Echiniscus

Gąsiorek, Piotr, 2023, Eventually tested: Phylogenetic position of “ Testechiniscus ” meridionalis (Murray, 1906) (Heterotardigrada) revealed, Zoologischer Anzeiger 304, pp. 49-60 : 58

4.3. Re-defining Echiniscus

Currently, the definition says “Echiniscids with red eyes composed of pigment granules. Rigid buccal tube lacking stylet supports or with fine, fibrillar stylet supports. Two pairs of segmental plates. Two or three median plates, sometimes transversally subdivided. Incisions(notches) on caudal (terminal) plate. No pseudosegmental plates. Ventral subcephalic and/or genital plates may be present.” ( Gąsiorek et al., 2017). The necessary modification obviously concerns the last sentence, which is rephrased as “Ventral plates may be present, usually only in the form of subcephalic and/or genital plates.”. The affinity of E. becki ( Schuster and Grigarick, 1966) remains problematic and thus, consequently, I left its classification unchanged. However, it is clear that this species does not belong in Echiniscus because of the presence of black crystalline eyes ( Fig. 9B ), which, together with the dorsal plate sculpturing dominated by polygonal endocuticular pillars, make it most similar to Diploechiniscus . Ultimately, E. becki does not exhibit dorsolateral spicules and is comparatively larger (adults 290–420 μm in length) than Diploechiniscus oihonnae (adults <275 μm in length). The last record of this species, endemic to the Western Nearctic, came from Mexico (Nú˜ nez et al., 2021), yet it is clearly erroneous as the reported individuals had reticulum in their dorsal plates, absent in the paratypes of E. becki ( Fig. 9A ). Therefore, re-sampling the Californian localities is necessary to obtain DNA barcodes and clarify where this species should be classified.

Figures

Fig. 9. Cephalic body portion of Echiniscus becki (PCM, paratype, female): A – dorsal view, B – ventral view (arrowheads indicate black crystalline eyes; large subcephalic plates visible as dark grey, broad belts bent in a boomerang-like shape). Scale bars = 10 μm.