Growth of oocytes in mated and virgin females of Nauphoeta cinerea. Each point represents one female. Except for 2 individuals mated at 8 and 10 days of age, all others were mated when 5 days old. In a series of experiments performed at Harvard University, tem- perature was uncontrolled but usually higher than 24O to 25' C.; the insects were maintained on Purina Laboratory Chow. Both virgin and mated females oviposited earlier than in the above experiment but virgin females still oviposited later (24 to 35 days) than mated indi-
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Roth and Stay - Cockroaches
AGE OF FEMALE (DAYS)
Fig. 6. Effect of mating, starvation, and combined starvation and mating on oocyte development in Nauphoeta cinerea. The points are mean values; fed virgins, N1707; starved virgins, NX133 ; fed mated, NY58 ; starved mated, N=21. Females were mated when 4 to 6 days old, Vertical bars are one standard error (only positive halves of standard errors are indicated wherever errors overlapped) ; no vertical bars indicate standard errors of 2 0.02 mm. or less,
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176 Psyche [December
viduals ( I 5 to I 8 days). The difference in rate of oocyte development in virgin and mated females is shown in figure 6. The oocytes of stai-ved females that have mated develop at the same rate as fed mated females (fig. 6).
Of 17 virgin females that oviposited, 10 retracted the ootheca com- pletely into the uterus; several of these females abosted the egg cases several days after oviposition. Four females partly retracted the egg cases so that some of the eggs remained protruding from the abdomen; three dropped the egg cases while or after they were formed without retracting them. In most virgin females (including those that retract the ootheca normally) some mature oocytes remain in the ovaries. OVIPOSITION
OVIPOSITION
I
AGE OF FEMALE (DAYS)
Fig. 7. Ovarian cycle (first and second ovipositions) in Leucophaea maderae.
The points for the oocytes of unmated females (open circles) arc
means of 5 to 21-individuals (N=349).
For the first preoviposition period,
females were mated (solid circles) when 16 days old and each point repre- sents 1 individual. Each point for the gestation and post parturition periods represents one individual.
Leucophaea maderae: At emergence the oocytes of Leucophaea are 0.97d~0.01 mm. (N=Io). &lat~~re oocytes at ovulation are 5.56& 0.12 mm. (N=20: 10 mated and 10 virgin females). The new basal oocyte at oviposition is 0.66*0.o1 mm. (N= I I ) and at parturition I -05 k0.01 mm. (N=4). Under our conditions gestation lasted g I .8
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19621 Roth and Stay - Cockroaches I77
k0.7 days (Nz35) and the second oviposition occurred 27.8~0.3 days (N= 10) after parturition.
The ovarian cycle in this species is shown in figure 7. Llating shortens the egg maturation period so that the female ovulates at a mose or less definite time (fig. 3) after copulation (Engelmann, 1960). It is almost impassible to predict what the extent of oocyte development would be in virgins of known age (fig. 8). Only 25 of 381 mated females failed to oviposit. These wese 16 to 40 days old when mated and were dissected 30 to 62 days later. Eighteen had lasge degenesating 06cytes; 5 had small ( I .OI to I .73 mm.) and 2 had lai-ge but normal appearing oocj~tes. As Engelmann found mating 1-esults in the rapid growth of the oocytes (fig. 7). Of the lai-ge
number of virgin females dissected (fig. 8) onlj~ 2 had oocytes that wese degenesating.
0 = Oocytes, virgin females
Fig. 8.
Growth of oocytes in mated and virgin females of Leucophaea madcrae. Each point represents one female. Females were mated when 17 to 23 days old.
0.4
:
= Oocytes, mated females
0~00""~~"'l~"'l~"~0'~~5"~0"~5"~0"~5"~0"~5"~0"~5"~0"~5"~0"~5 AGE OF FEMALE (DAYS)
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178 Psyche [December
Of 47 virgin females that oviposited, only I I retracted the ootheca into the uterus; the others dropped the egg cases while they wei-e being formed. Virgin females frequently retain mature oocytes in theii- ovaries and the egg cases are incomplete (Engelmann, 1957a). Engelmann (1960) found that when females of Leucophaeu had constant access to males, mating occurred when their 06cytes avesaged I.Q~&O.OI mm. and none ~nated that had oocytes exceeding a size of I -46 mm. He concluded ( 1960, 1960a) that the corpus allatum hos- mone must be present in low titer for mating to occur, and as soon as a certain titei- is surpassed, the females did not mate even with ready access to males. We exposed females of various ages to males for relatively brief pel-iods (the longest time females were with males was 2 days), and measured the oocytes of those that did and did not mate. One hundred and fifteen females between 14 and 52 days of age were mated and their oocytes varied in size as follows: 1.08 mm. to 1-95 mm. (%=1.43*0.02, N=83) -
2.00 mm. to 2-97 mm. (x=2.34&0.06, N=21) 3.1 I mm, to '3.72 mm. (2=3.30*0.08, N= 9) 4-90 mm. to 5.88 mm. (5=5.39*0.49, N= 2) A breakdown of the data into two age groups when mated was as follows :
Size of oocytes (mm.)
when mated
Age (days) when mated and
number mated
As pointed out earlier our measusements are larger than Engel- mann's because in ous experiments the oocytes were dissected and measured in Ringer's solution whereas he measured fixed oocytes. The majority of the females mated when their oocytes averaged 1.43k0.02 mm. This value probably corresponds to Engelmann's mean of 1-08 k0.01 mm. However, 28% of the females mated when their oocytes were more developed. Thii-ty-six females that failed to mate when exposed to males along with the above females that copulated had oocytes that ranged from 1.01 to 1.68 mm. (<=I.I~&o.o~ mrn.; Nr25) and 2.05 to 5.88 mm. (i=4.54&0.38 mm.; N=I I). These was a slight but not very significant shortening of the inter-
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19621 Roth and Stay - Coch-oaches I79
va1 between age at mating and age at ovulation when older females mated (Engelmann, I 960). Engelmann suggested that this shorten- ing of the period needed lor egg maturation could be explained by the presence of larger amounts of reserve substances that would allow for more rapid growth of the eggs and might not be due to the PI-esence of largei- oocytes at the later mating. Our findings confirm Engel- mann's in that Leucophaeu tend to mate moi-e readily when their 06cytes reach a certain size. However, some females mate even though their oocytes have grown beyond this ci-itical size and the shortening of the period between mating and ovulation is undoubtedly due to the presence of large oocytes in these older females; some females mate even when there is a high titei- of corpus allatum hormone (as indi- cated by lai-ge oocytes).
Engelmann ( 1960) found that when the nesve coi-d of Leucophaea was severed o to 2 days after mating, oocyte maturation occurred about a week later than normal mated females. When the cord was severed 3 to 19 days after mating, the females oviposited at the same age as noi-mal mated females indicating that an intact nesve cord is necessary for at least 2 days after mating for the mating stimulus to be effective. When the nerve cords of virgin females were severed and they were not mated, ovulation occurred at the same time as females that had their nerve cords severed o to 2 days after mating. Engelmann concluded that severance of the ventral nerve cord in virgins either stimulates the corpora allata or cuts off an inhibitory center foi- the corpora allata but he favoi-ed the latter hypothesis. We severed the nerve coi-ds of females prior to mating them and found that in most cases the spei-matophose was not inserted properly. Of 27 females that mated after their nerve cords were severed, only 8 had spermatophores that were appai-ently transferred by the male normally. Four females had spesmatophoses that were visible in the genital region but they had not been inserted properly in the bursa. In one mating the spermatophore was dropped by the male without being transferred to the female. Fourteen females had no spermato- phores after mating and originally it was believed that none had been transferred by the male. However, it was discovered that in some females the male pierced the wall of the utei-us and inserted the sper- matophore in the body cavity near the right ovary (fig. 13C). This was found in 7 females but may have occurred in 6 others that appar- ently had no spermatophore inserted but were not dissected because we did not realize that the spermatophore could be inserted into the body cavity. One female had no spermatophore after mating, based on dissection. It seems that the female takes an active role in the
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= Oocytes,moted femoles o = Oocytes, virgin females .=Degenerating oocytes, virgin females
Bhberus giganteus
AGE OF FEMALE (DAYS)
Fig. 9.
