Elizabetwh Aldorf.
Grooming through the reproductive cycle in male Sinella coeca (Collembola: Entomobryidae).
Psyche 82(3-4):359-365, 1975.

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GROOMING THROUGH THE REPRODUCTIVE
CYCLE IN MALE SINELLA COECA
. (COLLEMBOLA: ENTOMOBRYIDAE)*
BY ELIZABETH WALDORF
Department of Zoology and Physiology
Louisiana State University
Baton Rouge, Louisiana 70893
Pheromones function in several roles important in insect repro- duction: location of associate, species recognition, sex recognition, and as a~hrodisiacs. The receptors that detect most sex phero- mones are located on the antennae and mouth parts. Grooming behaviors free these sensory surfaces of foreign materials perrniting their optimal functioning.
Collembola are commonly very abundant in leaf litter and soil ranging up to 200,000 per m2 (Hale, 1967). They contribute by their food processing and locomotion to soil genesis and the main- tenance of soil fertility.
Their abundance is due not to a large
diversity of species, but to a high reproductive potential (Kuhnelt, 1961).
Reproduction utilizes indirect sperm transfer via stalked sperrn- atophores. In Sinella curvifeta Brook (Family Entomobryidae) spermatophore deposition by males is stimulated by a female sex pheromone ( Waldorf, I 9743). Under ideal conditions, Sinella curviseta females can deposit an average of 45 eggs every 8 days for 3 months (Waldorf, 1971 ; Niijima, 1973). Both sexes in this species release gametes during specific intervals that alternate with nonreproductive periods (Waldorf, 197 I ) . Males and females molt twice between successive reproductive intervals. Although reproduction has not been described in Sinella caeca (Schott), preliminary work suggested that the frequency of cleaning might vary with the reproductive condition of the individual (Wal- dorf, 1974b). These data demonstrate a difference between the sexes in the frequency of grooming, with males grooming more often. In addition, the frequency of grooming in females depends on the reproductive condition of the female. This study examined the frequency of grooming in Sinella coma males in a sequence of reproductive conditions. Since females with *Manuscript 'received by the editor January 16, 1976 359




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360 Psyche [September-December
eggs groom more often than other females (Waldorf, 1974b), I expected males depositing spermatophores to exhibit a higher rate of grooming.
Mass cultures of Sinella coeca were maintained as previously described (Waldorf, 1971 ) . Animals were held at room tempera- ture (25-26OC) in constant light. Brewer's yeast was provided as 'food and replaced as the supply became contaminated with fungal growth.
Ten pharate males were isolated in individual plastic-capped glass vials. The vials with an inner diameter of 22.0 mm contained a moist plaster of paris-charcoal substrate and food. Each male was observed for five minutes every 12 hours for 10 days. With the observer wearing a fiber mask to reduce disturbance of'the animals, observations were begun 12 hours after isolation. Records were made of number of bouts of antenna1 grooming, total number of bouts of grooming and total seconds grooming. For the latter an electric second counter was activated by a depression switch. In addition, exuvia were removed and their presence recorded, and observations of spermatophore deposition behavior were noted. Table I. The lengths of reproductive and nonreproductive instars in male Sinella coeca in days at 25-26OC. Reproductive Nonreproductive
instal- instar
Instar length
SD
No. of males
Spermatophore deposition behaviors occur in Sinella coeca only in alternate instars. The lengths of the two types of instar (Table I) differ significantly (t = 6.62, df 17 ; P < .005). The reproductive instars average 5.4 days, one and % times the length of the non- reproductive ones.
The percentages of the males exhibiting spermatophore deposition behavior through the reproductive instar appear in figure I. The maximum occurred early in the instar with all males depositing spermatophores spontaneously 24-36 hours after ecdysis. There is a



