Thermacarus nevadensis (Nevada Water Mite)

[sebbe67]

Thermacarus nevadensis, this animals were endemic to Nevada, USA it become extinct somewhere in the 1930.

[Peter]

Moved this to "Other Recently Extinct Animals" as it is not a mollusc, but belongs to the phylum of Arthropoda.

[sebbe67]

Thermacarus nevadensis sp. nov.
P1. III, 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 ram. It is thus seen to be smaller than T. thermobius.
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 alcoholic
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 capitulum
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
94 Psyche [June
and support severM long fine hairs. The femMe genitM 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 vlves of the opening are Mso heavily chitinized
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 acetabul. One
female (fig. 9), was found with the lrge 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 ppeared always
within the enclosure formed by the united first pir of epimer.
They are flattened and are borne on the sides of slender cpitulum
near the top. A conspicuous feature is the presence of
two long curved doubly bifid bristles on the distl end of the
second segment.
The legs are short, stout, increasing in length from first, to
fourth. The first three pirs are much like those of the related
species and show the sme prtial union of the first two segments.
They bear many heavy bristles, but these re somewhat longer
thn in the Asiatic form. All end in large double clws, 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 mle
it is considerably modified (fig. 3) and doubtless used as
copulatory organ. The last three segments here are flattened,
the fourth showing plate-like expansion on the inner side; the
last two segments are thickly beset with stiff hirs, the fifth
being the longest and the sixth not much shorter, but broader
with the clws lacking the teeth.
The types were secured in two collections from Nevada,
totM of nine individuals.
Three mMes and four females were found in water of ternperature
of 43C., fifteen miles north of Deeth; and young
mMe and a female in temperature 42.5-45C., in the Vlley
Hot Springs at Minden.
The new species is seen to be closely related to the Asiatic
1928 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 plate 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 stiff hairs.

Source: A NEW SPECIES OF WATER MITE FROM THERMAL
SPRINGS

[Deleted]

Thermacarus nevadensis



some parts of the body

from:

psyche.entclub.org/pdf/35/35-092.pdf

[Melanie]

Via Shoutbox by

user Rosamond

Thermacarus nevadensis is alive and well. I just pulled a specimen from a bioassessment sample taken at Reynolds springs, Railroad Valley, Nv. Dave Herbst also has found them in Travertine sp, Death Valley Ca, as well as a new sp.

[Melanie]

I must say I have a problem with the claim that this species is indeed rediscovered because there is absolutely no evidence and no press release about that.

[surroundx]

Apr 24, 2005 16:44:31 GMT sebbe67 said:

Thermacarus nevadensis, this animals were endemic to Nevada, USA it become extinct somewhere in the 1930.

Oct 19, 2013 11:24:09 GMT Melanie said:

I must say I have a problem with the claim that this species is indeed rediscovered because there is absolutely no evidence and no press release about that.

If this species is now extinct, or thought to be extinct, it's presumed extinction must have been some time after 11 or 12 July 1972 because according to (Collins et al. 1976:1223):

"Two weeks after the census [of 11 and 12 July 1972], 124 adult Thermacarus nevadensis were taken on the regrowing mat."

Although they also say (Ibid., p.1223):

"After these collections only one Thermacarus was seen in the spring."

But (Nyquist, 1965) had already reported a range extension for this species so it may have survived elsewhere if the collection of 1 individual from the spring post-1972 reported by (Collins et al. 1976) indicates local extinction (we don't know anything about their collecting methods so it is hard to determine how likely it is that they're only finding one specimen post-July 1972 indicates local extinction). There are also other citations which would seem to indicate its survival at other places post-1930 (Brues, 1932 and others) and I can find no mention in the literature of this species being even at risk of extinction. So perhaps it is the case that this species was never considered at risk of extinction in the first place, which would explain the lack of any press release mentioned by Melanie.

References

Brues, Charles T. (1932). Further Studies on the Fauna of North American Hot Springs. Proceedings of the American Academy of Arts and Sciences 67(7): 185-303.

Nicholas C. Collins, Rodger Mitchell and Richard G. Wiegert. (1976). Functional Analysis of a Thermal Spring Ecosystem, with an Evaluation of the Role of Consumers. Ecology 57(6): 1221-1232. [Abstract]

Nyquist, D. (1965). An extension of the range of Thermacarus nevadensis Marshall. Proceedings of the Utah Academy of Sciences, Arts, and Letters 42(2): 177. [published in 1966?]