Oocyte development in mated and virgin females of Blabem. Each point represents one individual. Females of B. craniifer were mated when 1 to 16 days old. Females of B. giganteus were mated at 19 to 35 days of age and all were ovipositing when their oocytes were measured.
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19621 Roth and Stay - Cockroaches 18 i
proper positioning of the spermatophore in the bursa copulatrix, and an intact nerve cord is needed for proper muscular movements of the female genitalia. Of I I nerve-cord-severed virgin females that ovi- posited 7 dropped their egg cases when they were formed and 4 re- tracted the ootheca into the uterus but aborted some time later. Blaberus craniifer: The growth of the oocytes of virgins is rapid but mating affords sufficient additional stimulation (fig. 9) so that ovulation occurs about a week earlier than in unmated individuals (fig. 4). Eighteen mated females oviposited in 19 to 29 days (x= 23.920.6 days) ; sixteen oviposited normally, I dropped its ootheca and I failed to retract the egg case completely. Virgin females ovi- posited in 18 to 41 days (%=32.0å±0.8 N=36). Stimulation from mating results in either an additional production of gonadotropic hor- mone or it may possibly serve as an oviposition stimulus. The relation- ship of age at mating and age at oviposition of the female is similar to that found in Byrsotria (fig. 3). The older the female when mated the shorter the interval to ovulation indicating that the oocytes of these older females are large when mating occurs. Of 40 virgin females that oviposited 23 (58%) failed to retract the egg case completely and some of the eggs protruded beyond the abdo- men. This may be due to the fact that in some females the eggs are not aligned properly in the ootheca and may even be arranged in 3 rows (rather than 2) which may make it difficult to retract the egg case completely into the uterus. Generally, in most virgin females that ovulate, the proper amount of colleterial gland secretion does not flow out over the eggs since the accessory glands are usually quite full even after the egg case is formed. Sometimes not all of the eggs are laid and mature oocytes remain in the ovaries and are eventually resorbed. Thirteen females retracted the ootheca normally into the uterus. Four females dropped the ootheca although some eggs remained in the uterus. Perhaps this is related to the lack of proper amount of col- leterial gland secretion being poured out around the eggs; the result may be the formation of a weak ootheca which cannot support the weight of the eggs as they are extruded some distance beyond the end of the abdomen prior to their being retracted. In addition to the above 40 females, 5 unmated females that did not oviposit in 46 to 51 days had oocytes that had obviously matured (based on size) but were degenerating.
Six allatectomized virgin females that had not ovulated had cor- pora allata implanted at 62 to 82 days of age; all 6 oviposited within 31 days after implantation. Nine allatectomized virgin females kept for 66 to 238 days failed to ovulate.
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182 Psyche
[December
All the nerves to the corpora allata were severed in I I virgin females and the glands were left in the animals; ten oviposited in 21.820.49 days which is similar to ovulation in mated females. This would indicate that the brain tends to inhibit the corpora allata in virgin B. craniifer and mating overcomes this inhibition. Blaberus giganteus: The oocytes of virgins grow and yolk is de- posited but after about a month they may degenerate unless mating occurs (fig. 9). In general mating appears to be necessary for comple- tion of oocyte development, at least more so than in B. craniifer. Fourteen females kept with males until mating occurred, mated at 8 to 35 days of age and oviposited when 35 to 51 days old (xz42.6 k 1.3 days). Of 8 virgin females, not shown in figure 8, kept for 51 to 68 days, only 2 oviposited when 51 days old, and in both individuals the oothecae were dropped and not retracted; the 6 females that did not oviposit had small abnormally shaped oocytes that failed to de- velop.
'The relationship between age when mated and age at ovulation (fig. 3) appears to be similar to Byrsotria and B. craniifer rather than Leucophaea.
The females of B. giganteus which have continuous access to males, mate over a rather wide age range, and their oocytes may vary considerably in size at the time of mating. Thirteen of 14 virgin females that had all the nerves to the corpora allata severed at 0 to 19 days of age ovulated in 35.1k1.2 days after the operations ; one oviposited I 53 days after the operation at I 63 days of age. Severing the connectives to the corpora allata apparently removed the inhibition from the brain.
The effects of mating vary in degree among the species of cock- roaches that incubate their eggs internally or carry them externally during the incubation period. In the summary given below, data from Engelmann, ( 1957, 1959, 1960), Roth and Willis ( 1961) Roth and Stay ( 1961, 1962), and the present study have been used. I. Effect of mating on oocyte development. I. Oocytes of virgins may degenerate :
a. before reaching ovulation size (Nauphoeta cinerea and Blaberus giganteus)
b. before or after reaching ovulation size (Byrsotria fumi- Mating prevents degeneration of the oocytes in the above 3 species. The oocytes of virgins generally do not degenerate in Blaberus craniifer (rarely), Diploptera punctata, Leucophaea maderae, Pycnoscelus surinamensis (parthenogenetic and bi- sexual strains) , BZatteZZa germanica, and B lattella vaga.
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Roth and Stay - Cockroaches
183
2. Mating increases rate of oocyte development so that the first preoviposition period is less than in virgin females. Preovi- position period shortened on an average of about: a. I day (Pycnoscelus s'unnamensis, bisexual strain; Blattel- la).
b. 9 01- more days (Blaberus craniifer, Blaberus giganteus). c. I 7 days (Nauphoeta cinerea).
d. 30 or more days (Leucophaea maderae). e. Majority of virgins do not oviposit for months or not at all.
Oviposition occurs about 10 days after mating (Di- ploptera punctata) .
3. Mating apparently has little effect on the rate of oocyte development but may stimulate oviposition (Byrsotria fumi- gata).
4. Mating has no effect on rate of oocyte development or on the length of the preoviposition period (Pycnoscelus surinamensis - parthenogenetic strain mated to males of the bisexual
form).
Effect of mating on ovulation and oviposition. I. Ovulating virgins frequently retain mature oocytes in some part of the reproductive tract so that not all of the eggs are laid (BZaberus craniif er, Blattella vaga, Byrstotria fumigata, Leucophaea maderae, Nauphoeta cinerea, Pynoscel,us surina- mensis bisexual strain).
Mated females usually oviposit all of the mature oocytes. 2. Ootheca is incompletely formed and oviposition is abnormal in a large percentage of virgins.
a. Ootheca usually dropped when formed (Leucophaea ma- derae, Pycnoscelus surinamensis [bisexual strain], Blattel- la vaga).
b. Ootheca dropped or partly retracted into the uterus (Nau- phoeta cinerea).
c. Ootheca usually only partly retracted into the uterus so that some of the eggs protrude from the end of the ab- domen (Blaberus craniif er) .
Mating in a large percentage of females results in normal forma- tion of the ootheca and complete retraction of the egg case into the uterus in the above species.
3. Ootheca may be retracted normally into the uterus in a high percentage of virgins (Byrsotria fumigata, Diploptera punc- tata, and Nauphoeta cinerea) .
4. Mating has no effect on normal oviposition (Pycnoscelus
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Psyche [December
surinamensis - parthenogenetic strain mated to males of the bisexual form) .