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19751 Waldorf - sinella coeca 361
gradual decline until 6 hours ~rior to the next ecdysis when no males exhibited this behavior.
Neither the number of bouts of cleaning nor the lengths of these differed in reproductive as compared with nonreproductive males. The averages, considering all grooming, are presented in Table 2. Similarly, there are no differences in antennal grooming as a func- tion of reproductive condition.
The average frequencies of grooming through the instars are illustrated in figure 2. The patterns in reproductive and nonrepro- ductive males are essentially the same. Both groom most frequently 12-18 hours after ecdysis. Thereafter a lower rate is more or less constant until 70-75% of the instar has elapsed. This declines 'to near zero before ecdysis. Of the 11 pharate males observed in previous experiments, only one performed one antennal cleaning. Table 2. The average number of bouts of grooming in 5 min. and their average duration in male Sinella coeca in the reproductive and nonreproductive instars. No. of bouts
Length of bouts
per animal (in sec)
Reproductive instar I .3 10
.5 18
25.93 98 15.86
Nonreproductive instar
I .3 10 .441
23.43 49 10.48
The pattern of alternate reproductive and nonreproductive instars observed in Sinella coeca characterizes both sexes of Sinella curviseta (Waldorf, 1971) and some members of the genera Orchesella, Tomocerus and Isotoma ( Poggendorf, 1956 ; Mayer, I 957 ; Joosse and Veltkamp, 1970). Similarly, reproductive instars are longer in males of S. curviseta (Waldorf, 1971) and OrcheseZZa cincta L. ( Poggendorf, I 956) than nonreproductive ones. Although not enough data are available to draw a conclusion, this pattern might apply generally within the family Entomobryidae. The experimental observations of isolated males provided estimates of the frequency olf spontaneous grooming. The data indicate that
the rate of spontaneous grooming does not vary between types of instar but does vary within instars.
Fluctuations in response to female (or male) associates might be superimposed on the basic pattern (fig. 2). An example of the effect



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Psyche
[September-December
Figure 1. The percentages of males depositing spermatophores through the reproductive instars. Ages are given in hours relative to ecdyses (e) at the onset and conclusion of the instar. of association has been reported in Sminthurides aquaticus Bourlet (Mayer, 1957). Males of this springtail clasp the antennae of females and are carried about by the females. Such males groom more than unattached males.
The previous finding (Waldorf, 1974b) that Sinella coeca males groom more frequently than females is possibly explained by the positive correlation reported by Jander (1966). She found higher rates of grooming in animals that exhibited more locomotor activity. S. coeca males are more active than females. This correlation receives further support from comparison with SineZZa curviseta males. S. coeca males groomed their antennae about 1.8 times in 5 min. This contrasts with .4 antenna1 cleanings ob- served on the average in five min (at the same temperature) in the less active 8. curviseta males (n = 10; SD = .70). My earlier data (1974b) on variation in grooming in S. coeca females, although less precise, was similar to the pattern in males shown in figure 2. In that experiment the category termed newly ecdysed females (ecdysis (e) to e + 22 hours) exhibited moderate frequency of grooming; 'females with eggs (e + 24 to e + 44 hours) exhibited the highest frequency of cleaning; and, other females > e + 24 hours in nonreproductive instars and >e + 44 hours in reproductive ones, assuming these occur) exhibited the lowest. Since these females were observed at 23OC (in contrast to 25-26OC for males in the present experiment), the hours cannot 'be compared exactly.




