Adaugammarus, Sidorov & Gontcharov & Sharina, 2015

Sidorov, Dmitry A., Gontcharov, Andrey A. & Sharina, Svetlana N., 2015, A new genus and two new species of cavernicolous amphipods (Crustacea: Typhlogammaridae) from the Western Caucasus, European Journal of Taxonomy 168, pp. 1-32 : 20

Genus Adaugammarus gen. nov.

urn:lsid:zoobank.org:act:C38A81BD-4918-46B0-BD37-4BF7A6669E8F

Type species

Adaugammarus pilosus sp. nov., by monotypy.

Generic diagnosis

Stout and gentle, large-sized species of gammarid-like habitus (sexual dimorphism marked, i.e., some males larger than females, antenna 2, both gnathopods and uropods 1–3 sexually dimorphic). Antenna 1 short, reaching 50% length of body; antenna 2 short, reaching about 50% length of antenna 1, gland cone short. Maxilla 1 inner plate trapezoidal, with 10 plumose setae, outer plate of non-filtration type (?scraper type), with 14 multi-toothed, comb-like spines; palps asymmetric and long. Mandibular palp article 3 with 2 A groups, 2 B groups, 13 D setae and 4 E setae. Gnathopods 1–2 relatively small, with propodus not larger than corresponding coxa; palmar angles of both gnathopods undefined, each bearing a group of notched, strong palmar spines; dactyli with 1 seta along outer margin, nails rather long. Pereopods 5–7 bases distinctly broader in proximal part; inner margin of dactyli of pereopods 3–7 with 1 stiff seta. Urosomites with dorsolateral groups of spines. Pleopods 1–3 with 2 coupling setae (retinacula), each accompanied by 1 seta (2+1). Uropods 1–3 extremely setose, with dense bundles of long swirling setae; uropod 1 exopodite broad and curved; uropod 3 exopodite broad, 1.6× longer than protopodite (in males). Telson with 1 or 2 distal spines per lobe. Coxal gills 2–7 stalked, triangular or sacciforme, largest on gnathopod 2, successively smaller on pereopods 3 to 7, gill 7 the smallest. Body length 12.5–16.5 mm (♀♀), 11.5–17.5 (♂♂).

Etymology

The generic epithet ( Adaugammarus ) is derived by the combination of Adau, the name of fearsome malicious giants in Abkhazian mythology, with Gammarus , a closely related genus. Gender masculine.

Discussion of affinities

Adaugammarus gen. nov. is an interesting taxon possessing features typical for a number of groups, but tending more towards Typhlogammarus because of the following characters: lateral cephalic lobe with recess, propodi of both gnathopods with palmar angles undefined, uropod 3 exopodite distinctly broad in males. Adaugammarus gen. nov. is related to the sandroruffoi -group of Zenkevitchia and Typhlogammarus in the similar structure of the outer plate, which has 14 multi-toothed spines. The urosomal segments are armed in a similar manner to those of Zenkevitchia . Adaugammarus gen. nov. differs from Metohia in the absence of dorsal cuticular elements and from Accubogammarus in having a short antennal gland cone, in variramus uropod 3, and differs in having 14 multi-toothed spines on the outer plate of maxilla 1, in contrast to the 38 very densely toothed spines present in Accubogammarus . Superficial comparison with the other “deep dweller”, cf. Zenkevitchia sp. sensu Jaume in Sendra & Reboleira (2012) from the Krubera-Voronja cave, revealed that the two taxa differ significantly from each other by the body shape and by the extremely large body size (~19.0–28.0 mm in females from Krubera) (pers. obs.).