Xiphocaridinella ablaskiri ( Birštein, 1939 )

Marin, Ivan, 2018, Cryptic diversity of stygobiotic shrimp genus Xiphocaridinella Sadowsky, 1930 (Crustacea: Decapoda: Atyidae): the first case of species co-occurrence in the same cave system in the Western Caucasus, Zootaxa 4441 (2), pp. 201-224 : 204-213

Xiphocaridinella ablaskiri ( Birštein, 1939)

( Figs. 4–8 )

Troglocaris schmidti ablaskiri Birštein, 1939: 961 , figs. 1, 2 [type locality: Otap Cave, AbkhaZia].

Material examined. Neotype, male, ZMMU Ma 3572, Western Caucasus, Abkhazia, Ochamchira District, Otap village, Otap Cave (= Golova Otapa), 42°55'19.3"N 41°32'19.6"E, 240–253 meters above the sea level, in underground cave stream, hand net sampling, coll. I. Marin & I. Turbanov, 25 August 2015 ; 5 non-ovigerous females, 3 males ( LEMMI)—same locality and date as holotype ; 10 non-ovigerous females, 7 males ( LEMMI)— Abrskil Cave (= Otapskaya, Achkshe-Tyz-Gua), 42°55'14.0"N 41°33'17.0"E, 222–230 meters above the sea level, in underground cave stream, hand net sampling, coll. I. Marin & I. Turbanov, 25–26 August 2015 ; 1 ovigerous female, 1 non-ovigerous female and 1 male ( LEMMI)— Samshitovaya Cave , 42°55'32.8"N 41°32'26.0"E, about 354 meters above the sea level, in small subterranean puddle, hand net sampling, coll. I. Turbanov, 21August 2015 ; 1 non-ovigerous female, 2 juveniles ( LEMMI)— Uatapakhy Cave (=Kolodez, Kolodez 75 meters, Kolodez above Otap Cave), 42°55'24.9"N 41°32'21.7"E, about 297 meters above the sea level, in small subterranean puddle, hand net sampling, coll. I. Turbanov, unknown date.

Description. Small-sized shrimp with swollen, smooth, subcylindrical body, males slightly smaller than females ( Fig. 8 ). Carapace ( Fig. 4 ) swollen, smooth, without dorsal or lateral carina, covered with small simple setae, sometimes small supraocular teeth present (see Fig. 4 b, d ); rostrum ( Fig. 4 ) small, triangular, not reaching distal margin of basal antennular segment, bluntly pointed and slightly curved upward distally, broad proximally, with relatively marked lateral lamina, dorsally and ventrally unarmed ( Fig. 4 a–e ), sometimes tiny distodorsal rostral spine present ( Fig. 4 f ).

Abdominal somites smooth, unarmed; 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; distal and distoventral margins of pleomere VI sharply produced posterodorsally. Telson ( Fig. 5 c ) stout, smooth, about 3 times as long as wide proximally, slightly tapering distally, with 2 pairs of small dorsomarginal spines, each about 0.08 of telson length, inserted at about 0.35 and 0.5 telson length respectively; posterior margin slightly convex, with 4–5 pairs of distal spines.

Eyes ( Figs. 4 , 5 a, b ) small, partly reduced, swollen, subcylindrical ( Fig. 2 a, b ); cornea rounded, partly reduced and feebly marked, without pigment; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula ( Fig. 5 a, b ) with stout unarmed segments, basal peduncular segment robust, about 1.5 times longer than proximal width, without ventromedial tooth, distolateral angle with broadly produced sharp projection; stylocerite stout, sharp distally, overreaching the middle of basal segment; second and third segments unarmed, about as long as wide.

Antenna ( Fig. 5 a, b ) with 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 sharp distolateral tooth, lamella bluntly rounded distally.

