Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948

Marin, Ivan & Sokolova, Agniya, 2014, Redescription of the stygobitic shrimp Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948 (Decapoda: Caridea: Atyidae) from Agura River, Sochi, Russia, with remarks on other representatives of the genus from Caucasus, Zootaxa 3754 (3), pp. 277-298 : 278-291

Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948

( Figs. 1–10 )

Troglocaris schmidti jusbaschjani Birštein, 1948: 4 , figs. 1 [type locality: Agura river, Russian Caucassus, Russia].

Material examined. 30 non-ovigerous females, 5 males, Russian Federation, Krasnodarsky Kray, Sochi area, Mazesta region, Agura River, 39°48’40.54”E 43°32’57.26”N, about 1.4 km upstream from the sea, hydrogen sulfide bathes, coll. I. Marin & S. Anosov, 0 6 May 2012.

Description. Medium-sized shrimp with swollen, smooth, subcylindrical body ( Fig. 1 ). Males are similar in size and morphology to females ( Fig. 1 c). The main morphological differences from females lead in the structure of distal part of propodi and dactyli of pereiopods III and IV ( Figs. 5 , 8 ) and endopod of pleopods I and II ( Fig. 9 ). Carapace swollen, smooth, without dorsal or lateral carina, covered with small simple setae; rostrum ( Fig. 2 a–c) small, triangular, not reaching distal margin of basal antennular segment, sharply pointed and slightly curved upward distally, broad proximally, with feebly marked lateral lamina, dorsally and ventrally unarmed ( Fig. 2 a). Abdominal somites smooth, unarmed ( Fig. 1 ); tergites non-carinate, without dorsal lobes, not posteriorly produced; pleura of pleomeres I – IV posteroventrally and ventrally rounded; pleomere V small, with feebly developed pleura ( Fig. 1 ); distal and distoventral margins of pleomere VI sharply produced posterodorsally ( Fig. 2 f, d). Telson ( Fig. 2 f, d) stout, smooth, about 3 times as long as wide proximally, slightly tapering distally, with 2 pairs of small stout dorsal spines, each about 0.08 of telson length, inserted at about 0.5 and 0.7 telson length respectively; posterior margin slightly convex, with 4–5 pairs of distal spines, including a pair of short lateral spines, a pair of long intermediate spines and 2–3 pairs of slender medial spines about half of the length to intermediate spines.

Eyes ( Fig. 2 a–c) small, partly reduced, without pigment, swollen, subcylindrical; cornea rounded, partly reduced and feebly marked, without pigment; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula and antenna well developed. Antennula ( Fig. 2 a–c, h) with stout unarmed segments, basal peduncular segment robust, about 1.5 times longer than proximal width, without ventromedial tooth, distolateral angle with broadly produced blunt projection; stylocerite stout, bluntly rounded distally, overreaching the midlength of basal segment; second and third segments stout, unarmed, about as long as wide.

Antenna ( Fig. 2 a–c, i) stout; basicerite stout, about 1.5 times wider than long, with distolateral margin unarmed; carpocerite robust, about 1.5 times as long as wide, not reaching midlength of scaphocerite; scaphocerite well developed, broad, with small but well marked distolateral tooth, lamella bluntly rounded distally.

