Zenkevitchia sandroruffoi, 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 : 12-20

Zenkevitchia sandroruffoi sp. nov.

urn:lsid:zoobank.org:act:707E6585-8A2E-47BA-802A-8349FAA1AAA2

Figs 2 , 4 F–H, 7–11

Diagnosis (both sexes)

Robust, middle-sized species of gammarid-like habitus (sexual dimorphism weakly pronounced, i.e., males usually larger than females, antenna 2 and both gnathopods sexually dimorphic). Antenna 1 short, reaching 40% length of body; antenna 2 short, reaching about 60% length of antenna 1, gland cone long, reaching half of peduncle of segment 4. Maxilla 1 inner plate triangular, with 16 plumose setae, outer plate of non-filtration type (?scraper type), with 22 multi-toothed, comb-like spines; palps symmetrical and reduced. Mandibular palp article 3 with 1 A group of 2 setae, 2 B setae, 13 D setae and 4 E setae. Gnathopods 1–2 small, with propodus not larger than corresponding coxa; palmar angles of both gnathopods defined, with a group of notched, strong corner spines; dactyli with 1 seta each along outer margin, nails long. Pereopods 5–7 bases with distinct postero-proximal lobes; inner margin of dactyli of pereopods 3–7 with 1 stiff, notched seta. Urosomites with dorsolateral groups of spines. Pleopods 1–3 with 2 coupling setae (retinacula), each accompanied with 1 seta (2+1). Uropod 1 rami sub-equal, outer ramus scarcely shorter than inner ramus. Uropod 3 short, 0.3× shorter than uropod 2, endopodite small, 0.6× shorter than exopodite. 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 6.0– 8.3 mm (♀), 8.0–12.5 (♂).

Etymology

This species is named in honor of Professor Sandro Ruffo (Museo Civico di Storia Naturale, Verona) for his outstanding contribution in the field of Amphipoda systematics.

Material examined

Holotype

GEORGIA: sequenced ♂, 8.0 mm, Sarma Cave (43°4158 N, 40°3633 E, approx.), 2346 m a.s.l., Muzykalnyj meander (sampling depth - 350 m), Arabika massif, Gagra District, Western Caucasus, 25 Aug. 2012, coll. E.E. Golubnichaya ( X44041 /Cr-1647-FEFU).

Paratypes

GEORGIA: ♂, 10.5 mm, ♀ (oostegites developed, weakly setose), 8.3 mm, Sarma Cave (sampling depth - 230 m), 28 Aug. 2012, coll. E.E. Golubnichaya ( X44042 /Cr- 1648-51 - FEFU); ♂, 12.5 mm, Trojka Cave (43°3933 N, 40°3625 E, approx.), 2333 m a.s.l., ~ 2-3 km SW of Sarma Cave (sampling depth - 30 m), 27 Aug. 2012, coll. E.E. Golubnichaya; ♀ (oostegites developed, weakly setose), 6.3 mm, Orlinoe Gnezdo Cave, (43°3855 N, 40°3637 E, approx.), 2126 m a.s.l., ~ 10 km SW of Sarma Cave (sampling depth - 75 m), 15 Sep. 2011, coll. L. T. Kharlamova.

Additional material

GEORGIA: specimens measured, partially dissected and stored in different vials (1-11/2sd-IBSS): 2 ♀♀ with developed oostegites, weakly setose, 7.0 mm, 8.0 mm, Sarma Cave, Muzykalnyj meander (sampling depth - 350 m), 25 Aug. 2012, coll. E.E. Golubnichaya; 2 ♀♀ with developed oostegites, weakly setose, 6.0 mm, 7.0 mm, Orlinoe Gnezdo Cave, (sampling depth - 75 m), 27 Aug. 2012, coll. E.E. Golubnichaya.

Differential diagnosis

Zenkevitchia sandroruffoi sp. nov. can easily be distinguished from the other cavernicolous typhlogammarids by the discriminative humps on its pleonal segments. See ‘Remarks’ section under sandroruffoi -group as well as the key below.

Description

Male (holotype)

BODY LENGTH. 8.0 mm.

