Stygobromus anastasiae, Sidorov, Dmitry A., Holsinger, John R. & Takhteev, Vadim V., 2010

Sidorov, Dmitry A., Holsinger, John R. & Takhteev, Vadim V., 2010, Two new species of the subterranean amphipod genus Stygobromus (Amphipoda: Crangonyctidae) from Siberia, with new data on Stygobromus pusillus (Martynov) and remarks on morphology and biogeographic relationships, Zootaxa 2478, pp. 41-58 : 55

Remarks on Stygobromus morphology

Morphological investigation of the Siberian Stygobromus with assistance of SEM revealed additional characters that appear to be taxonomically significant. They include: (1) a naked vestigial segment on the tip of antennae 1 and 2 approximately 10 mkm long ( Figs 68, 69 ); and (2) a “squamiferous membrane” located along the inner margin of the propodi of gnathopods 1, 2 ( Figs 71, 73 ) in both new species.

In S. anastasiae n. sp. a similar “squamiferous membrane” is located on inner face of both gnathopod propodi at the point of nail origin ( Fig. 72 ). Although this character is found in both sexes, males ( Fig. 74 ) and females ( Fig. 75 ) show some differences in the shape of scales, but which are probably related to age differences of individuals.

The term “squamiferous membrane” was used earlier by Henry & Magniez (1995) in a description of the morphology of the asellid isopod male pleopod 2. However, this morphological structure has apparently not been observed in crangonyctid amphipods until now. The “squamiferous membrane” may represent a complicated microtrich characterized by the fusion at the base of bunches of cuticular microtrichs of different lengths ( Mekhanikova & Takhteev 2008).

Figures

FIGURES 68 – 75. (68, 70, 71): Stygobromus mikhaili n. sp., male (2.6 mm): (68) tip of antenna 2; (70) propodus of gnathopod 2; (71) squamiferous membrane along inner margin, idem. (69, 72 – 75): Stygobromus anastasiae n. sp., female (3.0 mm), male (2.8 mm): (69) tip of antenna 2, female; (72) propodus of gnathopod 1, male; (73) squamiferous membrane along inner margin, idem; (74) squamiferous membrane in base of nail, idem; (75) squamiferous membrane in base of nail, female. SEM.