Mandible ( Fig. 3 a, b) well developed, without palp; molar process well-developed, relatively slender, with several small and large distodorsal teeth; incisor process slender, tapering distoventrally, with slender serrated sharp lamina distally. Maxillula ( Fig. 3 c) with well-developed simple palp armed with 2 setae distally, well developed, produced, blunt distally, dorsal lobe with completely fused lacinia, ventral lobe small, covered with curved setae distally. Maxilla ( Fig. 3 d) normal, with simple tapering small palp; endites stout, well-developed; basal endite basal endite feebly bilobed, furnished with elongated stiff setae; coxal endite obsolete; scaphognathite broad, furnished with short plumose setae. Maxilliped I ( Fig. 3 e) normal; epipod small, reduced; exopod small and slender, with expanded caridean lobe bearing plumose marginal setae; basal and coxal endites completely fused, excavate, furnished with long simple setae distally. Maxilliped II ( Fig. 3 f) with relatively robust segments; without epipod; exopod slender overreaching propodal segment, with long plumose setae distally; distolateral margin of propodus straight, dorsal margin convex, furnished with slender setae; dactylus about twice as long as broad, with straight distal margin, with numerous medium stout spines and numerous simple spines along distal margin. Maxilliped III ( Fig. 7 a) with slender segments; epipod stout, bluntly rounded; arthrobranch present; exopod slender, overreaching the distal margin of antepenultimate segment; antepenultimate segment slender, about 5 times as long as wide; penultimate segment about 5 times as long as wide, with straight lateral margins; ultimate (distal) segment slender ( Fig. 7 b), equal to penultimate segment, about 5 times as long as wide, tapering distally, with numerous tufts of short simple setae along ventral and lateral margins, with several long setae dorsally.

Pereiopods I equal in size and similar in shape, with relatively stouter segments in males ( Fig. 4 a), smaller females ( Fig. 6 e) and slender segments in large females ( Fig. 6 a) and, with smooth unarmed segments; coxa with well developed slender epipodite and tuft of setobranchs; basis about as long as wide, with well developed exopod overreaching carpo-meral articulation; ischium about twice longer than wide, with straight margins; merus slender, about twice as longer than wide, equal to ischium, with straight margins; carpus relatively stout in males ( Fig. 4 a), smaller females ( Fig. 6 e) and slender in large females ( Fig. 6 a), widening distally, slightly longer than merus, about as long as wide or twice longer than maximal width; palm relatively stout ( Figs. 4 a, 6 b, g), about as long as wide, subcylindrical in cross-section, smooth; fingers relatively stout, subcylindrical, smooth tapering distally, about 1.5 – 2 times as long as proximal width, with simple and straight cutting edges, with broad blunt distal margin, armed with a row of stout strong plumose setae.

Pereiopods II equal in size and similar in shape, similar to pereiopod I ( Fig. 4 b, 6 c, f), with relatively stouter segments in males ( Fig. 4 b), smaller females ( Fig. 6 f) and slender segments in large females ( Fig. 6 c), with smooth unarmed segments; coxa with well developed slender epipodite and tuft of setobranchs; basis about as long as wide, with well developed exopod overreaching carpo-meral articulation; ischium about as long as wide or twice longer than wide, with straight margins; merus slender, about as long as wide or twice longer than wide, usually equal to ischium or lightly longer, with straight margins; carpus relatively stout in males ( Fig. 4 b), smaller females ( Fig. 6 f) and slender in large females ( Fig. 6 c), widening distally, slightly longer than merus, about as long as wide up to 4 times longer than wide in large females; palm relatively stout ( Fig. 4 b, 6 c, f), similar to palm of pereiopod I, about as long as wide, subcylindrical in cross-section, smooth; fingers relatively stout, subcylindrical, smooth tapering distally, about 1.5 – 2 times as long as proximal width, with simple and straight cutting edges, with broad blunt distal margin, armed with a row of stout strong plumose setae.