From the preceding summary one finds two extremes of dependence upon mating for stimulation of the corpora allata. In Diploptera, the majority of females require mating for maturation of the oocytes and its effect is the most striking since ovulation occurs about 10 days after mating, whereas virgin females may go for months without ovi- positing or they may never do so (Engelmann, 1959, 1960; Roth and Stay, 1961). At the other extreme is the parthenogenetic strain of Pycnoscelus surina~nensis where mating is unnecessary and the oocytes mature in virgins about 13 days after emergence. In this species some newly-emerged females already may have yolk in their oocytes. Be- tween these two extremes are species which show varying degrees of dependence on external mating stimuli for overcoming inhibition of the corpora allata. The oocytes in virgins grow but unless mating occurs the ovarian eggs do not mature and may degenerate before reaching ovulation size. This is particularly true in Nauphoeta, Byrsotria, and Blaberus gigantew and apparently in these species the corpora allata in many virgin females secrete an insufficient amount of hormone for the oocytes to mature; and in many of these females the partly developed oocytes are not maintained but degenerate unless the corpora allata are stimulated by mating. Various species show different degrees of dependence on mating for normal formation and retraction of the ootheca into the uterus. This is of particular interest, for the ability of virgin females to place the ootheca in the brood sac is a prerequisite to the evolution of partheno- genesis in false ovovivipasous cockroaches (Roth and Willis, 1961). Not all females of a species behave similarly which explains why some forms are included in more than one category in the above summary. It is this variation in behavior which may make possible the evolution of parthenogenesis in bisexual species of cockroaches. From the few species studied one can arrange the forms in a series to show the gradu- al evolution of retraction of the ootheca into the uterus in virgin females, although we do not imply that one gave rise to the other. Almost invariably in the bisexual strain of Pycnoscelus surinamensis the ootheca is dropped at formation in virgins. In Nauphoeta the
ootheca is dropped at formation, partly retracted, or completely re- tracted. In Blaberus craniifer the ootheca is usually only partly retracted into the uterus. In Byrsotria the ootheca of virgins that ovulate is usually normally retracted into the brood sac. Although
parthenogenesis is uncommon in false ovoviviparous cockroaches (other than the parthenogenetic strain of Pycnoscelus) it does occur
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19621 Roth and Stay - Cochroaches I 85
rarely. Nine females of Nmphoeta cinerea had eggs that developed parthenogenetically and in 8 individuals the eggs hatched; two un- mated females that developed from unfertilized eggs gave birth to 3 nymphs (Roth and Willis, 1956). We have encountered only one case of parthenogenesis in Leucophaea (20 undeveloped eggs and 5 well developed embry~s with pigmented eyes in an ootheca 89 days after ovulation) and one in Byrsotria (2 well developed embryos, 55 days after oviposition) ; Barth (persond communication) has reared a single adult female of Byrsotria that was produced parthenogenetic- ally. Only one unmated female of the bisexual strain of PycnosceZus was found that had a developed embryo in one of the eggs of the ootheca (Roth and Willis, I 961 ) . Parthenogenesis in false ovovivi- parous cockroaches depends upon ( I) the ability of virgin fernales to mature their oocytes, ovulate, and form and retract the ootheca into the uterus, and
(2) the capacity for unfertilized eggs to develop. Although parthenogenesis cannot occur unless the above requirements are met, the insects must first be capable of retracting the ootheca into the uterus for unless this occurs the eggs desiccate since the o~theca does not prevent water loss in cockroaches that incubate their eggs internally (Roth and Willis, I 955).
No experiments were performed on the species, in this study, to determine the mechanism of stimulation during mating. However, in Leucophaea (Engelmann, 1960) and DipZoptera (Engelmann, 1959, 1960; Roth and Stay, 1961) it is a mechanical stimulus that activates the corpora allata and it is probably similar in Pycno~ceZus (bisexual strain), Nauphoeta, and BZaberus.
Food intake and maturation of the oocytes Food intake stimulates maturation of the oocytes in Leucophaea (Scharrer, I 946 ; Joha~~sson~ 1955 ; Engelmann, I 960) and BZatteZZa germanica and B. vaga (Roth and Stay, 1962) but is unnecessary for oocyte development in DipZoptera (Engelmann, 1960; Roth and Stay, 196 I ) . The effect of starvation on oocyte development in several species used in this study was deter~nined; all females were isolated from food at emergence.
PycnosceZus surina7nensis: Fifteen females of the parthenogenetic strain were starved without water. All oviposited in 14. I k0.4 days, which was about I day more than in unstarved females (table I). Nine virgin females of thc bisexual strain starved without water ovi- posited in I 4.3 e0.5 days, which was similar to unstarved individuals (cf. table I). Food is unnecessary in both strains to activate the cor- pora allata or for maturation of the eggs for the first ovulation.
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I 86 psyche [December
Nm$koeta cinereu: The effect of starvation on &cyte development in iVm#hocta is shown in figure 6. The oiicytes of starved virgi females develop more slowIy and to a lesser degree than those of fed virgin females. When starved females were mated the okytes matured in the same period as fed mated females. In Lcwophaea, females that were starved but mated failed to deposit yolk in the 06cytes and Engel- mann ( 19b) concluded that the brain properly integrated the difier- ent afferent stinidi (inhibitory during starvation and activating from mating) into messages to the corpora allata and the endocrines were not activated. Nauphoetu differs from L.mco+haeu in that the oocytes of starved females become well developed and mating adds sufficient stimulation to the corpora data for the oocytes to mature nomaIIy in spite of the absence of fwd.
Blaberus craniifer: Seven virgin females of Bhbcms craniijer were starved (with water) for 22 to 39 days. 111 6 femdes the oocytes measured 4.82&0.19 mn. ; one female had wcytes that did not dc- vdop ( I -38 mm.) . The o?icyws of fed females 22-38 days of age were 5-61 20. I I. AIthougli there may be a slightly slower rate of growth of the o6cytes in starved females, food is unnecessary for initiating activity of the corpora allata.
Eyrsotria fumigata: Twenty-four virgin Byrsotria were starved (with water) for 20 to 45 days. Six females starved 20 to 24 days had &ytes 4.22e0.35 mm. long, Eight sta~ed 29 to 40 days had oikytes 4.86k0.36 mm. in length (several had Gcytes that had begun to degefieratc). Two females had mall undeveloped Gcytes (0.88 k0.01 mm.} and 8 had small, round, abnonnalIy shaped okytes. Thirtythree virgin females were starved without water for 26 to 50 days. Nine (starved 26 to 43 days) had oocytes 5.01 &a30 mm. long. Twelve had large Gcytes that were degenerating. Five fen~aIes ovi- posited in 34 to 38 days; four had undeveIoped &ytes ( 1.14k0.08 mm.) and 3 had small abnormally shaped Gcytes. The a6cytes of virgin females fed for 20 to 24 days &-ere 4.85 k0.32 (N=17) and for 29 to 40 days, 6.36+0.22
(N=39). Although the okytes of
starved females may not grow quite as rapidly as unstarved individu- als, neither food nor water are necessary for growth of the 06cytes in Byrsotk.
The dtgrw to which cockroaches depend upon food intake for stim- ulation of the corpora aha varies among the species. The forms may be arranged in a series showing comp1ece dependence to complete independence upon food $or oticyte development. The effects of star- vation may be summarized as fo1lows:
1. Okytes do not develop (Leuco$haea, Bhttelh gcrnzanica, and Biatteh vagu).
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19621
Roth and Stay - Cockroaches
2. Oocytes develop but at a slower rate and to a lesser degree in fed females (Nauphoeta).
3. 0,ocytes develop at a normal or slightly slower rate than 187
than
fed
females (Blabems craniifer, Byrsotria) . 4. Oocytes mature about as rapidly as fed females (Diploptera, FycnosceZus ~urinamensis - bisexual and ~ai-thenogenetic strains).
Inhibition of the corpora aZZata during pregnancy During the first gestation the basal oocytes, in a11 of the species in- vestigated in this study, usually remain undeveloped except for a small increase in length; some Nauphoeta females may have oocytes con- taining yolk at parturition. Yolk deposition occurs in these basal oocytes only after parturition (except in Diplofitera and some Nau- phoeta). This has already been pointed out in PycnosceZus (fig. I). Very similar cycles occur in BZatteZla (Roth and Stay? 19621, Leu- cophaea (Engelmann, 1957) and DipZoptera (Engelmann? 1959; Roth and Stay, 1961 ) . However in DipZoptera the oocytes begin to show deposition o'f yolk about 3 days before parturition (Engelmann, I 959 ; Roth and Stay, I 961 ) . Although complete ovulation cycles are not given for BZaberus, Byrsotria, and Nauphoeta, measurements of the new oocytes at ovulation, and at parturition show that inhibition of the corpora allata during gestation also occurs in these, forms. In Leucophaea ( Engelmann, I 957, I 9601, DipZoptera (Engelmann, 1959 ; Roth and Stay, 1961 ) , and PycnosceZus (Roth and Stay, 1959) removal of the ootheca results in resumption of growth of the oocytcs prematurely, indicating that the ootheca in the uterus, in some man- ner, inhibits the activity of the corpora allata. The following expei-i- ments were performed to investigate the nature of inhibition of the corpora allata during gestation.
