Xiphocaridinella lechkhumensis, Marin & Barjadze, 2022

Marin, I. N. & Barjadze, Sh., 2022, A new species of stygobiotic atyid shrimps of the genus Xiphocaridinella (Crustacea: Decapoda: Atyidae) from the Racha-Lechkhumi and Kvemo Svaneti, with a new record of X. kumistavi from the Imereti, Western Georgia, Caucasus, Invertebrate Zoology 19 (1), pp. 24-34 : 27-31

Genus Xiphocaridinella Sadowsky, 1930 Xiphocaridinella lechkhumensis sp.n.

Fig. 2 .

TYPE MATERIAL. HOLOTYPE, non-ovigerous ♀ (pcl. 4.2 mm, tbl. 14.0 mm) (damaged, without pereopods), ZMMU Ma-6215, SW Caucasus, Georgia, Racha-Lechkhumi and Kvemo Svaneti, Tsageri Municipality, inside Verdzistava II Cave located near the village of Tvishi , 42°31′44.23″N 42°47′38.79″E, about 400 m a.s.l., coll. G. Nebieridze, 16.05.2018.

PARATYPE, 1 juv. (pcl. 3.8 mm, tbl. 12.0 mm) (damaged), IZISU AC-T-00001 , same locality and data as holotype .

ETYMOLOGY. The new species is named after Lechkhumi region of the Western Georgia, where it was discovered.

DESCRIPTION. Small-sized shrimp with swollen, subcylindrical body.

CARAPACE ( Fig. 2A–C, E ) smooth, dorsally unarmed. ROSTRUM ( Fig. 2A–C, E ) dorsoventrally flattened, broadly triangular in dorsal view, distally slightly upturned in holotype ( Fig. 2 A, B ), straight in paratype ( Fig. 2C, E ); dorsal surface unarmed, but

with short carina in distal half; lateral margins slightly convex or straight, each with small tooth located at about midlength; ventral surface unarmed.

EYES ( Fig. 2A–C, E ) reduced, without pigment; eyestalk stout, swollen, subcylindrical, about as long as wide.

PLEON (not illustrated) smooth, unarmed; tergites non-carinate; pleura of pleomeres I–IV marginally rounded, posteroventral margins of pleomere V slightly produced posterodorsally. Telson ( Fig. 2I ) about 3.7 times as long as proximal width, tapering distally, with 2 pairs of small dorsal submarginal spines, set at about 0.45 and 0.75 telson length respectively; distal margin almost straight, with 4 pairs of spines.

ANTENNULE ( Fig. 2F, G ) with robust basal peduncular segment, about twice longer than proximal width, without ventromedial tooth, distolateral angle with broadly produced; stylocerite tapering distally to acute tip, reaching beyond mid-length of basal peduncular segment; second and third peduncular segments stout,unarmed; second segment about 1.8 times as long as wide and about 1.5–2 times as long as distal segment; distal segment about as long as wide; flagellum well developed, about as long as body length.

ANTENNA ( Fig. 2H ) with basicerite stout, with ventrolateral distal spine; carpocerite robust, about 2 times as long as wide, reaching midlength of scaphocerite; scaphocerite well developed, broad, with small but well-marked distolateral tooth not reaching to rounded distal margin of lamella.

MOUTHPARTS typical for the genus, without specific features, not figured. 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. Maxillule with dorsal lobe bearing completely fused lacinia, ventral lobe small, covered with curved setae distally, palp well-developed, with 2 distal setae. Maxilla with small, tapering palp; endites moderately broad, well developed; basal endite feebly bilobed, furnished with elongated stiff setae; coxal endite obsolete; scaphognathite broad, furnished with short plumose setae. Maxilliped I with reduced epipod; exopod small and slender, basally with expanded caridean lobe bearing plumose marginal setae; basal and coxal endites completely fused, excavate, furnished with long simple setae distally. Maxilliped II without epipod; exopod long and slender, reaching distal segments. Maxilliped III slender, with small epipod on coxa bearing feebly developed terminal hook interacting setobranch on pereopod I, and with arthrobranch; exopod slender, almost reaching distal margin of antepenultimate segment; antepenultimate segment slen- der, about 8 times as long as wide; penultimate segment about 7–8 times as long as wide, with straight lateral margin; 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.