GENERAL BODY MORPHOLOGY ( Fig. 9G, K ). Body smooth, with median and lateral, sparse, single setae, lacking dorsal cuticular elements but with distinct humps on pleonal segments. Head as long as first pereon segment; rostrum absent; inferior antennal sinus deep, rounded. Eyes absent. Urosomites 1–3 on dorsal surface with lateral spines and setae; armed with notched spines in the following manner: 1 (0-0), 2 (2-2), 3 (1-0-1). Epimeral plate 1: postero-ventral corner beveled; posterior and ventral margins convex; 2 stiff setae along ventral margin, 1 seta along posterior margin. Epimeral plate 2: posteroventral corner acuminate; posterior margin convex; ventral margin convex; 1 stiff seta along ventral margin, 2 setae along posterior margin. Epimeral plate 3: postero-ventral corner acuminate; posterior margin straight; ventral margin straight; 1 stiff seta along ventral margin, 1 seta along posterior margin. Telson: width:length ratio is 1:0.6; cleft entirely; 2 apical spines per lobe present, 0.3–0.4× telson length, each accompanied by 1 or 2 plumose setae.

ANTENNAE ( Figs 2 , 7 A–B). Antenna 1 0.38× of body length; main flagellum with up to 23 articles; each article with 5–9 short setae; peduncular articles in ratio 1:0.7:0.4; proximal article of peduncle distally with 1 medial set of long setae; accessory flagellum 3-articulated. Length ratio of antenna 1 to antenna 2 is 1:0.6; flagellum of antenna 2 with 10 articles, each article densely setose; length ratio of peduncle articles 4 and 5 is 1:0.8; flagellum 0.4× longer than peduncle (articles 4+5); peduncular articles 4 and 5 with sets of long, stiff setae on lateral and medial faces; gland cone long, reaching half of peduncle of segment 4.

MOUTH PARTS. Typical gammarid, except for unusual maxilla 1 ( Figs 4H , 8 A–E, G–L). Labrum rounded, clypeus unfused, longer than broad. Inner lobes of labium absent, outer lobes broad with stiff curved setae marginally, mandibular process distinct (narrow). Left mandible: incisor with 5 teeth, lacinia mobilis with 4 teeth; between lacinia and molar a row of 14 serrate spines. Right mandible: incisor process with 4 teeth, lacinia mobilis bifurcate, with several small denticles, between lacinia and molar a row of 12 serrate spines; triturative molar process with long lanose seta. Mandibular palp article 2 slightly longer than article 3 (distal); proximal palp article without setae; second article with 12 setae; distal article narrowed, with 1 A group of 2 setae, 2 B setae, 13 D setae and 4 E setae. Maxilla 1 palp reduced, distal article with 4 or 5 apical setae (both palps sub-symmetrical); outer plate with 22 multi-toothed spines; inner plate triangular, with 16 plumose setae. Maxilla 2 inner plate smaller than outer one with, oblique row of 11 plumose setae; both of them apically with numerous setae in two rows. Maxilliped palp article 2 narrow, with about 55 setae along inner margin; article 3 narrow, with 2 dense sets of setae on inner face; article 4 (distal) with dorsal seta, bearing 5 setae at the nail base, nail shorter than pedestal; outer plate with 15 flattened naked spines and 7 long plumose setae on apex (3 of them flattened); inner plate with 3 strong spines (1 supplemental spine on medial face) and 8 stiff, naked setae on apex, 27 plumose setae on ventral face, 10 stiff denticulate setae in 2 rows on dorsal face. Foregut lateralia with 15 strong pectinate spines, with densely setose row of stiff setae.

