Xiphocaridinella motena, Marin, 2019

Marin, Ivan, 2019, A new stygobiotic Xiphocaridinella (Crustacea: Decapoda: Atyidae) from the Motena Cave, Samegrelo-Zemo Svaneti region of Georgia, Caucasus, Zootaxa 4648 (3), pp. 592-600 : 594-599

Xiphocaridinella motena sp. nov.

( Figures 1 , 2 )

Type material. Holotype: Male (pcl. 6.5 mm, tl. 21.0 mm), ZMMU Ma 5836, Caucasus , GEORGIA, Samegrelo- Zemo Svaneti , Martvili Municipality , Balda village, Motena Cave, 42°28’35.3”N 42°23’28.4”E, about 471 m above the sea level, in subterranean lake, hand net sampling, coll. I. Marin, 13 Sept ľ2015 . 10 non-ovigerous females, 5 males ( LEMMI), same locality and date as holotype.

Description. Medium-sized shrimp with swollen subcylindrical body. Carapace ( Fig. 1 a–d) with small dorsal tubercle in frontal part and well developed supraorbital teeth ( Fig. 1d ). Rostrum ( Fig. 1 a–d) unarmed, relatively long, slender, lanceolate turned forward, reaching the distal margin of basal antennular segment, sharply pointed distally, with developed lateral lamina.

Abdominal somites smooth, unarmed; tergites non-carinate, without dorsal lobes, not posteriorly produced; pleura of pleomeres I–IV posteroventrally and ventrally rounded, distoventral margins of pleomere VI sharply produced posterodorsally. Telson ( Fig. 2k, l ) about 3 times as long as wide proximally, expanded distally, with 2 pairs of slender dorsal spines, inserted at about 0.25 and 0.5 telson length respectively; distal margin convex, with 3 pairs of distal spines.

Eyes ( Fig. 1 a–d) small, partly reduced, swollen, subcylindrical, partly covered by carapace; cornea rounded and feebly marked, without pigment; eyestalk stout, swollen, cylindrical, about as long as wide.

Antennula ( Fig. 1 e ) with robust basal peduncular segment, about twice longer than proximal width, without ventromedial tooth, distolateral angle with broadly produced sharp projection; stylocerite short, sharpening distally, not reaching the distal margin of basal segment; second and third segments stout, unarmed; second segment about 1.5 times as long as wide and about 1.5–2 times as long as distal segment; distal segment about as long as wide.

Antenna ( Fig. 1 f ) with basicerite stout, about 1.5 times as wide as 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. Maxilliped III ( Fig. 2 a ) slender, with small bluntly rounded epipodite and small; exopodite slender, almost reaching the distal margin of antepenultimate segment; antepenultimate segment slender, about 8 times as long as wide; penultimate segment about 7–8 times as long as wide, with straight lateral margins; ultimate (distal) segment slender, about 7 times as long as wide, tapering distally, with tufts of short simple stick-like setae along ventral and lateral margins.

Pereiopods I ( Fig. 2 b ) with basis about as long as wide, with well-developed exopodite overreaching carpomeral articulation; ischium about 3.5–4 times longer than wide; merus slender, about 3 times as long as wide, equal to ischium; carpus relatively stout in males and slightly more slender in females, significantly widening distally, slightly longer than merus, about as 1.5 times as long as maximal width; palm relatively stout, about as long as wide, subcylindrical in cross-section; fingers slender, subcylindrical, about 4 times as long as proximal width, armed with a row of stout strong plumose setae.

Pereiopods II ( Fig. 2 c ) with relatively stouter basal smooth unarmed segments; coxa with well-developed slen- der epipodite and tuft of setobranchs; basis about as long as wide, with well-developed exopodite overreaching carpo-meral articulation; ischium about 3 times as long as wide; merus slender, about 3 times as long as wide, usually equal to ischium or lightly longer; carpus slender, about 8 times as long as wide, slightly widening distally, longer than merus; palm relatively stout, similar to palm of pereiopod I, about as long as wide, subcylindrical in cross-section; fingers relatively slender, subcylindrical, smooth tapering distally, about 4 times as long as proximal width, with simple and straight cutting edge, with a row of strong plumose setae.