Pereiopods III–V different in males and females. Pereiopod III in males ( Figs. 4 c) with relatively slender segments; coxa rectangular, about as long as wide, with tuft of setobranchs, with epipodite; basis about as long as wide, with well marked exopod almost reaching the midlenght of merus; ischium about twice as long as wide, with well marked distoventral spine; merus about 5 times as long as wide, with straight margins, with 3 – 4 well marked spines along ventral margin; carpus relatively slender, about 4 – 5 times as long as wide, slightly widening distally, about twice shorter than merus and slightly longer than half of the length of propodus, with bluntly projecting distodorsal margin overlapping carpo-propodal articulation; propodus about 7 – 8 times as long as wide, with straight margins, armed with 7 – 8 spines along proximal half of ventral margin and dense row of small simple setae in distal half of ventral margin ( Fig. 4 c, 5 a); dactylus ( Fig. 5 a) about twice longer than wide, biunguiculate, ventral margin armed with dense row of small simple setae in its proximal half and with several stout sharp triangular teeth in its distal half, main unguis ( Fig. 5 b) smooth, curved and sharp; accessory unguis triangular, sharp, slightly larger than ventral teeth, about twice shorter than main unguis, with well marked dorsal lacinia. Pereiopod IV in males ( Fig. 4 d) generally similar to pereiopod III; carpus unarmed. Pereiopod V in males ( Fig. 4 e) generally similar to pereiopods III and IV, but without armature on basal segments and exopod on basis; segments covered with simple setae dorsally and ventrally; propodus about 7 – 8 times as long as wide, with straight margins, armed with 8 – 10 spines along ventral margin and pair of more robust spines at distoventral angle; dactylus ( Fig. 5 d) with ventral margin armed with a dense “brush” consisting of small simple sharp setae; without accessory unguis, main unguis curved, triangular, sharp distally.

Pereiopod III in females ( Fig. 7 c, d) with relatively slender segments; coxa rectangular, about as long as wide, with tuft of setobranchs, with epipodite; basis about as long as wide, with well marked exopod almost reaching the midlength of merus; ischium about 1.5 times as long as wide, with well marked distoventral spine; merus about 4 times as long as wide, with straight margins, with 3 – 4 well marked spines along ventral margin; carpus relatively slender, about 3 times as long as wide, slightly widening distally, about twice shorter than merus and 1.5 times shorter than propodus, with bluntly projecting distodorsal margin slightly overlapping carpo-propodal articulation; propodus about 7 – 8 times as long as wide, with straight margins, armed with 8 – 10 spines along ventral margin and pair of more robust spines at distoventral angle ( Fig. 8 a); dactylus ( Fig. 8 a, b) about 1.5 – 2 times as long as wide, biunguiculate, ventral margin armed with stout sharp triangular teeth, main unguis smooth, curved and sharp; accessory unguis triangular, sharp, slightly larger than ventral teeth, about twice shorter than main unguis. Pereiopod IV ( Fig. 7 d) generally similar to pereiopod III; segments of pereiopod IV covered with simple setae dorsally and ventrally; merus armed with 3 – 4 ventral teeth; carpus armed with single distoventral tooth; propodus and dactylus similar to pereiopod III. Pereiopod V ( Fig. 7 f) generally similar to pereiopods III and IV, but without armature on basal segments and exopod on basis; propodus long and slender, about 8 times longer than wide, with 10 small teeth along ventral margin and a pair of distoventral teeth; dactylus ( Fig. 8 c) with ventral margin armed with a dense “brush” consisting of small simple sharp setae; without accessory unguis, main unguis curved, triangular, sharp distally.

Pleopods characteristic for the genus, without specific features. Pleopod I in males with endopod ( Fig. 9 d) bearing well marked appendix interna. Pleopod II in males ( Fig. 9 g) with well developed appendix interna and appendix masculine ( Fig. 9 h); appendix masculine covered with numerous small sharp stout simple spines. Pleopods I and II in females ( Fig. 9 a–c, e, f) normal, covered with small setae, characteristic for the genus without specific differentiating features.

Uropods ( Fig. 2 f) relatively stout, slightly exceeding telson; lateral margin of uropodal exopod ( Fig. 2 j) straight, with sharp triangular distolateral angle and large curved distolateral spine; dieresis simple.

Coloration. Body and appendages of shrimps are transparent whitish; cornea of eyes albescent; internal organs (gonads and hepatopancreas) are whitish or yellowish ( Fig. 10 ).