COXAL PLATES, GILLS ( Figs 7 D–E, 9A–B, 10A–C). Coxal plate 1 of rectangular shape, antero-ventral margin extended, with 3 setae. Coxal plate 2 of rectangular shape, antero-ventral margin narrowed, with 3 setae. Coxal plate 3 width:depth is 0.5:1, along antero-ventral margin with 2 setae. Coxal plate 4 of sub-quadrate shape, width:depth is 0.9:1; posteriorly with prominent excavation, along ventral margin 6 setae. Coxal plates 5–7 progressively smaller towards the posterior. Coxal plates 5–6: only anterior lobe well-developed; posterior margin pointed with 2 setae. Coxal plate 7 sub-triangular, anterior part beveled, along posterior margin with 3 setae in shallow serration. Coxal gills 2–7 stalked, large but progressively smaller towards the posterior; gills 2–4 triangular, gills 5–7 saccular or irregularly ovoid. GNATHOPODS 1–2 ( Figs 7 D–G). Gnathopod 1: ischium with postero-distal set of 6 short setae. Carpus 0.4× length of basis and 0.56× length of propodus; anterior margin of carpus with 1 group of setae; carpus posteriorly with 2 sets of lateral setae. Propodus sub-rectangular, palm straight, with cutting margin smooth and shorter than posterior margin; along posterior margin 5 simple setae with 1 pair of notched spines; anterior margin with 2 sets of setae, antero-distal group with 4 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle with a group of 4 distally-notched, strong corner spines on both faces; nail long, 0.4× total length of dactylus, 1 seta along anterior margin and 3 setules at hinge. Gnathopod 2: basis width:length is 0.34: 1. Ischium with 2 sets of postero-distal setae. Carpus 0.3× length of basis and 0.56× length of propodus; anterior margin of carpus with 1 distal set of setae; carpus posteriorly with 3 lateral sets of setae. Propodus small (compared to the body) and same length as propodus of gnathopod 1; propodus sub-rectangular, palm straight, with cutting margin smooth and shorter than posterior margin; posterior margin with 4 sets of stiff setae; anterior margin with 2 sets of setae; antero-distal group with 5 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle with a group of 5 distally-notched, strong corner spines on both faces; dactylus similar to that of gnathopod 1.

PEREOPODS 3–7 ( Figs 9 A–B, 10 A–C). Lengths of pereopods 3–4 equal. Dactylus 4 0.5× propodus 4; nail length 0.5× total dactylus length. Dactyli 3–4 with dorsal plumose seta; inner margin with 1 stiff seta and 1 thin seta at hinge. Lengths of pereopods 5:6:7 is 0.9:1:0.9. Pereopod 7 length 0.47× body length. Bases 5–7 narrowed distally; posterior margin with postero-proximal lobes; posteriorly marginal serrations with stiff setae (with thin setae in basis 5); anteriorly 3 notched spines. Dactylus 7 length 0.37× propodus 7 length. Dactyli 5–7 with dorsal plumose seta; inner margin with 1 stiff, notched seta and 1 thin seta at hinge.

PLEOPODS ( Fig. 9 C–F). Pleopods 1–3 sub-equal, each with 2 coupling setae accompanied by 1 stiff seta; peduncular articles fringed with long, thin setae; proximal article of inner rami fringed with 3 bifurcate setae. Pleopods 1–3 rami with 10–15 articles each.

UROPODS ( Figs 2 , 9 H–J). Uropod 1 protopodite without basofacial spine, with 3 dorso-lateral spines and 1 dorso-medial spine; exopodite:endopodite length is 0.95:1; rami straight and unarmed along outer margins; both with 5 strong, notched spines apically and sub-apically. Uropod 2 exopodite slightly curved and 0.2× shorter than endopodite. Uropod 3 protopodite with 2 groups of strong notched spines on apex; endopodite 0.4× of protopodite length, with 3 long setae apically; exopodite 1.16× longer than protopodite, with 2 groups of lateral spines, long simple setae along inner margin, 3 spines and 4 setae apically.

Female (paratype X44043 /Cr-1649-FEFU)

Body length 8.3 mm, with sexually dimorphic characters ( Fig. 11 ). Smaller than male, with more slender body. Antenna 2 slender, peduncular article 4 with bundle of long setae on distal margin. Gnathopods 1 and 2: bases slender, with densely setose posterior margin; propodi sub-similar, sub-rectangular, but propodus of gnathopod 2 larger than on gnathopod 1; palmar margins sub-transverse, palm straight, with cutting margin acanthaceous; nail very long, 0.5× total length of dactylus. Uropod 3 weakly armed; endopodite with 2 long setae apically. Telson with 1 spines per lobe. Oostegites 2–5 on gnathopod 2 and pereopods 3–5, very broad, with marginal setae.

