Ruth Marshall.
A New Species of Water Mite from Thermal Springs.
Psyche 35(2):92-97, 1928.

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92 Psyche [June
A NEW SPECIES OF WATER MITE FROM THERMAL SPRINGS
Rockford College, Rockford, Illinois.
During the summer of 1927, Professor Charles T. Brues, of the Bussey Institution for Research in Applied Biology, found several water mites in collections made in thermal springs of Nevada in the course of his investigations upon the life in such habitats. He kindly sent these specimens to the writer for further investigation.
A search in the literature of the Hydracarina reveals very few records of their occurrence in thermal waters. Dr. Karl Viets, of Bremen, who has studied the group extensively, con- firms this statement in a private communication to the author. The earliest account appears to be that of Plateau (2) who records the finding of Hydrachna cruenta in springs of a tem- perature of 46OC., at Luxeuil, France, in the course of experi- ments on the determination of the thermal death point of several fresh water arthropods.
This record is quoted by Brues (1) in
recent papers on life in thermal waters. The identity of this species seems to be in some doubt, but it is probably a widely distributed European form.
Two other records have appeared during the past year. Uchida (4) has described a new species, Eylais thermalis from a single specimen found in a spring of temperature 42'C., near Taihoku, in the island of Formosa, Dr. Iwan Sokolow (3), ex- amining material collected near Lake Baikal, Siberia, in springs of temperature 45OC., found three individuals which he has des- cribed very fully and named Thermacarus thermobius, a new genus and new species. He has also erected for them a new family, Thermacaridce. The American material is a new species belonging to this genus, to which the name Thermacarus neva- densis has been given.
Pu&e 35:92-97 ( 1928). hup ttpsychu einclub orgt15/35-OS12 html



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A New Species of Water Mite
Thermacarus nevadensis sp. nov.
PI. Ill, fig. 1-9.
The body is obovate, slightly widest in the region of the third pair of legs. Females measure 2.50-3.00 mm. ; the males are slightly shorter and slimmer, the smallest, a young adult, being but 1.90 mm. It is thus seen to be smaller than 2'. iher- mobius. The color of the specimens, preserved in alcohol, was dull olive green with some traces of red. Two individuals showed white irregular branching streaks on the dorsal side. The body
is low, somewhat arched; dorsally and ventrally the integument is heavily chitinized to form two shields, the dorsal somewhat the smaller, united by a thinner layer.
Heavy ridges on the
dorsal side enclose two irregularly oval areas, one inside of the other (fig. 1). The double eyes of either side are outside of these ridges. The median sense organ is just within the larger area and is inconspicuous. The heavy integument shows in alco- holic medium a transparent, somewhat irregular layer, below which are low elevations irregularly scattered about on a basal layer; the latter shows rounded pores in groups of some ten to twenty enclosed in an irregularly polygonal meshwork (fig. 7). The conspicuous feature of the ventral side is the great development of the plates (figs. 2, 8, 9), the epimera closely resembling those of the related species. The first pair of plates, the largest, are fused not only ventrally but also dorsally so as ' to form a shallow cavity, reaching to the body margin or slightly projecting beyond it in the male, which encloses the small capi- tulum and the palpi. The fused epimera bear many hairs. The
three remaining epimeral pairs are somewhat triangular, except that the fourth in the male is rectangular. Posterior to the epimera in the new species is another plate, a large median one, heavily chitinized and bearing the so-called anal spot, differing in size and shape in the two sexes and in contour in individuals of differing ages, and completing the closure of the genital areas. The genital area in the male (fig. 2) is nearly circular, past the center of the body and enclosed by the fourth epimera and the medial posterior plate. Its valves are heavily chitinized



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94 Psyche [June
and support several long fine hairs.
The female genital area
is oval (fig. 8), situated a little above the center of the body and enclosed by the inner ends of the epimera as well as by the posterior plate. The valves of the opening are also heavily chi- tinized and bear hairs; they show more conspicuously than in the male a division into an anterior inner part and a posterior outer part, the latter showing numerous circular acetabula. One female (fig. 9), was found with the large ovipositor extended through the genital slit. This organ is a delicate, light colored structure within which could be seen the outlines of the nearly circular eggs.
The palpi (fig. 4, 5, 8) are very small and appeared always within the enclosure formed by the united first pair of epimera. They are flattened and are borne on the sides of a slender capi- tulum near the top. A conspicuous feature is the presence of two long curved doubly bifid bristles on the distal end of the second segment.
The legs are short, stout, increasing in length from first to fourth. The first three pairs are much like those of the related species and show the same partial union of the first two segments. They bear many heavy bristles, but these are somewhat longer than in the Asiatic form. All end in large double claws, orange red and beset with teeth on the curved side. The fourth leg in the female (fig. 6) is similar to the third but longer; in the male it is considerably modified (fig. 3) and doubtless used as a copulatory organ. The last three segments here are flattened, the fourth showing a plate-like expansion on the inner side; the last two segments are thickly beset with stiff hairs, the fifth being the longest and the sixth not much shorter, but broader with the claws lacking the teeth.
The types were secured in two collections from Nevada, a total of nine individuals. .
Three males and four females were found in water of tem- perature of 43OC., fifteen miles north of Deeth; and a young male and a female in temperature 42.5'-45 OC., in the Valley Hot Springs at Minden.
The new species is seen to be closely related to the Asiatic



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19281 A New Species of Water Mite 95
species but differs from it in several well marked characteristics. Specific characters of greatest importance in T. nevadensis appear to be the development of the heavy plat,e posterior to the epimera, the characters of the palpi with the large curved bifid bristles on the second segment; and the character of the fourth leg of the male with its last three segments elongated as well as flattened and richly supplied with st,iff hairs.
1. Brues, C. T. 1924. Observations on Animal Life in the Thermal Waters of Yellowstone Park,
with Consideration of the Thermal En-
vironment. Proc. American Acad. Arts
and Sci., vol. 59, pt. 15:371-437.
2. Plateau, F. 1870. Recherches physico-chimiques sur les Articul6s aquatiques. Pt. 1, M6m.
Acad. Roy. Sci. Belgique, vol. 36,68 pp. 3. Sokolow, I. 1927. Therrnacarus therrnobius, n. g., m. sp., eine Hydracarine aus heisser Quelle.
2001. Anz., LXXIII: 11-20.
4. Uchida, Tohru.1927. Notes on a new Water Mite from a Hot Spring. An. Zool. Japonenses, Vol. 11,
2: 111-114.




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Psyche
Pig. 1, dorsal view, male
Fig. 2, ventral plates, male
Fig. 3, fourth leg of male
Fig. 4, palpus, right, inner side (first segment lacking) Fig. 5, capitulum and palpus
Fig. 6, end of fourth leg, female
Fig. 7, detail of integument
Fig. 8, ventral plates, female
Fig. 9, ovipositor extended




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