Pereiopod III in females ( Fig. 1 d, e ) with tuft of setobranchs and small 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 distoventral spine; merus about 7 times as long as wide, with 3 or 4 well-marked spines along ventral margin; carpus relatively slender, about 7 times as long as wide, slightly widening distally, about twice shorter than merus and propodus, with small subdistal spine; propodus about 10 times as long as wide, with straight margins, armed with 7–8 spines along proximal half of ventral margin; dactylus ( Fig. 1 f, g ) about 3 times longer than wide, biunguiculate; ventral margin in females ( Fig. 1 g ) armed with 5–6 small spines, main unguis smooth, curved and sharp; accessory unguis sharp, slightly larger than ventral teeth, about twice shorter than main unguis; ventral margin in males ( Fig. 1 f ) armed with a row of small ventral spines, main unguis smooth, curved and sharp; accessory unguis sharp, slightly larger than ventral teeth.

Pereiopod IV generally similar to pereiopod III; merus armed with 3 spines, carpus armed with single spine; exopodite smaller than in pereiopod III. Pereiopod V in females 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 long spines along ventral margin and pair of long slender 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.

Pleopod I in with endopod bearing well marked appendix interna. Pleopod II in males ( Fig. 1 g ) with well-developed appendix interna and appendix masculina; appendix masculina covered with numerous small sharp stout simple spines. Pleopods I and II in females normal, characteristic for the genus without specific differentiating features.

Uropods ( Fig. 1 h ) relatively stout, slightly exceeding telson; lateral margin of uropodal exopodite straight, with sharp triangular distolateral angle and 1 or 2 large curved distolateral spines ( Fig. 1 i, j ); dieresis simple, without spines.

Coloration. Body and appendages of shrimps are translucent white or yellowish in color; cornea of eyes is albescent; internal organs (gonads and hepatopancreas) are whitish or yellowish ( Fig. 4 ).

Body size. The largest collected female has tbl. 6.5 mm, pcl. 21.0 mm; the largest collected male has tbl. 6.0 mm, pcl. 20.0 mm.

Etymology. The species is named after the Motena Cave (42°28’35.3”N 42°23’28.4”E), where it was found.

GenBank accession numbers. MN 105981 , MN 105982 .

Distribution. The species is known from the type locality—an underground lake inside the Motena Cave (42°28’35.3”N 42°23’28.4”E), Martvili Municipality, Samegrelo-Zemo Svaneti, Western Georgia, Caucasus.

Taxonomic remarks. The new species distinctly belongs to the Western Georgian (“ kutaissiana ”) group of Xiphocaridinella species ( Fig. 3 ; Table 2 ). The known species of this group, namely X. kutaissiana and X. kumistavi , have long fingers of pereiopods I and II in both males and females, which clearly distinguish them from the Caucasian relatives. At the same time, the new species can be distinguished from the latter species by specific short and unarmed lanceolate unarmed rostrum, turned forward ( Fig. 2 a–d), showing the quite unique form within the genus. In both of the latter species, rostrum in most of the studied individuals is long, overreaching the distal margin of basal antennular segment, and armed with dorsal and ventral teeth (see Marin, 2017a: Figs.1-4 ). However, some specimens (see Marin, 2017a: Fig. 4 b, d, f ) show similar lanceolate unarmed rostrum that satisfy the relationship between these species. At the same time, individuals with armed rostrum were not found in the population of Xiphocaridinella motena sp. nov. from the Motena Cave.

Figures

FIGURE 1. Xiphocaridinella motena sp. nov., Motena Cave, Western Georgia, female (a, b, i, k), male (c–h, j, l): a–d—front of carapace; e—antennula; f—antenna; g—pleopod II with appendix interna and appendix masculine; h—uropods; i, j—same, distolateral angle of exopod; k, l—telson.

FIGURE 2. Xiphocaridinella motena sp. nov., Motena Cave, Western Georgia, male (a–c, e, f), female (d, g): a—maxilliped III, b—pereiopod I; c—pereiopod II; d, e—pereiopod III; f, g—dactylus of pereiopod III.

FIGURE 3. Phylogenetic (COI mtDNA) reconstruction (tree) of the Caucasian Xiphocaridinella with BA/ML/NJ (upper) and UPGMA (lower) algorithm.

FIGURE 4. The entrance of Motena Cave and subterranean lake inside it with enlarged photo of Xiphocaridinella motena sp. nov. Photocredits: R. Borisov (cave lake).