Mouthparts characteristic for the genus, without specific features. Mandible 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 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 normal, with simple tapering small palp; endites stout, well-developed; basal endite feebly bilobed, furnished with elongated stiff setae; coxal endite obsolete; scaphognathite broad, furnished with short plumose setae. Maxilliped I normal; epipod small, reduced; exopodite 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 with relatively robust segments; without epipod; exopodite 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 with slender segments; epipod stout, bluntly rounded; arthrobranch present; exopodite 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, 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 ( Fig. 6 a, c ) equal in size and similar in shape, with relatively stouter segments, with smooth unarmed segments; coxa with well-developed slender epipodite and tuft of setobranchs; basis about as long as wide, with well-developed exopodite overreaching carpo-meral articulation; ischium about twice as long as wide, with straight margins; merus slender, about 2.5 times as long as wide, equal to carpus and 1.5 times longer than ischium, with straight margins; carpus relatively stout in females ( Fig. 6 a ) and slender in males ( Fig. 6 c ), widening distally, slightly longer than merus, about as long as maximal width in females and 1.5 times longer than maximal width in males; palm relatively stout, about as long as wide, subcylindrical in cross-section, smooth; fingers relatively stout, subcylindrical, smooth tapering distally, about 2 – 2.5 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 ( Fig. 6 b, d ) equal in size and similar in shape, similar in males and females, with smooth unarmed segments; coxa with well-developed slender epipodite and tuft of setobranchs; basis about 1.5 times as long as wide, with well-developed exopodite overreaching ischio-meral articulation, not reaching carpo-meral articulation; ischium about 2.5-3 times as long as wide, with straight margins; merus slender, about 4 times as long as wide, usually equal to ischium or lightly longer, with straight margins; carpus relatively slender, widening distally, slightly longer than merus, about 5–6 times longer than maximal width; palm relatively stout, similar to palm of pereiopod I, about as long as wide, subcylindrical in cross-section, smooth; fingers relatively stout, subcylindrical, smooth tapering distally, about 2 – 2.5 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.

Pereiopod III in females ( Fig. 6 e, f ) 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 exopodite almost reaching the midlength of merus; ischium about 2 times as long as wide, with well-marked ventral spine; merus about 7 times as long as wide, with straight margins, with 3 – 5 well marked spines along ventral margin; carpus relatively slender, about 3.5 – 4 times as long as wide, slightly widening distally, about half as long as merus and 1.5 times shorter than propodus, with bluntly projecting distodorsal margin slightly overlapping carpo-propodal articulation; propodus about 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. 7 a ) about 2 – 2.5 times as long as wide, biunguiculate, ventral margin armed with stout sharp triangular spines, main unguis smooth, curved and sharp; accessory unguis triangular, sharp, slightly larger than ventral spines, about twice shorter than main unguis. Pereiopod IV generally similar to pereiopod III; segments of pereiopod IV covered with simple setae dorsally and ventrally; merus armed with 3 – 4 ventral spines; carpus armed with single distoventral spine; propodus and dactylus similar to pereiopod III. Pereiopod V generally similar to pereiopods III and IV, but without armature on basal segments and exopodite on basis; propodus long and slender, about 8 times as long as wide, with 10 long slender spines along ventral margin and a pair of distoventral long slender spines; dactylus 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 males ( Fig. 6 g ) with relatively stout segments; coxa rectangular, about as long as wide, with tuft of setobranchs, with epipodite; basis about as long as wide, with well-marked exopodite almost reaching the midlength of merus; ischium about twice as long as wide, with well-marked ventral spine; merus about 7 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 half as long as merus and slightly longer than half of the length of propodus, with bluntly projecting distodorsal margin overlapping carpo-propodal articulation; propodus about 6 – 7 times as long as wide, with straight margins, armed with 4 – 5 spines along proximal half of ventral margin and dense row of small simple setae in distal half of ventral margin ( Fig. 7 b ); dactylus ( Fig. 4 b ) about 4 times longer than maximal wide, biunguiculate, ventral margin armed with dense row of small simple setae in its proximal half and with several stout sharp triangular spines in its distal half, main unguis smooth, curved and sharp; accessory unguis triangular, sharp, slightly larger than ventral spines, about twice shorter than main unguis, with well-marked dorsal lacinia. Pereiopod IV in males generally similar to pereiopod III; carpus unarmed. Pereiopod V in males generally similar to pereiopods III and IV, but without armature on basal segments and exopodite 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 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 endopodite ( Fig. 5 d ) reaching the half length of exopodite, subtriangular, with a well marked appendix interna near its distal margin. Endopodite of pleopod II in males ( Fig. 5 e ) with well-developed appendix interna and appendix masculina; appendix interna broad, tapering distally, covered with numerous small sharp spinules, without distal setae; appendix masculina slender, almost reaching the distal margin of appendix interna. Pleopods I and II in females normal, covered with small setae, characteristic for the genus without specific differentiating features.