PycnosceZus surinamensis: The 06thecae were removed from 84 females of the parthenogenetic strain, 62 (74% ) of which subsequent- ly ovulated. Of the 22 females that failed to oviposit 25 to 37 days after the operation, 15 had oocytes that showed essentially no develop- ment (0.64 to 0.79 mm.) and 7 had oocytes with definite yo'lk deposits (0.84 to 2-39 mm.) ; one female had oocytes that had apparently matured but had not been laid and were being resorbed. There is an inverse relationship between the age of the ootheca at the time it is removed from the uterus and the time required to ovulate again. Less time is required to ovulate again, the older the uterine eggs are when removed (fig. 10). This relationship also has been found in BZatteZZa and DipZoptera (Roth and Stay? 1961, 1962). One
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188 Psyche [December
of the factors which might account for this may be that the oocytes increase in size during gestation so that at the time an older ootheca is removed the oocytes are larger when again subjected to gonadotropic hormone. The larger oocytes may contain greater amounts of reserve substances allowing for a more rapid maturation of the eggs. Since the period between the first and second ovulations is about 70 days (table I) it is evident from figure 10, showing the relatively AGE (DAYS) OF OOTHECA WHEN REMOVED FROM UTERUS Fig. 10.
Relationship between the age of the ootheca at the time it was removed from the uterus of Pycnoscelu~ surinamcnsis (parthenogenetic strain) and the time required to form a new ootheca. Each point represents one individual. The points at 53 to 58 days on the x axis, are for females that gave birth normally; all of the other points are based on females that had their oothecae removed manually.
sapid development of the oocytes (as indicated by oviposition) after removal of the ootheca, that the oocytes are inhibited bj7 the presence of the eggs in the uterus.
Virgin females of the bisexual strain of PycnosceZus almost invari- ably fail to retsact their oothecae into the uterus (Roth and Willis, 1961 ) . Foul-teen virgin females that had dropped their oothecae when they were formed, oviposited again in 28 to 39 days (%=32.9&1.1 days). The normal interval between the first and second ovulations in this strain is about 67 days (53 days of gestation plus 14 days postparturition, table I) and the absence of uterine eggs in the brood sac resulting from aberrant oviposition hastened the development of
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19621 Roth and Stay - Cockroaches 189
the oocytes. Three mated bisexual form females that failed to reti-act their oothecae also formed the second egg case in 30.3k2.7 days. Three mated females that had their oothecae removed 2) 5, and 7 days after oviposition ovulated again in 32 to 33 days. Both sti-ains of Pycnoscelus are similar in that the presence of an ootheca in the uterus inhibits the development of the oocytes. Leucophaea maderae: The oothecae were removed fi-om 102 preg- nant females at different stages in pregnancy to determine the time required for the next ovulation. Forty-three females oviposited during the pesiod of the experiment and these results are plotted in figure I I. As in PycnosceZ,us the time required to ovulate aftei- removal of the ootheca varied with the age of the ootheca when it was removed; the younger the olotheca the longer it took to mature the oocytes. Of the remaining females) 45 showed little or no growth of the oocytes; those whose oothecae wei-e removed o to 18 days after ovulation had oocytes 1.061ko.03 mm. (N=22)) 62 to 82 days later and 23 females whose AGE (DAYS) OF OOTHECA WHEN REMOVED FROM UTERUS Fig. 11.
Relationship between the age of the ootheca at the time it was removed from the uterus of Leucophaca maderae and the time required to form a new egg case. The points plotted at 82 to 97 days on the x axis are for females that gave birth normally; all of the other females had their 06thecae removed manually. Each point represents one female.
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Psyche
[December
oothecae were removed 23 to 76 days after oviposition had oocytes I. 19 k0.04 mm., 34 to 63 days later. Fourteen females that had their oothecae removed o to 77 days after ovulation had developed oocytes 3.72k0.30 mm. long, 34 to 71 days later. It is unknown why about 45% of the females failed to show W t e development after removal of the ootheca; the presence of degenerating wcytes that were not laid in the first ovulation may account for some of these cases. Byrsotria fumigate: In Byrsotria gestation lasts from 71 to 82 days ('X.=76.2-+- I .4; N=6). The basal okytes at parturition vary in length from 1.43 rnm. to 1.71 mm. (Z::=I.~~å±O.O mm.; N~ro). The second ovulation occurs 21 to 30 days (Z=24.8å 1.6; N=5) after parturition. Oocyte development during pregnancy in mated females is inhibited and no yolk is deposited until after the young are born.
Five mated females had their Gthecae removed at various periods during pregnancy. One whose ootheca was removed 27 days after ovulation oviposited 45 days later. Two females whose Gthecae were removed 28 and 40 days after oviposition had practically mature Gcytes, 5.98 mm. and 6.22 mm. (fig. uB) respectively, 32 days later. The oocytes ( 1.23 and 1.29 mm. long) of two females whose oothecae were removed on the first and thirty-first day of pregnancy failed to develop when examined after 75 and 32 days. The 6thecae of 10 virgin females were also removed with the following results. Three females whose oothecae were removed 29 to 34 days after ovulation had mature otkytes that were being resorbed 53 days later. One female whose ootheca was removed 38 days after oviposition ovulated again 39 days later. Six females whose Gthecae were removed from 1 to 24 days after oviposition failed to develop their oocytes (Z= I .53 dto.05 mm.) when examined 35 to 59 days after the operations. In the mated and virgin females that failed to develop Gcytes after removal of the oothecae, several unlaid degenerating ciicytes were present from the previous ovulation which may account for the results. Virgin females of Byrsotria that deposit their unfertilized eggs noi-mdly in the brood sac frequently carry these Sthecae for a longer period of time than mated females. When the undeveloped eggs are finally extruded the ovarian Gytes may be large and contain consid- erable yolk in spite of the fact that an Stheca was present in the uterus during the entire "pregnancy" period. Thirteen females that carried their unfertilized eggs for 71 to 90 days had okytes 1.51 k 0.04 mm, which is normal far the size of the oocytes at parturition of mated females. However, the okytes of 14 virgins that had carried their oothecae for 87 to 97 days had oocytes that varied in length from
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19621 Roth and Stay -- Cockroaches 191
2.86 to 6.12 mm. (Z=4.60å±0.2 mm.). One mated female that aborted an ootheca with undeveloped eggs after carrying for 79 days had oocytes 3.72 mm. long. It is apparent that toward the end of the "gestation" period in virgin females or once the time at which parturi- tion should normally take place is passed, the inhibition of the corpora allata (due to the presence of the ootheca in the uterus) breaks down and these endocrines again secrete the gonadotropic hormone. Eleven virgin females that aborted their oothecae 91 to 104 days after ovi- positing, were kept until they ovulated a second time. Five of the females oviposited in 21 to 30 days (?=25.6å±1.6 which is the same as mated females indicating that their oocytes at the time of aborting were relatively undeveloped. The other 6 virgin females ovulated in I 1 to I 8 days (%= I 4.8å I .4) undoubtedly because their oocytes were already well developed when the egg cases containing undeveloped eggs were extruded from the uterus. Blaberus craniifer: The oocytes of this species at emergence are about 1.39 to 1.44 mm. (N=2) in length. The mature oocytes are about 6.12 to 6.37 mm. (Nz3) and at oviposition the new basal oocytes vary from I .02 to I. I 6 mm. (Z= I .09å±0.0 ; N=7) . At parturition the oocytes are 1.34 to 1.85 mm. (?=1.56=1=0.07 ; N= 6). Gestation lasts 73 to 87 days (Z=79.2å±2.4 N=5). After birth, a second ovulation occurs in 16 to 27 days (%=22.0å±1.9 Six virgin females had their oothecae removed on the day of ovi- position.
