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At left: the underside of the watermite I have identified to be Tiphys ornatus.
The cf. indicates my uncertainty on this. The size is correct: other Tiphys
species are smaller. The palps make me doubtful: more abut that lower on this page.
The genital plates of this watermite bear some resemblance with those of Pionopsis lutescens, but that species has the second and third
acetabula in a more side by side position, and so the genital plates form a square angle,
not the sickle shape we find here. Tuzovsky (2011) made some drawings of the genital plates
of T. ornatus with the acetabula in various positions, his last example shows the
second and third in a position that is almost the same as mentioned on P. lutescens,
so this might cause confusion when identifying some specimen of T. ornatus.
For the rest, the ventral side looks very similar to that of most Piona species, as Tiphys is closely related to these. It is probably difficult to classify the Tiphys genus, with the six acetabula and the males that differ from most Piona males. Piersig (1897) describes the species as Piona ornatus. Compare the Piona cf. nodata below, that I thought to be a smaller Tiphys specimen, because it was in the same catch.
Left and below left: mark the long projections below the forth epimers: Pionopsis lutescens has these too. The length of the medial border of the forth epimers is about twice that of the third.
The somewhat magnified picture at left shows the genital bay, some of the hairfollicles beside the acetubala are vaguely visible. The extra border, visible around one of the forth epimers, was also mentioned by Piersig (1897).
Below here: the palps, from under PIV seemed to have a clubbed outline, but in lateral view it appears rather thin. That might establish the species name.
The three pictures below "zoom in" on a small dorsal shield on the back of the mite. The left one is a (not very good) stacked picture, and the right one shows the dorsal shield on the left side of the mite. An identical shield could be on the right side, but that part isn't visible very well. Tuzovsky (2011) has a drawing of these two shields, and that drawing also shows two smaller shields close behind the former ones. These smaller shields are not visible on the picture here.
About the name:
Etymology: Tiphys: read below here, ornatus: decorated, probably referring to the striking orange-yellow spot.
The different names for this watermite in older literature make a good example of the
troublesome taxonomy of watermites in general.
The german entomologist Carl Ludwig Koch gave the genus in which he placed this mite the
name Tiphys in 1836. But in 1842 he changed the name to Acercus, because he
thought the name Tiphys was already given to a genus of crustaceans (Oudemans, 1897).
”As this is not true -” Oudemans (1897) wrote, ”the genus of Crustacea is called
Typhis - the name Tiphys Koch 1836 must be rehabilitated, and
Acercus Koch, 1842, is only a synonym to Tiphys Koch, 1836.”
Oudemans is referring to the rule that the oldest valid name should be used, and indeed the
name Tiphys is restored. Viets (1936) wrote in a footnote under his Acercus ornatus
the same story (Oudemans and he were acquainted). He supposes that Tiphys was a write
failure, and a valid name, because it's unique and also suggests that Acercus
should be changed to Tiphys. I have my doubts about the ”write failure ”idea: Tiphys
was the name of the helmsman of the Argo, the famous mythical ship of the Argonauts, and so
it is a fine name for a watermite genus.
Piersig (1897) describes this watermite as Piona ornatus. He used the name
Piona for what is now the genus Tiphys, the name Acercus for a number
of watermites that are now called Forelia species and Curvipes for what are at
present a number of Piona species, a clear example of the difficulties with watermite
names.
REFERENCE LIST
Tuzovsky, P.V. (2011) Water mites of the genus Tiphys Koch, 1836 (Acariformes: Pionidae)
in Russia. Acarina 19 (2): 113 - 212. Institute of Biology of Inland Waters, Russian
Academy of Sciences, Borok, Yaroslavl Province, 152742 Russia
Retrieved 2012 from:
http://insects.ummz.lsa.umich.edu/ACARINA/PDFS/2011_2/Tuzovsky2011.pdf
Oudemans, A.C. (1897) List of Dutch Acari. Tijdschrift voor Entomologie 40, 1897 De
Nederlandsche Entomologische Vereeniging (p. 248).
Retrieved 2012 from:
http://ia600302.us.archive.org/11/items/tijdschriftvoore401897nede/tijdschriftvoore401897nede.pdf
Read 2012, online version page 248:
http://www23.us.archive.org/stream/tijdschriftvoor42veregoog#page/n338/mode/2up
Read 2012, another online version from:
http://www.biodiversitylibrary.org/item/40960#page/342/mode/1up
See also the Watermite REFERENCE LIST.