Variability

Flagellum of antenna 1 with 21–23 articles. Uropod 3 endopodite with 2–3 setae apically. One individual had an abnormal 2-articulated accessory flagellum. The population of Z. sandroruffoi sp. nov. inhabiting streams in the Orlinoe Gnezdo cave differs slightly by having a smaller body size and further shortened antenna 1, but are otherwise indistinguishable.

Ontogenetic variation

Almost all adults presented with significantly threadbare ( Fig. 8F ) or broken spines on the outer plate of maxilla 1. Thus, the first three of the most powerful spines turned out to be broken off in almost of all of the specimens.

Distribution and ecology

Zenkevitchia sandroruffoi sp. nov. inhabits aquatic biotopes in several caves ( Fig. 1 ) in the Eastern Arabika massif and it apparently avoids deep cave habitats. This species was observed in the Sarma Cave not deeper than - 350 m ( Fig. 2 ), in the nearby Trojka cave at a depth of - 30 m and in the notfar distant Orlinoe Gnezdo cave at - 75 m. The setae on the antennal appendages of all specimens were densely covered ( Fig. 7C ) with attached filamentous algae (cyanobacteria?). The nature of the morphological variability and divergence of COI gene sequences (pairwise distances <2.2%) suggests that, in the Orlinoe Gnezdo cave, the other population of the same species is present.

Figures

Fig. 2. Vertical distribution of amphipod species in the Sarma Cave. Map adapted from Sidorov et al. (2014), compiled by V.V. Sukhachev.

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. 9. Zenkevitchia sandroruffoi sp. nov. Holotype, ♂, 8.0 mm, X44041/Cr-1647-FEFU. A. Pereopod 3. B. Pereopod 4. C. Pleopod 1. D–F. Coupling setae of pleopods 1–3. G. Epimeral plates 1–3. H. Uropod 1. I. Uropod 2. J. Uropod 3. K. Telson.

Fig. 7. Zenkevitchia sandroruffoi sp. nov. Holotype, ♂, 8.0 mm, X44041/Cr-1647-FEFU. A. Antenna 1. B. Antenna 2. C. Barbate seta with attached filamentous algae. D. Gnathopod 1. E. Gnathopod 2. F–G. Palmar margins of gnathopods 1 and 2 propodi.

Fig. 8. Zenkevitchia sandroruffoi sp. nov. — A–E, G–K. Holotype, ♂, 8.0 mm, X44041/Cr-1647-FEFU. A. Left mandible. B. Right mandible. C. Lower lip. D. Upper lip. E. Maxilla 1. G. Palp of right maxilla 1. H. Maxilla 2. I. Maxilliped. J. Inner plate of maxilliped, inner face. K. Inner plate of maxilliped, outer face. — F, L. Paratype, ♀, 8.3 mm, X44043/Cr-1649-FEFU. F. Outer plate of maxilla 1. L. Outer plate of maxilliped.

Fig. 10. Zenkevitchia sandroruffoi sp. nov. Holotype, ♂, 8.0 mm, X44041/Cr-1647-FEFU. A. Pereopod 5. B. Pereopod 6. C. Pereopod 7.

Fig. 11. Zenkevitchia sandroruffoi sp. nov. Paratype, ♀, 8.3 mm, X44043/Cr-1649-FEFU. A. Antenna 1. B. Antenna 2. C. Gnathopod 1. D. Gnathopod 2. E–F. Palmar margins of gnathopods 1 and 2 propodi. G. Uropod 1. H. Uropod 2. I. Uropod 3. J. Telson.

Fig. 1. Distribution map of Typhlogammaridae species and Anopogammarus in the Transcaucasia. 1. Zenkevitchia sandroruffoi sp. nov. 2. Adaugammarus pilosus gen. et sp. nov. 3. Zenkevitchia sp. sensu Jaume in Sendra & Reboleira (2012). 4. Zenkevitchia admirabilis (complex of species). 5. Zenkevitchia yakovi Sidorov, 2015. 6. Zenkevitchia revazi Birstein & Ljovuschkin, 1970, comb. resurr. 7. Anopogammarus birsteini Derzhavin, 1945.