One oviposited again 47 days later. The others were dis- sected 44 to 60 days later and all had well-developed oocytes (3.96k 0.43 mm.). One female whose ootheca was removed 8 days after ovulation had oocytes 5.88 mm. long, 54 days later. Two females whose oothecae were removed 73 days after oviposition (i.e. close to parturition in mated females) had oocytes 3.23 mm. and 3.82 mm. long, only 10 days later. Removal of the ootheca in B. craniifer results in renewed development of the oocytes.
The principal evidence for Engelmann's (1957) hypothesis that a hormonal factor from uterine eggs inhibits the corpora allata via the brain was his claim that implantation of uterine eggs into the abdo- men of females of Leucophaea inhibited oocyte development, and nerve cord severance of pregnant females only had a slight but tem- porary effect on growth of the oocytes. However, more recently, Engelmann (1960) found that severance of the nerve cord in preg- nant females results in growth of the oocytes indicating that nervous stimuli may also be responsible for inhibition of the corpora allata during pregnancy.
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1 92 Psyche [December
We have repeated these and performed additional experiments on the following species of cockroaches:
Pycnoscelus surinamensis (parthenogenetic strain) : Some of the experiments on this species were briefly described elsewhere (Roth and Stay, 1959). The ootheca was removed from the uterus of each of 10 females I to 16 days after oviposition and one-half of each ootheca was implanted into the body cavity of the donor female. Twenty-three days after the operation the oocytes ranged in length from 2.12 mm. to 3.19 mm. (2~2.70k0.10 mm.) clearly larger than the o6cytes of females that have been pregnant for 24 to 39 days which vary from 0.59 to 0.66 mm. Implantation of uterine eggs into the abdomens of females that had their oothecae removed did not prevent subsequent growth of the oocytes. Two of the 10 females had oocytes that had practically matured and the oocytes of the remaining 8 females were approaching maturity (2.97 to 3.36 mm., cf. table I) and undoubted- ly would have matured in about die time one would expect ovulation following removal of the ootheca (cf. fig. 10). One-half of young oothecae were implanted into the body cavities of 6 females one day old or less; after r I days the oocytes were 2.65 to 3.14 mm. (x^ 2.9 I 20.10) in length. The oocytes of untreated I I-day old females averaged 2.93ko.06 mm. (N= 10). These results show that uterine eggs when implanted into the abdomen of a recently emerged female have no effect on the initial development of the oocytes. Nor does implantation of uterine eggs into the abdomen of a female that had her ootheca removed inhibit subsequent development of the oocytes. The oothecae of 20 pregnant females were removed 13 to 25 days after ovulation and a wax "ootheca" about the size and shape of a normal ootheca was inserted into the uterus. Examined 20 to 37 days later all had small oocytes (fig. 13A) similar in size to those found in females that were pregnant for 36 to 52 days (table 3). However EXPLANATION OF FIGURE 12
Fig. 12A. Pycnoscelus surinamensis (parthenogenetic strain). Ootheca (upper) and ovaries (lower) of a female that had been pregnant 60 days and whose nerve cord was severed on the thirty-second day of pregnancy. When dissected 28 days after the operation, the embryos in the ootheca began to hatch. The oocytes in the ovary had matured but were being resorbed. (Note the abundant colleterial gland secretion [arrow]). Vertical lineÌÔ mm.
Fig. 12B, 12C. Blaberus craniifer. B. Mated female whose nerve cord was severed 26 days after oviposition. The ootheca (0) containing well developed embryos (note pigmented eyes) was being aborted 34 days after the operation. The oocytes (arrow) were 5.88 mm. long.
C. Virgin female that had carried
an ootheca with undeveloped eggs for 93 days (well beyond the normal gesta- tion period). The oocytes were 3.92 mm long. Vertical lineÌÔ mm.
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19621 Rath and Stay - Cockroaches 193
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Table 3 - Effect of inserting a wax "ootheca" into the uterus and subsequent nerve cord severance on oocyte development in the parthenogenetic strain of Pycnoscelus surinamensis AGE (DAYS) OF OOTHECA
WHEN REMOVED AND WAX
WAS INSERTED INTO
UTERUS
13-25
Control (ootheca
in uterus)
Nerve cord severed
after insertion of
wax
15
15
I3
Control (Gtheca
in uterus; nerve
cord intact)
IAYS AFTER
NSERTION OF
VAX, OOCYTES
VERE MEASURED
)AYS $ HAD
~OTHECA OR
~OTHECA THEN
VAX IN UTERUS
OCYTES (MM.)
IEAN k S.E.
Numeral in ( ) =number of days, prior to measuring oocytes, nerve cord was severed.
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19621 Rdh and Stay - Cockroache~ 195
Fig. lL%-B. Pjrnorcdi~s snr;r~nrn/ms~~ (parthenogenetic wain), Ovaries
(01 undeveloped
thc resdr of the presence of a wax %otheca" in the uterus (u). The 06theca was removed on thc thirteenth day of preppanv, and replaced with wax. The female was diwected 37 days later. B. Oocytes which developed in a femaTe that had a wax "ootheca" in it8 uterus for 37 days. The obtheca was removed 13 days after avubtion and replaced hy wax. Twentyfour days later the nerve cord was severed and the female was dissected 13 days later,
Fig. 13C. f~mcopbuca muderae. Dissection of a female that mated after her nerve cord had been transected. The apermatophore (9) was inserted by the male into the body cavity neat the right ovary (arrow),
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196 Psyche [December
Table 4 -Effect of nerve cord severance on oocyte development in the parthenogenetic strain of PycnosceZus surinamensis DAYS AFTER
OVIPOSITION NERVE
CORD WAS SEVERED
< 1
4
< 1
o1
< 1
< 1
27-32
Con ti-01s
(sham operated)
= -4
< 1
I
IAYS AFTER
IPERATION
IOCYTES WERE
fEASLRED
)OCYTES (AM.)
dEAN & S.E.
2.08 k0.07
2-94
2-57 k0.30
3 .0b2
3.52k0.16~
2-94
Oocytes matured
and degenerating3
'Opesated on just after the female retracted the ootheca. 200cytes matured.