Ecology. Aggregations of shrimps were found in shallow hydrogen sulfide bathes of Agura River ( Fig. 10 ), a small river (about 10 kilometers length); hydrogen sulfide bathes are situated about 1.4 km far from the sea shore. Probably shrimps are washed out by groundwater through hydrogen sulfide springs and spend short time in these shallow bathes, which are located on a stretch for 400–600 meters from the springs. No shrimp specimens were found in the upper part of the river and in the remaining part of the river (about 2 km) before it falls into the Black Sea. The known area of the species distribution is about 2 square kilometers totally. Possibly, shrimps can feed on sulfide bacteria growing on their appendages (see Fig. 10 a, b, e) similar to alvinocaridid shrimps ( Decapoda : Caridea: Alvinocarididae ) inhabiting marine communities associated with deep water hydrothermal vents (“smokers”).

Measurements. The largest female has tbl.— 32 mm, pcl.— 16 mm; the largest male has tbl.— 25 mm, pcl.— 14 mm.

Distribution. The species is known exclusively from the type locality—hydrogen sulfide bathes on Agura River, Mazesta region, Sochi area, Russian Federation ( Fig. 11 , 16 ).

Figures

FIGURE 1. General view of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948: a — ovigerous female, pcl. 12 mm, b — non-ovigerous female, pcl. 6 mm, c — male, pcl. 12 mm.

FIGURE 2. Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, female, pcl. 12 mm (a, b, f – j), male, pcl 12 mm (c – e): a — front of carapace, dorsal view, b, c — front of carapace, lateral view, d, f — telson, e, g — distal margin of telson, h — antennula, i — antenna, j — distolateral margin of exopod of uropods.

FIGURE 3. Mouthpparts of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, female, pcl. 12 mm: a, b — mandible, c — maxillula, d — maxilla, e — maxilliped I, f — maxilliped II.

FIGURE 4. Pereiopods of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, male, pcl. 12 mm: a — pereiopod I, b — pereiopod II, c — pereiopod III, d — pereiopod IV, e — pereiopod V.

FIGURE 5. Dactyli of ambulatory pereiopods of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, male, pcl. 12 mm: a — distal part of propodus and dactylus of pereiopod III, b — distal part of dactylus of pereiopod III, c — distal part of propodus and dactylus of pereiopod IV, d — distal part of propodus and dactylus of pereiopod V.

FIGURE 6. Pereiopods I and II of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948: female, pcl. 12 mm (a – d), nonovigerous female, pcl. 7 mm (e – g): a, e — pereiopod I, b — chela of pereiopod I, c, f — pereiopod II, d, g — chela of pereiopod II.

FIGURE 7. Maxilliped III and ambulatory pereiopods of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, female, pcl. 12 mm (a – c, e, f), male, pcl. 12 mm (d): a — maxilliped III, b — same, distal segment, c, d — pereiopod III, e — pereiopod IV, f — pereiopod V.

FIGURE 8. Dactyli of ambulatory pereiopods of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, female, pcl. 12 mm: a, b — pereiopod III, c — pereiopod V.

FIGURE 9. Structure of pleopods I and II of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, female, pcl. 12 mm (a – c, e, f), male, pcl. 12 mm (d, g, h): a — pleopod I, b – d — endopod of pleopod I, e, g — pleopod II, f — endopod with appendix masculine, h — appendix masculine and appendix interna.

FIGURE 10. Alive coloration of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948, males, pcl. 10 and 11 mm, respectively (a, b), non-ovigerous females, pcl. 6 and 7 mm, respectively (c, d), ovigerous female, pcl. 11 mm (e – g): a – e — lateral view, f — dorsal view, g — carapace, dorsal view. Scale 2 mm.

FIGURE 11. The landscape of Agura river (a, b) and hydrogen sulfide bathes (c – g), where specimens of Troglocaris (Xiphocaridinella) jusbaschjani Birštein, 1948 were collected.

FIGURE 16. Schematic map of distribution of Caucasian stygobitic shrimp Troglocaris (Xiphocaridinella) species.