Uropods relatively slender, slightly exceeding telson; lateral margin of uropodal exopodite straight, with sharp triangular distolateral angle and large curved distolateral spine.

Coloration. Body and appendages of shrimps are transparent whitish; cornea of eyes albescent; internal organs (gonads and hepatopancreas) are whitish or yellowish ( Fig. 8 ).

Measurements. The largest female has tl.— 30 mm, pcl.— 15 mm; the largest male has tl.— 20 mm, pcl.— 10 mm.

Remarks. The species is well distinguished from congeners by toothless rostrum with blunt tip (e.g. Fig. 4 ) according to short but informative original description given by Birštein (1969: Fig. 2 ). Besides the genetic data, the only informative morphological feature allowing separating species within the genus Хiphocaridinella is rostral length, although even this morphological feature is not always possible to apply (see Marin, 2017a). Anyway, Хiphocaridinella ablaskiri ( Birštein, 1939) is most closely morphologically similar to Хiphocaridinella jusbaschjani ( Birštein, 1948) also having blunt rostrum slightly not reaching the middle length of the basal antennular segment ( Marin & Sokolova, 2014: Fig. 2 a–c ) (vs. overreaching the midlength and usually reaching the distal margin of basal antennular segment in Х. ablaskiri ). Хiphocaridinella fagei ( Birštein, 1939) can be clearly separated from Х. ablaskiri by longer and distally thinning rostrum ( Marin & Sokolova, 2014: Fig. 14) and more slender distal segments of ambulatory pereiopods. Georgian species, Хiphocaridinella kutaissiana Sadowsky, 1930 and Хiphocaridinella kumistavi (Marin, 2017) , can be clearly separated from Х. ablaskiri by well-developed rostrum armed with dorsal and ventral teeth ( Marin & Sokolova, 2014: Fig. 12 ; Marin, 2017a).

Distribution. The species is known from underground streams of Otap Cave (=Golova Otapa) (42°55'19.3"N 41°32'19.6"E) (the type locality), two caves located higher up the slope—Uatapakhy (=Kolodez) (42°55'24.9"N 41°32'21.7"E) and Samshitovaya (42°55'32.8"N 41°32'26.0"E) caves, and neighboring Abrskil Cave (=Otapskaya, Achkshe-Tyz-Gua) (42°55'14.0"N 41°33'17.0"E). All these caves are situated near Otap village at Ochamchira District, Abkhazia, Western Caucasus. The caves are probably connected by underground stream representing the flow of several separate underground (subterranean) reservoirs inhabited by shrimps.

Figures

FIGURE 2. Phylogenetic UPGMA reconstrUction based on COI mtDNA gene marker of stUdied Western CaUcasian Xiphocaridinella species and Dinaric Troglocaris anophthalmus (Kollar, 1848) (FJ426022) as an oUtgroUp.

FIGURE 4. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella ablaskiri (Birštein, 1939) from Otap Cave (=Golova Otapa).

FIGURE 5. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella ablaskiri (Birštein, 1939) from Otap Cave (=Golova Otapa), female (a–c), male (d, e): a, b—front of carapace, dorsal view; c—telson; d—pleopod I; e—pleopod II.

FIGURE 6. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella ablaskiri (Birštein, 1939) from Otap Cave (=Golova Otapa), female (a, c, e, f), male (c, d, g): a, c—pereiopod I; b, d—pereiopod II; e—pereiopod III; f—pereiopod IV; g—pereiopod V.

FIGURE 7. Dactyli and distal part of propodUs of pereiopod III of troglobiotic shrimp Xiphocaridinella ablaskiri (Birštein, 1939) from Otap Cave (=Golova Otapa) in females (a) and males (b).

FIGURE 8. Alive coloration of troglobiotic shrimp Xiphocaridinella ablaskiri (Birštein, 1939) from Otap Cave (=Golova Otapa) (a, b) and Samshitovaya Cave (c, d): a–c—female, d, e—male ().

FIGURE 12. Alive coloration of troglobiotic shrimp Xiphocaridinella otapi sp. nov. from Otap Cave (=Golova Otapa), female (a–c), male (d, e).