'The uterine eggs of these females were completely developed and parturition was imminent. The eggs began to hatch (fig. IZA) from 3 of the 5 females after their oothecae were removed from the uterus. when the nerve cords were severed in five females that had been carry- ing a wax '(ootheca" in the uterus for 24 days, the oikytes we11 developed (fig. I 3B) S to I 3 days Iatei- (table 3). The effect of nerve cord severance in pregnant females on develop- ment of the oocytes is shown in table 4. The oocytes could mature (2.97 to 3.36 mm., table I), in females carrying oothecae once the nerve cord was severed. The time required for the oocytes to mature in pregnant nerve-cord-severed females was essentially the same as that taken by females after their oothecae were manually removed. When removed at o days a new ootheca was formed in about 28 to 31 days. JVhen removed after 27 to 32 days of pregnancy ovulation occurred about 22 to 25 days later (fig. 10). The five females that had their nerve cords severed 27 to 32 days after oviposition all had mature oocytes that were degenerating or being resorbed 23 to 33 days later at the time the uterine eggs were ready to hatch (fig. IzA). Apparently oviposition could or did not occur while an ootheca was
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19621 Roth and Stay - Cockroaches 197
in the bi-ood sac, and the mature ciicytes degenerated. In addition to the fifteen females shown in table 4, two females had their nerve cords severed prior to ovulation and oviposited normally; 24 and 25 days later their oocytes had grown considerably and were 2.18 mm. and 2.72 mm. respectively. The nerve cord may be severed at any site between the second and sixth segments to eliminate the inhibition of the corpora allata during pregnancy. Two females had their nerve cords severed between the second and third abdominal segments 4 days after oviposition; 29 days later their oocytes were 2.75&0.01 mm. Six females had their cords severed between the third and fourth) fourth and fifth or fifth and sixth abdominal segments, 4 days after oviposition; 22 days later their oocytes were 1.8920.24 mm. long. Six pi-egnant females taken from cultures (histories unknown) had their nerve cords severed between the fourth and fifth, or fifth and sixth segments; 20 days later their o6cytes measured 2.28k0.33 mm. Unmated females of the parthenogenetic sti-ain oviposited normally in 98 percent of 248 individuals examined (Rot11 and Willis) 1961). Twenty-two females had their nerve cords severed prior to oviposition. Of these) 15 (68%) ovulated in the normal period of time and de- posited eggs in the uterus; 8 oviposited all theis eggs and had normal 06thecae but the othes 7 had small abnoi-mally shaped oothecae and fsonl I to 12 mature oocytes 1-e~nained in their ovaries. The remaining 7 of the 22 females operated upon failed to retract the ootheca into the brood sac; in 4 of these one or more mature oocytes remained in the ovasies but in the others all the eggs were laid. Of 9 females that were sham-operated when I to 4 days old, all oviposited normally and no mature oocytes 1-emained in theii- ovaries. Apparently an intact nerve cord is necessary for normal deposition of mature 06cytes and for nosmal formation and retraction of the egg case in some females of P. surinamensis (parthenogenetic strain), Some centes, possibly in the brain) may be involved in this behavior. Virgin females of the bisexual sti-ain almost invariably fail to retsact their 06thecae into the uterus (99% of 138 females, Roth and Willis, 1961) and drop the incompletely formed ootheca. Thirteen virgin females had their nerve cords severed when I to g days old. All ovi- posited abnormally) which is the typical behavior of virgins of the bisexual strain; 10 dropped their oothecae and all had mature oocytes left in their ovaries. The other 3 carried their otithecae extruding from the abdomen but failed to reti-act them; 2 had some mature oocytes left in the ovaries but the third had none. Virgin females of the bisexual strain with severed nerve cords behaved like unoperated virgin females in oviposition and deposition of mature 06cytes.
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198 Psyche
[December
In BZatteZZa pressure on the oothecal chamber by the ootheca ap- pears to be responsible for the inhibition of the oocytes, the stimulus being transmitted via the -nerve cord (Roth and Stay, 1959, 1962). When the ootheca is in the uterus of Pycnoscelus the ovipositor is bent forward and is held in that position by the egg case. This suggested the possibility that the gonapophyses might be involved in transmitting nervous stimuli to the brain which then inhibits the corpora allata. Two experiments on Pycnoscelus were performed to test this hypothesis. Glass beads (3-3.5 mm. in diameter) were insert- ed into the vestibule of 7 females I to 2 days of age. A small drop of ferrule cement on the anal segments prevented the beads from being extruded; the beads exerted pressure on the ovipositor. The oocytes
were measured at 3 different periods. At 5 days of age they were 1-77 k0.13 mm. (N=4), at 7 days, 2.20 mm. (N=I), and at 13 days, 2.85k0.01 mm. (N=2).
Normal females at 5, 7, and 13 days of
age had 06cytes 2.03k0.08 mm. (N=9), 2.28k0.08 nxn. (N= IS), and 2.94&0.04 mm. (N=6) respectively. The presence of a
bead and the resulting pressure on the ovipositor of recently-emerged females had essentially no effect on the development of the oocytes. To determine if release of pressure by the ootheca on the ovipositor during gestation would result in resumption of oocyte development, the o6thecae of pregnant females were partly extruded, a portion of the egg case was cut off and the remainder was pushed back into the uterus. This was done to 8 females I I to 12 days after oviposition and their oocytes were measured on the fifty-fourth to fifty-sixth days of pregnancy when the females gave bii-th or parturition was immi- nent. Five operations were successful in that the ovipositors were EXPLANATION OF FIGURE 14
Fig. 14.
Reproductive organs of Byrsotria fumigata. A. Normal mated female sham operated (nerve cord) when pregnant 38 days and dissected after 70 days of pregnancy. The eggs (arrows) in the ovaries are undeveloped; UKuterus containing ootheca. B.
Mated female whose ootheca was removed 40 days after oviposition and dissected 32 days later. The eggs in the ovaries have almost matured (6.22 mm. long).
C.
Mated female whose nerve cord was severed at 39 days of pregnancj and dissected 32 days after the operation (71 days pregnant). The eggs (arrows)
in the ovaries have nearly matured (5.88 mm. long) ; U=uterus containing ootheca.
D.
Virgin female allatectomized at one day of age. After 52 days, cor- pora allata from two females 9 to 10 days of age were implanted. Oviposition occurred 28 to 35 days after implantation of corpora allata. The eggs (arrows) in the ovary are almost full grown (5.88 mm.) although an ootheca remains in the uterus (U).
E.
Ovary of a virgin female 43
days old. The oocytes are large an<{
degenerating (A-D= X2 ; E= X4).
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19623 Roth and Stay - Cockroach l99
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Table 5 - Effect on oocyte development of various implants into the abdomens of virgins of Byrsotria fumigata TYPE OF IMPLANT
INSERTED INTO
ABDOMEN
.GE (DAYS) OF
^EMALE AT
PERATION
Portion of an
ootheca of
By rsotria
Entire ootheca of
Pycnoscelus
Portion of an
ootheca of
Leucop haea
Controls
Wax "ootheca"
Untreated
LGE (DAYS)
VHEN OOCYTES
VERE MEASURED
OCYTES (MM.)
1EAN & S.E.
^One female had oocytes that were abnormally shaped and was not included in the measurements.
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19621 Roth and Stay - Cockroaches 201
Table 6 - Effect of severing the nerve cord on development of the oocytes, in Byrsotria females that were carrying oothecae DAYS AFTER
OVULATION NERVE
CORD WAS SEVERED
Virgin Females
o1
18
28
o1
21-27
Controls (sham
operated)
o1
Mated Females
12, 19
27-28
30-36
42-44
21-39
Controls (sham
operated)
12, 30,38
)AYS AFTER
)PERATION OOCYTE:
VERE MEASURED
lThe nerve cords of these females were severed prior to oviposition and therefore they may be considered to have had the cords cut when the female was ovipositing.
freed for the period of the experiment. The oocytes of these females measured o.78Ao.01 mm. In 3 females the remaining portion of the ootheca in the uterus continued to apply pressure on the ovipisitor and their oocytes measured 0.77k0.05 mm. As controls 6 females were sham operated, i.e. their oothecae were partly extruded and pushed back, without being cut off, into the uterus I I to I 3 days after ovula- tion. They all gave birth at 54 to 56 days of age and their oocytes measured o.74å±0.0 mm. These experiments indicate that relieving the pressure of the ootheca on the gonapophyses during pregnancy had no effect on oocyte development.
One mated female of the bisexual strain that had oviposited normal- ly failed to give birth in the usual ~eriod of time (53 days). It was
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202 Psyche [December
dissected after 62 days of pregnancy and the oocytes were 1.56 mm. long and contained yolk. The uterine eggs were degenerating and were undeveloped but the oocytes had developed although the egg case had been in the uterus. This failure of endocrine inhibition during "pregnancy" was also found in Blaberus and Byrsotria (see below).
Byrsotria fwnigata: The effect of various implants into the abdomi- nal cavities of virgins is shown in table 5. Portions of egg cases of Byrsotria and Leucophaea and entire oothecae of Pycnoscelus failed to inhibit the development of the oocytes in Byrsotria. Severance of the nerve cord in pregnant virgin and mated females resulted in resumption of oocyte development in some females (cf. figs. I ~ A and C) although an Gtheca was in the uterus (table 6). How- ever, the oocytes developed only in 7 of 24 virgins as compared to 15 of 20 mated individuals. All of the virgins that failed to develop oocytes had many degenerating oocytes that had not been laid during the initial ovulation which may account for the negative results in many of these females. Of the 7 virgin females that developed their oocytes after nerve cord severance, 5 had no old degenerating oocytes, one had one old oocyte and the last had several oocytes that had remained from the previous oviposition. In addition to the 24 virgin females that had been operated upon after ovulating (table 6), I I females had their nerve cords severed 7 to 24 days after emergence and 8 others were sham operated when 5 to 20 days old. These females failed to oviposit and were dissected 31 to 38 days after the operations. Of the nerve-cord-severed females 7 had matured degener- ating oocytes and 4 had small oocytes with some yolk but these had degenerated. Of the sham operated females 5 had mature degenerated oocytes, 2 had small degenerated oocytes and I had oocytes that failed to develop. The oocytes in females that had been operated on prior to oviposition were essentially similar to those found in unoperated virgin females.
