Xiphocaridinella otapi, Marin, 2018

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 : 213-219

Xiphocaridinella otapi sp. nov.

( Figs. 9–12 )

Material examined. Holotype, male, ZMMU Ma 3573, 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, 25 August 2015; 10 non-ovigerous females, 5 males, collected at the same locality in Otap Cave; 18 non-ovigerous females , 8 males, Western Caucasus, Abkhazia, Ochamchira District, Otap village , 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 and puddles, hand net sampling, coll. I. Marin & I. Turbanov, 25–26 August 2015 .

Description. Medium-sized shrimp with swollen, smooth, subcylindrical body. Males are similar in size and morphology to females ( Fig. 12 ). Carapace ( Fig. 9 ) swollen, smooth, with small blunt dorsal knob, without dorsal or lateral carina, covered with small simple setae; rostrum ( Figs. 9 , 10 a–e ) slender, facing forward, reaching midlength of second antennular segment, subulate, thin distally and broad in its proximal part, with feebly marked lateral lamina proximally, dorsally and ventrally unarmed.

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. 10 g ) stout, smooth, about 3.5 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 0.4 and 0.6 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 ( Fig. 10 h ).

Eyes ( Fig. 9 , 10 a–e ) small, partly reduced, swollen, subcylindrical, only proximal part concealed with carapace and lateral rostral carina ( Fig. 2 a, b ); cornea rounded, partly reduced and feebly marked, without pigment; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula ( Fig. 10 i ) 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 midlength of basal segment; second and third segments stout, unarmed, about as long as wide.

Antenna 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.

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 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 equal in size and similar in shape, with smooth unarmed relatively stouter distal segments in females ( Fig. 11 a ) and slender segments in males ( Fig. 11 h ); 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 1.5 – 2 times as long as wide, with straight margins; merus relatively stout, about 2.5 – 3 times as long as wide, slightly longer than ischium, with straight margins; carpus widening distally, relatively stout, about as long as maximal width, in females ( Fig. 11 a ) and relatively slender, about twice longer than maximal width, in males ( Fig. 11 h ); palm stout, 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 in males ( Fig. 11 b ) and females ( Fig. 11 g ), 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 1.5 times as long as wide, with straight margins; merus about 2.5 – 3 times as long as wide, usually slightly longer than ischium, with straight margins; carpus widening distally, shorter, about 3 times longer than maximal width, in females ( Fig. 11 b ) and relatively long, about 6.5 – 7 times as long as its maximal width, in males ( Fig. 11 g ); palm 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 twice as long as wide in females, and about 3 times as long as wide in males, 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. 11 c ) with 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 1.5 – 2 times as long as wide, with well-marked ventral spine; merus about 4 – 5 times as long as wide, with straight margins, with 3 – 4 well marked spines along ventral margin; carpus relatively slender, about 5 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; dactylus ( Fig. 11 f ) about 2.5 – 3 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 ( Fig. 11 d ) 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 ( Fig. 11 e ) 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 small spines along ventral margin and a pair of distoventral spines; dactylus ( Fig. 12 c ) 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 ( Figs. 11 i ) 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 2.5 – 3 times 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 5 – 6 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. 11 j ); dactylus ( Fig. 11 j ) about 5 times as long as 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. 5d ) reaching the half length of exopodite, subtriangular, with a well marked appendix interna near its distal margin. Endopodite of pleopod II in males ( Fig. 10 j ) with well-developed appendix interna and appendix masculina; appendix interna broad, tapering distally, covered with numerous small sharp spinules, without distal setae; appendix masculina ( Fig. 10 k ) 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 ( Fig. 10 f ) relatively stout, slightly exceeding telson; lateral margin of uropodal exopodite straight, with sharp triangular distolateral angle and large curved distolateral spine; dieresis simple.

Measurements. The largest female has tl.— 32 mm, pcl.— 17 mm; the largest male has tl.— 23 mm, pcl.— 13 mm.

Coloration. Body and appendages of shrimps are transparent whitish; cornea of eyes albescent; internal organs (gonads and hepatopancreas) are whitish or yellowish ( Fig. 12 ).

Etymology. The species is named after Otap Cave (=Golova Otapa), 42°55'19.3"N 41°32'19.6"E, where it was firstly found.

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) and Abrskil Cave (=Otapskaya, Achkshe-Tyz-Gua) (42°55'14.0"N 41°33'17.0"E) situated near Otap village at Ochamchira District, Abkhazia, Western Caucasus. It is obvious that both caves are connected through the same underground streams as considered Хiphocaridinella species were found both in Otap and Abrskil caves. At the same time, we can suggest that streams inside caves are forming by flows from separate subterranean water reservoirs (subterranean lakes) inhabited by just a single Хiphocaridinella species.

Taxonomical remarks. The examined adult specimens show some variation in rostral length (see Figs. 9 , 10 a–e ). Rostrum of Хiphocaridinella otapi sp. nov. is significantly longer, reaching the middle of the second antennular segment, subulate, broad in its proximal part and thinning distally while rostrum is small and triangular, not reaching distal margin of basal antennular segment, with bluntly pointed and slightly curved upward tip in Х. ablaskiri (see Fig. 4 ). The other small morphological differences between two species are (1) the length of carpus of pereiopod I and II; (2) position of dorsal pines on telson and the presence of small supraocular spines on carapace of some specimens of Х. ablaskiri , while they were never observed in Хiphocaridinella otapi sp. nov. The significant genetic difference between species (more than 8%) in a case of their syntopic co-occurrence also suggest to consider them as separate biological species (see above).

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 9. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella otapi sp. nov. 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 10. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella otapi sp. nov. 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 11. RostrUm and front of carapace of troglobiotic shrimp Xiphocaridinella otapi sp. nov. 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 12. Alive coloration of troglobiotic shrimp Xiphocaridinella otapi sp. nov. from Otap Cave (=Golova Otapa), female (a–c), male (d, e).