Kruberia relicta Sidorov, 2018

Sidorov, Dmitry, Taylor, Steven J., Sharina, Svetlana & Gontcharov, Andrey, 2018, Zenkevitchiidae fam. nov. (Crustacea: Gammaroidea), with description of new subterranean amphipods from extremely deep cave habitats, Journal of Natural History (J. Nat. Hist.) 52 (23 - 24), pp. 1509-1535 : 1525

Kruberia relicta Sidorov sp. nov.

( Figures 2c , 4b , 9–13 )

Zenkevitchia sp. sensu Jaume in Sendra and Reboleira, 2012: 224, fig. 6B.

non Kruberia abchasica Sidorov and Samokhin, 2016: 375 , figs 1–3.

Material examined

Holotype specimen ( X45485 /Cr-1829- FEFU), adult female (oostegites developed, setose), ~28.0 mm, Krubera Cave , (sampling depth – 2175 m, siphon ‘Dva Kapitana’), Arabika massif, Orto-Balagan valley , Gagra District , Western Caucasus, Abkhazia, 10 August 2013, coll. G. Samokhin.

Etymology

Species epithet ( relicta, Latin ) is an adjective meaning ‘relict’.

Diagnosis (female)

Subterranean (stygobiont) eyeless species of Kruberia with modified mouthparts and elongated limbs adapted to living in a cave lake (lake ecomorph). Body length: 28.0 mm. See section ‘Taxonomic comments’ and identification key below.

Description

Holotype ( X45485 /Cr-1829- FEFU). General body morphology ( Figures 4b , 10 , 11 , 12 , 13a, f, g ). Body stout, smooth, lacking dorsal cuticular elements. Head as long as pereonite I; rostrum indistinct; inferior antennal sinus shallow. Eyes absent. Coxal plates I– IV deeper than broad. Coxal gills II–VII stalked, saccular, large. Oostegites II – V broad, with long marginal setae, oostegite V smallest. Epimeral plates I– III with medial and lateral groups of setae; ventral margins bearing 1 or 3 notched spines. Urosomites I – III on dorsal surface without cuticular tubercles, armed with notched spines in the following manner: I (1–1), II (4–1–1–2), III (1-1); urosomite III elongated, nearly twice as long as adjacent urosomite II. Telson entirely cleft, 2 apical spines per lobe, each accompanied by 6–8 setae. Antennae ( Figure 9a, b ). Antenna I as long as body, about 2.0× longer than antenna II; peduncular articles I– III in ratio 1:1:0.7; primary flagellum with 62 articles; accessory flagellum 6-articulate. Antenna II: gland cone short; peduncular articles IV and V densely setose with tight bundles of stiff setae on lateral and medial faces; peduncle (articles 4 + 5) 1.1 times longer than flagellum, which consist of 16 articles; calceoli absent. Mouth parts ( Figure 9c–j ). Mandibles subequal: right mandible incisor process with 4 teeth, lacinia mobilis bifurcate, with several denticles, between lacinia and molar a row of 6 serrate spines; triturative molar process with seta; mandibular palp article 2 longer than article 3 (distal); proximal palp article without setae; second article with 42 setae on medial and 6 setae on lateral margins; distal article with 5 A-groups of 4, 7, 8, 8 and 5 setae, respectively, 4 B-groups of 3, 5, 5 and 6 setae, respectively, 45 D-setae and 6 E-setae. Maxilla I inner plate with 24 plumose setae, outer plate with 16 comb-like, multi-toothed spines; palp relatively long, both asymmetric; distal palp article with 6 spines and 2 simple setae on apical and sub-apical margin, 2 setae on lateral margin. Lower lip: outer lobes broad, rounded, mandibular process narrow, inner lobes absent. Maxilla II and maxilliped without peculiarities. Gnathopods ( Figure 10 ). Gnathopod I: carpus (article 5) stout, with group of stiff, serrate setae on inner face; propodus (article 6) oblong, coniform, palm convex, palmar margin with short, notched (bifid) setae along outer and inner faces, palmar angle undefined, a group of 12 distally notched, strong spines on both faces; dactylus very long, 1 seta along anterior margin, with 2 minute setules at hinge. Gnathopod II similar to gnathopod I, but a little larger; propodus armed with a group of 7 distally notched, strong spines on both faces; dactylus similar to that of gnathopod I. Pereopods ( Figures 11 , 12 ). Pereopods III and IV sub-similar; bases narrow, with sets of short setae on anterior and long setae on posterior margins. Lengths of pereopods V: VI: VII is 0.85:1: 0.9. Pereopod VI length 0.8× body length. Bases V –VII narrow, posterior margin without postero-distal lobes; marginal serrations with short setae posteriorly and with 2–6 groups of notched spines accompanied with setae anteriorly; dactylus length about 0.1× of propodus length, inner margin with 1 stiff seta and 1 thin seta at hinge. Pleopods and uropods ( Figure 13b–e ). Pleopods I – III sub-equal, each with 2 coupling setae accompanied by 4 stiff setae; peduncular articles fringed with long, thin setae; proximal article of inner rami fringed with 10 bifurcate setae; rami with 30–39 articles each. Uropod I protopodite with basofacial spine, with 4 dorso-lateral spines and 3 dorso-medial spines; endopodite almost twice shorter then protopodite, with 2 spines on outer margin; exopodite slightly longer than endopodite, bearing 1 spine 3 sets of setae on lateral margins; rami with 5 spines apically and sub-apically. Uropod II exopodite 0.6 shorter than protopodite and as long as endopodite; in distal part rami armed similar to that of uropod I. Uropod III magniramus, rami lanceolate; endopodite slender, narrowed distally, 1.78 of protopodite length, densely fringed with setae; exopodite 0.6 longer than endopodite, with 4 spines and about 26 sets of setae on outer margin, with sets of setae along inner margin, 4 spines and about 25 setae in terminal part.

Figures

Figure 2. Outline map of the Krubera Cave profile, showing position of the sampling sites and relative sizes of amphipods. Altered and adapted from Klimchouk (2012). (a) Adaugammarus kasiani sp. nov.; (b) Kruberia abchasica; (c) Kruberia relicta sp. nov.; (d) to provide a sense of scale, a silhouette of the world’s tallest building at 828 m (Burj Khalifa, Dubai, United Arab Emirates).

Figure 4. Habitus of examined specimens: (a) Adaugammarus kasiani sp. nov., holotype X47640/Cr-2236- FEFU, male, 17.0 mm; (b) Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm.

Figure 9. Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm: (a) antenna I; (b) antenna II; (c) right mandible; (d) third segment of palp, ventral view; (e) maxilla II; (f) maxilla I; (g) palp of left maxilla I; (h) upper lip; (i) lower lip; (j) maxilliped. Scale bars = 0.2 mm.

Figure 10. Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm: (a) gnathopod I; (b) gnathopod II. Scale bar = 0.4 mm.

Figure 11. Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm: (a) pereopod III; (b) pereopod IV. Scale bar = 0.4 mm.

Figure 12. Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm: (a) pereopod V; (b) pereopod VI; (c) pereopod VII. Scale bar = 0.4 mm.

Figure 13. Kruberia relicta sp. nov., holotype X45485/Cr-1829-FEFU, female, 28.0 mm: (a) epimeral plates I–III; (b) pleopod I; (c) uropod I; (d) uropod II; (e) uropod III; (f) telson; (g) first and second segment of urosome, dorsal view. Scale bar = 0.4 mm.