Experiments were performed on several females to determine the effect of removing the ovipositors or relieving the pressure of the ootheca on the gonapophyses.
The ovipositors were cut off of g
virgin
females 6 to 26 days after oviposition.
The oocytes were
measured after the females had carried their oothecae for 75 to 84 days. In 8 females the oocytes measured 1.62å±0.0 mm. indicating no growth other than might be expected in unoperated females (1.53 å±o.o mm. at parturition). One female whose ovipositor was cut off 13 days after ovulation had oocytes 6.37 mm. after 82 days of pregnancy. The oothecae of 13 virgin females were partly extruded
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19 621 Roth and Stay - Cockroaches 20.3
manually, part of the egg cases were cut off and the remainder pushed back into the uterus in an attempt to free the pressure normally exert- ed on the ovipositor. In 6 successful operations the ovipositors were freed 9 to 12 days after ovulation, and at 73 to 75 days of "pregnancy" their oocytes were 1.47zk0.03 mm. Seven females in which the opera- tions (7 to 18 days after ovulation) did not free the ovipositors, had oocytes 1.49~0.05 mm. after carrying their oothecae for 71 to 76 days; one female that was unsuccessfully operated upon 8 days after ovulation had oocytes 3.77 mm. 64 days later. These experiments indicate that removing the ovipositor or releasing the pressure of the ootheca on the ovipositor during the gestation period does not influence the development of the oocytes. The two individuals in which the oikytes grew may be explained by the fact that inhibition of the cor- pora allata in some virgins of Byrsotria may break down during gesta- tion.
Blaberus craniifer: Parts of oothecae (about 5 mm. x 10 mm.) of B. craniifer were implanted into the abdomens of 9 virgin females less than I to 3 days old (one female had an entire ootheca implanted). Eight females dissected 15 to 30 days later had well developed oocytes 4.84k0.28 mm.; one female dissected 28 days after the implant showed no growth of oocytes (1.48 mm. long). The oocytes of unoperated virgins 15
to 30 days old were 5.10*0.05 mm. The
length of mature oocytes are about 6.25k0.07 mm. (N=3) ; the new basal kcyte at ovulation is I .1oko.03 mm. (N=5). Uterine eggs implanted into the abdomens of virgin females did not inhibit oocyte development in B. craniifer.
Six mated females had their nerve cords severed on the twenty- second to twenty-sixth days of pregnancy and were dissected 34 to 39 days later. Four of these females (operated on the twenty-fifth to twenty-sixth day of pregnancy) had oocytes 4.0gk0.84 mm., 34 to 38 days later (fig. 12 B) ; two females operated on the twenty-second and twenty-third days of pregnancy showed very little oocyte develop- ment ( 1.741k0.12 mm.), 34 and 39 days later (the oocytes at par- turition are I .56å±:0.0 mm. long ; N=6). Two virgin females of B. craniifer carried their oothecae for 93 and 107 days, which is longer than the normal gestation period (about 79 days) of mated females. When the undeveloped uterine eggs were extruded the oocytes measured 3.92 mm. and 3.68 mm. respectively (fig. 12C). Inhibition of the corpora allata in B. craniifer apparently can break down in the late stage of "pregnancy" in virgin females, as it does in Byrsotria and in Pycnoscelus. Blaberus giganteus: Eight pregnant females were taken from cul-
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204 Psyche [December
tures (histories unknown), their nerve cords were severed and their oocytes were measured on the day they gave birth or aborted their oothecae. Five females gave birth and 3 extruded oothecae containing well developed embryos in 19 to 33 days after the operations. In every female the oocytes grew, as a result of nerve severance, and measured 4.24k0.33 mm. At ovulation the mature oocyte is 5.86+0.04 mm. (N=I I)
and the new basal oijcyte is 0.97d10.01 mm. (N=6). Normally at parturition the oocytes are 1.67å±0.0 mm. long (N= 10). Gestation in this species lasts about 95 to 103 days. Nerve cord severance at least 33 days before parturition eliminated the inhibition of the corpora allata resulting from the presence of the egg case in the uterus.
Leucophaea nzaderae: The oothecae of 7 females were removed and part of the egg cases were implanted into the abdomens of the female donors. Five females which had their egg cases removed and im- planted 10 to 15 days after oviposition, ovulated 61 to 65 days later. This is about the time one would expect ovulation after removal of the ootheca (fig. I I ) . One female had oticytes 2.18 mm. long 65 days after an implant (made 10 days after ovulation). One female whose ootheca was removed and implanted 22 days after ovulation had oocytes 5.14 mm. long 41 days later. Four females whose oothecae were removed 14 to 40 days after ovulation and had a wax "otitheca" inserted into the uterus showed no yolk deposition in the oocytes ( I .05 k0.05 mm. ) 58 to 65 days later. The implantation of uterine eggs into the abdomens of females did not prevent the oocytes from maturing. The results with wax "oothe- cae" insertions indicate that the corpora allata may be inhibited by pressure of the ootheca in the uterus.
To determine whether there was a hormonal influence on oocyte development in Leucophaea, Engelmann ( I 957) removed the eggs from the uterus and implanted about one half of the ootheca into the abdominal cavity. He found that the eggs (in the ootheca) still affected the corpora allata when they were implanted into the abdo- men (as they did when in the uterus). To rule out any possible effect of a mechanical pressure on the abdomen, or the effect of other sub- stances resulting from decay of tissues (i.e. decaying implanted uterine eggs) he implanted paraffin blocks, muscle tissue, or agar blocks of about the size of half an ootheca after removal of the egg case. These implants did not inhibit the corpora allata and Engelmann concluded that the arrest of the corpora allata was not caused by mechanical pressure. However, it should be pointed out that pressure exerted by an implant in the abdominal cavity may be quite different from pres-
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19 621 Roth and Stay - Cockroaches 205
sure exerted in the uterus by the growing eggs (or by an implant into the uterus). In his more recent work ( 1960) Engelmann found that nerve cord severance did in fact result in renewed growth of the Gcytes in pregnant females and that nervous stimuli are ~rimarily responsible for inhibition of the corpora allata during pregnancy. However, he found a statistically significant delay of egg maturation after severance of the nerve cord, compared with animals from which egg cases were removed (35.2310.7 versus 39.1k1.4 days in animals operated on 29 to 37 days after ovulation; 64.72 1.9 vs. 73.4k 1.5 days å´' animals operated on o to I day after ovulation). He concluded that other factors play an important role in inhibiting the corpora allata during pregnancy. By injecting 0.1 ml. of clear supernatant fluid from homogenized uterine eggs every fifth day for 30 days, he inhibited the corpora allata of Leucophaea. However, the injection of muscle homogenate resulted in a similar inhibition and Engelmann suggested that a non-specific substance inhibited the corpora allata .during pregnancy.
Although Engelmann has shown a delay in ovulation in females that had nerve cords cut compared to females from which oothecae were removed and has demonstrated that extracts of uterine eggs and muscle tissue have an inhibitory effect on the corpora allata, he has not demonstrated that there is a substance normally produced by the uterine eggs which acts to inhibit the corpora allata. Our experiments do not corroborate Engelmann's finding that a substance from uterine eggs inhibits the corpora allata. We find that removing eggs from the uterus and implanting them into the abdomen (in Pycnoscelus, Byrso- tria, Blaberus craniifer and Leucophaea) removed inhibition of oocyte development, i.e. oocytes developed in the ovaries. We also find that cutting the nerve cord of pregnant females allows the oocytes to develop in the ovaries of Pycnoscelus, Byrsotria, Blaberus craniifer, and B. giganteus; we therefore conclude that the inhibition of the corpora allata during gestation, in these species at least, is dependent upon nervous stimuli resulting from the presence of the egg case in the uterus.
