Atractides from Britanny – identification in progress

By
yann
Posted in: 29 Finistère - Saint-Thegonnec - Mouth of the stream of Kerescars, Atractides, Water mites

fig 10 Atractides dorsal

Caught the 4th of July of 2011 in the mouth of the stream of Kerescars in Brittany.

My observations.

  • Length : 0.9 mm
  • Width : 0.76 mm
  • Colour : a mixed shade of brown, yellow and white.  The white lines (excretory organ) are also covering the posterior part of the ventral surface.
  • Eyes brown.
  • Acetabulae grouped by 3 with a rather large yellow area in between (fig 50).
  • A clear zone between the eyes and the mouth is almost rectangular, a clear yellow, with 2 dark bristles (fig 40).
  • 2 or 3 long setae at the end of the 4th segment of the first pair of leg (fig 30 & fig 60).
  • Fifth segment of the first pair of leg much thinner than the other segment of the same leg.
  • Coxae : hard to judge with my set of pictures.

Log of my process of identification.

  • This mite share some feature with Hygrobates longipalpis. But the disposition of the acetabulae and the shape of the end of the first pair of legs doesn’t match.
  • In Piersig 1900 (plate 18 – fig 45 – page 536) some similarity  with Atractides spinipes. Matching : disposition of the acetabulae, shape of the first leg, colour scheme, disposition of the eyes, frontal setae…
  • Piersig 1900 (plate 46 – fig 144 – page 591) Atractides gibberipalpis. Shape of the first leg.
  • Piersig 1900 (plate 46 – fig 182 – page 591) Atractides loricatus. Disposition of the acetabulae, shape of the palpi, shape of the first leg.
  • In 2011 there are 297 known species of Atractides. 123 species in Europe. (Pešić and  Smit 2011). The identification task may be quite difficult.
  • There is an interesting publication by Gerecke in 2003 about the european Atractides. It seam that I have to get this paper to be able to identify my Breton water mite.

References

  • Gerecke R. (2003) Water mites of the genus Atractides Koch, 1837 (Acari: Parasitengona: Hygrobatidae) in the western Palaearctic region: A revision. Zoological Journal of the Linnean Society 138:141-378.
  • Pešić, W. and  Smit, H. (2011). A new species of Atractides Koch, 1837 (Acari, Hydrachnidia, Hygrobatidae) from Ethiopia, with a discussion on the biodiversity of the genus Atractides in the Afrotropical region. Zookeys. 2011; (86): 1–10. Article in open access.
  • Piersig,R. (1900). Deutschlands Hydrachniden. Zoologica. Verlag von Erwin Nägele in Stuttgart.

Other pictures.

fig 20 ventral

fig 30 frontal lateral

fig 40 eyes and frontal setae

fig 50 acatabulae

fig 60 palpi and last segment of first leg

fig 70 ventral lateral

fig 80 third and fourth coxae plates

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