Anopogammarus birsteini Derzhavin, 1945

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 : 6-11

Anopogammarus birsteini Derzhavin, 1945

Figs 4 A–E, 5–6

Anopogammarus birsteini Derzhavin, 1945: 34 , pl. 2.

Anopogammarus birsteini – Birstein & Ljovuschkin 1967: 1512; 1970: 1478, figs 4–6. — Stock 1973: 339. — Bousfield 1977: 291. — Karaman & Barnard 1979: 142. — Barnard & Karaman 1980: 8. — Barnard & Barnard 1983: 502. — Ruffo 1995: 450. — Karaman & Ruffo 1995: 159, 160.

Material examined

GEORGIA: 1 ♀, 1 ♂, Western Caucasus, Gagra District, near Goluboe Lake (43°3508 N, 40°4119 E). Specimens, completely dissected and mounted on a single slide per number: ♀ (oostegites initial, nonsetose) 9.0 mm, ♂ 8.5 mm, 15 Jun. 2015, 133 m a.s.l., springs, coll. D.M. Palatov ( X44039 /Cr- 1645- 46 - FEFU).

Additional material examined

GEORGIA: 5 ♀♀ (6.0 mm, 3x 7.0 mm, 7.5 mm; oostegites initial, non-setose), 5 ♂♂ (3x 6.0 mm, 7.5 mm, 9.0 mm), 3 juv., specimens measured, partially dissected and stored in different vials (1-12/1sd-IBSS), same data as above.

Remark

Although A. birsteini was described by Derzhavin (1945) based on an 8.0 mm female and was subsequently redescribed in detail ( Birstein & Ljovuschkin 1970) based on both sexes, we further introduce an amended diagnostic description to emphasize some important characters.

Diagnostic description

SIZE. Female body length 9.0 mm and male, body length 8.5 mm ( X44039 /Cr- 1645-46 -FEFU). Robust, large-sized species of gammarid-like habitus (sexual dimorphism weakly pronounced, i.e., females larger than males). 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 6.0–17.0 mm (♀), 6.0–14.0 mm (♂).

GENERAL BODY MORPHOLOGY ( Figs 4 A–D, 6G). Body smooth, lacking dorsal cuticular elements. Head as long as first pereon segment; rostrum absent; inferior antennal sinus shallow, sub-rounded. Eyes absent. Pleosomites and urosomites on dorsal surface with lateral groups of spines and setae; medial elements absent. Dorsal surface of urosomites 1–3 armed with robust spines in the following manner: 1 (3-0-0-3), 2 (2-0-0-2), 3 (1-0-1). Epimeral plate 1: postero-ventral corner prominent; posterior and ventral margins convex; 2 stiff setae along ventral margin, 2 setae along posterior margin. Epimeral plate 2: postero-ventral corner acuminate; posterior and ventral margins convex; 5 stiff setae in two rows along ventral margin, 1 seta along posterior margin at corner. Epimeral plate 3: postero-ventral corner acuminate; posterior margin concave; ventral margin convex; 4 stiff seta along ventral margin, 2 setae along posterior margin. Telson as long as broad; cleft entirely; 2 or 3 apical spines per lobe present, these are 0.2× telson length, each accompanied by setae. Antennae ( Figs 4A , 5 A–B). Antenna 1 0.65× of body length; main flagellum with up to 30–32 articles; almost all flagellar articles bearing small aesthetascs accompanied by 2–8 short setae; peduncular articles in ratio 1:0.7:0.4; proximal article of peduncle with 3 sets of short setae along ventral margin; accessory flagellum 3- or 4-articulated. Length ratio of antenna 1 to antenna 2 is 1:0.5; flagellum of antenna 2 with 11–15 articles, each article densely setose; length ratio of peduncle articles 4 and 5 is 1:0.9; flagellum as long as peduncle (articles 4+5); peduncular articles 4 and 5 with sets of long stiff setae along ventral margin; gland cone short.

MOUTH PARTS (typical gammarid, Figs 5 E–G). Maxilla 1 palp longer than outer plate, distal article with 5 apical and 2 sub-apical setae (both palps asymmetric, right palp broader, with 4–5 strong spines and 2 plumose setae on apex and 1–2 setae on outer margin); outer plate with 12–14 spines (5 poorly toothed and 9 multi-toothed); inner plate trapezoidal, with 12 plumose setae. Foregut lateralia with 13 strong pectinate spines and densely setose row of stiff setae.

GNATHOPODS 1–2 ( Fig. 5 C–D). Gnathopod 1: propodus almond-shaped, palm convex, with cutting margin acanthaceous and 2× longer than posterior margin; along posterior margin two sets of simple setae; antero-distal group of anterior margin with 10 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle undefined, a group of 10 distally-notched strong spines on both faces (with 2 strong mid-palmar spines in the place where tip of nail close); nail long, 0.25× total length of dactylus, 1 seta along anterior margin, with 4 setules at hinge. Gnathopod 2: propodus small (compared to the body) and slightly larger than propodus of gnathopod 1; propodus almond-shaped, palm convex, with cutting margin acanthaceous and as long as posterior margin; posterior margin with 6 sets of stiff setae; antero-distal group of anterior margin with 10 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle undefined, a group of 8 distally-notched strong spines on both faces (with 2 strong mid-palmar spines in the place where tip of nail close); dactylus similar to that of gnathopod 1.