Engelmann (1960) concluded that in Leucophaea the inhibitory influence of the ootheca may act on the last abdominal ganglion either by nervous or chemical factors and that there was "no reason to believe that the presence of an egg case in the brood sac is mechanically recorded in the brain (Roth and Stay, 1959). The question is still undecided." Our conclusions in the 1959 paper were based on studies of Pycnoscelus swinam ensis and Blattella germanica. In the parthen- ogenetic strain of Pycnoscelus there is no inhibition of corpora allata
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206 Psyche [December
in virgin females prior to the first pregnancy, and severance of the nerve cord may affect the ability of the female to oviposit but has no influence on the rate of maturation of the oocytes. There is no inhibi- tory center in the last abdominal ganglion in this species before the first oviposition. The insertion of wax into the uterus, after removal of the ootheca, results in inhibition of the corpora allata, and indi- cates that a chemical substance from uterine eggs is not necessary for inhibition of corpora allata in Pycnoscelus. We interpret these results to mean that pressure from the stretched uterus regulates the secretion of the corpora allata. As suggested by Engelmann ( 1962) the inhibi- tory center may be caudal to the site of the operation and "the brain may act only as a way station for the transmission of nervous impulses." In Rhodnius prolixus the release of brain hormone was triggered by the distension of the insect's abdomen following a blood meal. Since cutting the nerve cord eliminated this effect, Wigglesworth ( I 934) inferred that the neurosecretory cells were influenced by nerve impul- ses arising in abdominal proprioceptors. The two stretch receptors found in each abdominal segment of Rhodnius adapt scarcely at all and will continue to discharge as long as the abdomen is stretched (Van der Klooi, 1961 ) . In all of the false ovoviviparous cockroaches the uterus becomes greatly distended as the eggs increase in size as a result of water uptake and growth (Roth and Willis, 1955). It is pos- sible that inhibition of the oocytes during pregnancy may be due to pressure on abdominal stretch receptors as in Rhodnius. However, it is also conceivable that there are mechanoreceptors in the uterus itself. The present evidence indicates that the ovipositor is not involved in transmitting the pressure stimulus from the o~theca in the uterus oi- genital chamber of Pycnoscelus and Byrsotria; similarly, the ovipositor in Blattella germanica is not involved in corpora allata inhibition while the female carries its egg case (Roth and Stay, 1962). In Blattella, which carries its ootheca externally, and in all cock- roaches that incubate their eggs internally, the ootheca swells during embryogenesis, particularly in the latter species (Roth and Willis, "1%) Igyja, 1958). We (Roth and Stay, 1959, 1961, 1962) have suggested that during pregnancy inhibition of the corpora allata is due to nervous stimuli resulting from pressure of the ootheca. The changing pressure stimulus resulting from the increase in size of the ootheca would tend to prevent or retard adaptation of the receptors involved so that the corpora allata are inhibited during the entire except in Diploptera and some Nauphoeta) gestation period. How- ever, in virgins of BlatteHa gt7r~nanica (Roth and Stay, 1962) Blaberus craniifer, Byrsotria fumigata, and Pycnoscelus s,urina?nensis
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19621 Roth and Stay - Cockroaches 207
(mated bisexual strain females whose uterine eggs do not develop) where the Gtheca does not increase markedly in size because the eggs remain undeveloped, inhibition of the corpora allata, resulting from the presence of the ootheca, ceases, and consequently the oocytes develop in spite of the presence of the egg case; it seems that because of the constant, more or less unchanging pressure stimulus resulting from an ootheca that is not increasing in size, pressure receptors (or the central nervous system) become adapted and nervous inhibition of the corpora data ceases.
ABSTRACT
The effect of mating on oocyte development and oviposition in PycnosceZus surina?nensis, Byrsotria fu?nigataJ Blaberus craniifer, Bla- h s gig<an/elus, Nauphoeta cinerea, and Leucophaea maderue, all cockroaches that incubate their eggs internally, was investigated. In Diploptera punctata, the majority of females require mating for maturation of the oocytes. In PycnosceZus mating is unnecessary for egg maturation. Between these two extremes are species which show varying degrees of dependence on external mating stimuli for over- coming inhibition or for stimulating corpora allata. Various species also show different degrees of dependence on mating for normal form- ation and retraction of the ootheca into the uterus. The extent to which cockroaches depend upon food intake for stimu- lation of the corpora allata also varies. The species may be arranged in a series showing complete dependence to complete independence upon food for oocyte development.
Experiments to determine the nature of inhibition of the corpora allata during pregnancy indicate that inhibition is due to nervous stimuli resulting from pressure of the growing eggs in the uterus. BARTH, R. H. JR.
1961. Hormonal control of sex attractant production in the Cuban cockroach. Science 13 3 :1598-9.
1962.
The endocrine control of mating behavior in the cockroach Byrso- tria fumigata (Gubrin). Gen. and Comp. Endocrinology 2 53-69. ENGELMANN, F.
1957. Die Steuerung der Ovarfunktion bei der ovoviviparen Schabe Leucophaea maderae (Fabr.) Jour. Ins. Physiol. 1 257-78, 1957a. Bau und Funktion des weiblichen Geschlechtsapparates bei der ovoviviparen Schabe Leucophaea maderae (Fabr.) und einige Beobachtungen uber die Entwicklung. Biol. Zentr. 769'22-40. 1959. The control of reproduction in Diploptera punctata (Blattaria). Biol. Bull. 116 :406-19.
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Psyche [December
1960. Mechanisms controlling reproduction in two viviparous cock- roaches (Blattaria). Ann. New York Acad. Sci. 89 516-36. 1960a. Hormonal control of mating behavior in an insect. Experientia 16 :69-70.
1962. Further experiments on the regulation of the sexual cycle in females of Leucophaea maderae (Blattaria) . Gen. and Comp. Endocrinology 2:183-92.
JOHANSSON, A. S.
1955.
The relationship between corpora allata and reproductive organs in starved female Leucophaea maderae (Blattaria). Biol. Bull. 10 8 :40-4.
ROTH, L. M., AND BARBARA STAY
1959. Control of oocyte development in cockroaches. Science 130 271-2. 1961. Oocyte development in Diploptera punctata (Eschscholtz) (Blat- taria). Journ. Ins. Physiol. 7 :186-202. 1962. Oocyte development in Blattella gcrmanica (Linn.) and Blattella vaqa Hebard (Blattaria). Ann. Ent. Soc. Amer. 5 5 :633-42. ROTH, L. M., AND E. R. WILLIS
1954. The reproduction of cockroaches. Smithson. Misc. Coll. 122 :1-49. 1955. Water content of cockroach eggs during embryogenesis in relation to oviposition behavior. Jour. Exp. 2001. 128:489-510. 1955a. Intra-uterine nutrition of the "beetle-roach" Diploptera dytiscoides (Serv.) during embryogenesis, with notes on its biology in the laboratory (Blattaria : Diplopteridae) . Psyche 26 :55-68. 1956. Parthenogenesis in cockroaches. Ann. Ent. Soc. Amer. 49 :l95-204. 1958. An analysis of oviparity and viviparity in the Blattaria. Trans.
Amer. Ent. Soc. 83 :221-38.
1961. A study of bisexual and parthenogenetic strains of Pycnoscelus suhzamensis (Blattaria : Epilamprinae). Ann. Ent. Soc. Amer. 54 ~12-25.
SCHARRER, B.
1946.
The relationship between corpora allata and reproductive organs in adult Leucophaea maderae (Orthoptera) . Endocrinology 3 8 :46- 55-
VAN DER KLOOT, W. G.
1961. Insect metamorphosis and its endocrine control. Amer. 2001. 1: 3-9.
WIGGLESWORTH, V. B.
1934. The physiology of ecdysis in Rhodnius prolixus (Hemiptera). 11. Factors controlling moulting and 'metamorphosis'. Quart. J our. Micr. Sci. 77 :191-222.
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Volume 69 table of contents