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Wdldorf - Sinella coeca
HOURS IN NONREPRODUCTIVE INSTAR (-1
et6 et18 midpt. e-18 e-6 e
HOURS IN REPRODUCTIVE INSTAR (-1
Figure 2. Average number of bouts of grooming behavior in 5 min through the reproductive and nonreproductive instars. Ages are given in hours relative to ecdyses (e) at the onset and conclusion of the instars. Lepidocyrtus cyaneus Tullberg cleans its antennae twice in five minutes and its legs an average of I .3 times (Pedigo, 1967). These compare with 1.8 times for antennae and a smaller value for leg grooming in male Sinella coeca. These rates are remarkably similar, perhaps indicating equal rates of locomotor activity in the two species. However, ilf Lepidocyrtus males are more active than females, those frequencies might be averages of the higher rate of grooming in males with the lower one in females. The location in instars of the maximum grooming rate is of interest. In S. curviseta, females pick-up and utilize sperm only during about the first 20 hocurs of the reproductive instars (Waldorf, I 97 I ) . During this interval females release a volatile sex pheromone that increases male spermatophore deposition ( Waldorf, I 974a). Further Joosse ( I 975 ) reports that certain events synchronize molt- ing in natural populations of species of Entomobryidae. Conse- quently, if Sinella coeca females are similar to S. curviseta ones, the maximum spontaneous grooming in males might often coincide with the presence of the female sex pheromone.



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364 Psyche [September-December
In Orchesella cincta males, spermatophore deposition occurs typi- cally only in the first half of the reproductive instar (Joosse, Brug- man and Veld, I 973 ) . The maximum number of males of Sinella coeca exhibit spontaneous spermatophore deposition in the first half of the instar. If reproduction in S. coeca females resembles that in S. curviseta and synchronization of molting occurs, 8. coeca females. probably have access to an abundance of spermatophores. I gratefully .acknowledge the support of a Summer Faculty Re- search Grant from the LSU Council on Research. HALE, W. G.
1967. Collembola. Chap. 12 in Soil Biology. A. Burges and F. Raw (eds.) , pp. 397-411.
JANDER, URSULA
1966. Untersuchungen zur Stammesgeschichte von Putzbewegungen von Tracheaten. Z. Tierphysiologie 23 : 799-844. JOOSSE, E. N. G.
1975. Feeding activity and availability of food in Collembola. Progress in Soil Zoology. Proc. 5th International Colloquim on Soil Zoology. Prague 1973. pp. 315-324.
JOOSSE, E. N. G., F. A. BRUGMAN AND C. J. VELD 1973. The effects of constant and fluctuating temperatures on the pro- duction of spermatophores and eggs in populations of Orchesella cbtcta (Linne), (Collembola, Entomobryidae) . Netherlands J. of ZOO\. 23 : 488-502.
JOOSSE, E. N. G. AND E. VELTKAMP
1970. Some aspects of growth, moulting and reproduction in five species of surface dwelling Collembola. Netherlands J. of 2001. 20: 315- 328.
KUHNELT, W.
1961. Soil Biology. Translated by Norman Walker. Faber & Faber, London, 397 p.
MAYER, H.
1957. Zur Biologic und Ethologie einheimischer Collembolen. 2001. Jahr. Systematik Okol. u. Geograph. Tiere, 85: 501-570. NII JIMA, KEIKO
1973. Experimental studies on the life history, fecundity and growth of Sinella curwiseta ( Apterygota, Collembola) . Pedobiologia 13 : 18 6-204.
PEDIW, LARRY P.
1967. Selected life history phenomena of Lepidocyrtus cyaneus f. cine- reus Folsom with reference to grooming and the role of the collophore (Collembola: Entomobryidae). Entomol. News 78 : 263-267.




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19751 Wa1dw-f -- sinella coeca
POGGENDORF, D.
1956. Uber rhythmische sexuelle Aktivitat und ihre Beziehungen zu Hautung und Haarbildung bei arthropleonen Collembolen (Spring- schwanze). Naturwissenschaften. Berlin 43 : 45. WALDORF, E. S.
1971. The reproductive biology of Sinella curviseta (Collembola: Entomobryidae) in laboratory culture. Rev. Ecol. Biol. Sol 8 (3) : 451-463.
1974a. Sex pheromone in the springtail Sinella curviseta. Environ. Entomol. 3 : 916-918.
1974b. Variations in cleaning between the sexes of Sinella coeca (Collembola : Entomobryidae) . Psyche 8 1 : 254-257.



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