PLEOPODS ( Fig. 6 A–B). Pleopods 1–3 sub-equal, each with 2 coupling setae (retinacula) accompanied by 1–3 stiff setae; peduncular articles fringed with long, thin setae; proximal article of inner rami fringed with 4 setae. Pleopods 1–3 rami with 15–19 articles each.

UROPODS ( Figs 4A , 6 C–F). Uropod 1 protopodite with 1 basofacial spine, 3 dorso-lateral spines and 2 dorso-medial spines; exopodite as long as endopodite; rami straight, with single spines along outer margins; both with 5 spines apically and sub-apically (two of them strong). Uropod 2 endopodite slightly shorter than exopodite. Uropod 3 protopodite with 3 groups of spines on apex; endopodite as long as protopodite, with 1 spine and 7 long setae apically; exopodite 2-articulated, about 2.2× longer than protopodite, with 3 groups of lateral spines, 6 groups of long simple setae along inner margin; proximal article with 4 spines and about 10 long setae on apex, terminal article short, 0.09× as long as proximal article, with 6 long simple setae sub-apically.

Discussion of affinities

Describing the monotypic genus Anopogammarus Derzhavin (1945) noted a lack of eyes in A. birsteini as the only difference from the genus Gammarus and considered this feature characteristic. Later, Birstein & Ljovuschkin (1970) re-described Anopogammarus birsteini in detail and considered this species, along with Metohia carinata Absolon, 1927 , as derived from Gammarus , implying a subgeneric status for the genera Anopogammarus and Metohia . However, according to their view, Zenkevitchia revazi occupies an intermediate position between the specialized Zenkevitchia admirabilis and Gammarus ( Stock 1973) . Subsequently, Karaman & Barnard (1979) transferred Z. revazi to Anopogammarus , based on the non-moplike structure of maxilla 1 and reduced palps in the former species. Later, the same authors ( Barnard & Karaman 1980) again confirmed that Anopogammarus , along with the rest of the taxa placed in the Family group 2 ( Typhlogammarus group, hypogean large gammarids) sensu Bousfield (1977), has no strong distinction from the Gammarus-Echinogammarus group (see Barnard & Karaman 1980: 7–9). Ruffo (1995) and Karaman & Ruffo (1995), describing two genera of cavernicolous amphipods ( Albanogammarus and Sinogammarus from Albania and Southwest China, respectively), discussed the position of the new taxa in depth and hypothesized an obvious affinity with Anopogammarus .

The revision of the group cannot be considered as completed, because the genus Anopogammarus is heterogeneous and needs to be split. We propose transferring Anopogammarus revazi to the genus Zenkevitchia ( Zenkevitchia revazi Birstein & Ljovuschkin, 1970 , comb. resurr.) and to the newly proposed group ( sandroruffoi -group). The monotypic genus Anopogammarus based on Anopogammarus birsteini Derzhavin, 1945 , however, should be considered a component of the family Gammaridae . As the above-mentioned authors, we believe that the monotypic genus Anopogammarus has an affinity to Albanogammarus and Sinogammarus . This assumption is based on the following shared features: the structure of the anterior margin of the cephalon (lateral interantennal lobes slightly subquadrate); powerful dorsal armament of urosomal segments; antenna 1 with small aesthetascs in males (? lacking in Albanogammarus ); calceoli on antenna 2 absent; article 1 of antenna 2 being rather large, bearing short setae, and antennal gland cone short; structure of maxilla 1 (outer plate with multi-toothed non-falcate spines and palps clearly asymmetric); uropod 3 long and with 2-articulated outer ramus.

Figures

Fig. 4. — A–D. Anopogammarus birsteini Derzhavin, 1945. ♀, 9.0 mm, X44039/Cr-1645-FEFU: A. Habitus from left side. B. Urosome. C. Head. D. Metasomal and urosomal segments with telson. — E–G. Zenkevitchia sandroruffoi sp. nov. Paratype, ♀, 6.3 mm, X44045/Cr-1651-FEFU. E. Lateralia. F. Head. G. Urosome. — H–K. Adaugammarus pilosus sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr- 1652-FEFU. H. Lateralia. I. Head. J. Urosome. K. Lateralia.

Fig. 5. Anopogammarus birsteini Derzhavin, 1945. ♀, 9.0 mm, X44039/Cr-1645-FEFU. A. Antenna 1. B. Antenna 2. C–D. Palmar margins of gnathopods 1 and 2 propodi. E. Maxilla 1. F. Outer plate of maxilla 1. G. Palp of right maxilla 1.

Fig. 6. Anopogammarus birsteini Derzhavin, 1945. ♀, 9.0 mm, X44039/Cr-1645-FEFU. A. Pleopod 2. B. Coupling setae of pleopod 2. C. Uropod 1. D. Uropod 2. E–F. Uropod 3. G. Telson.