PEREOPOD I (present in paratype only) ( Fig. 2M ) stout; coxa with well-developed slender epipod bearing feebly developed terminal hook and setobranch; basis about as long as wide, with feebly developed exopod (not illustrated); ischium about 1.5 times longer than wide; merus stout, about 1.5– 2 times as long as wide, slightly longer than ischium and equal in length to carpus; carpus relatively stout, significantly widening distally, about as long as maximal width; palm stout, about 1.3 times as long as wide,subcylindrical in cross-section;fingers stout, about 1.5 times as long as the length of palm and about 1.3–1.5 times as long as their proximal width, blunt distally, armed with a row of stout strong plumose setae fringing terminal margins.

PEREOPOD II (present in paratype only) ( Fig. 2N–P ) stout, subequal in length to pereopod I; coxa with epipod and setobranchs; basis about as long as wide, with short exopod, probably because of feebly development in the juvenile specimen; ischium about 1.5 times as long as wide; merus slender, about 2 times as long as wide, slightly longer than ischium; carpus relatively slender, about 1.3 times as long as wide, widening distally; palm ( Fig. 2P ) stout, similar to that of pereopod I, about as long as wide, subcylindrical in cross-section; fingers stout, about 1.5 times as long as palm, blunt distally, about as long as proximal width, with simple and straight cutting edge, with row of strong plumose setae on terminal margins.

PEREOPOD III ( Fig. 2J ) relatively slender; coxa with setobranch and small epipod without terminal hook; basis about as long as wide, with well-developed exopod overreaching mero-carpal articulation ischium about 2.0–2.5 times as long as wide, with 1 subdistal small movable spine on lateral surface ventrally; merus about 6 times as long as wide, with 3 spines on lateral surface along ventral margin; carpus relatively slender, about 7 times as long as wide, slightly widening distally, about half-length of merus or propodus, with small subdistal spine on lateral surface; propodus straight, about 10 times as long as wide, armed with 9 spinules on proximal half of flexor margin and a row of short simple setae on its distal half; dactylus about 2.5–3 times longer than maximal width, biunguiculate, flexor margin armed 2 accessory spinules on the flexor margin in addition to the penultimate unguis and several small simple setae, ultimate unguis smooth, curved; penultimate unguis triangular, sharp, larger than other accessory spines on flexor margin, about half-length of ultimate unguis.

PEREOPOD IV ( Fig. 2K ) generally similar and slightly shorter than pereopod III; coxa with tuft of setobranchs and small epipod; basis about as long as wide, with well-developed exopod overreaching carpo-meral articulation; ischium about 1.7 times as long as wide, with small distoventral movable spine; merus about 6 times as long as wide, armed with 3 spines on lateral surface along ventral margin; carpus about 5 times as long as wide with small subdistal spine on lateral surface; propodus about 8 times as long as wide, with straight margins, armed with 7 spinules along ventral margin; dactylus about 2.5–3 times longer than wide, biunguiculate; flexor margin armed with 2 small accessory spinules in addition to the penultimate unguis, ultimate unguis smooth, curved and sharp, penultimate unguis sharp, about twice larger than ventral teeth, about twice shorter than ultimate unguis.

PEREOPOD V ( Fig. 2L ) similar to pereopods III and IV; basis without exopod; propodus about 10 times as long as wide, with straight margins, ventrally unarmed; dactylus with ventral margin armed with a dense “brush” consisting of small simple sharp setae; without penultimate and accessory unguis, ultimate unguis curved, triangular, sharp distally.

PLEOPODS without specific differentiating features.

UROPODS (Fig. 4I) relatively slender, slightly exceeding telson; lateral margin of exopod straight, with 1 large spine mesial to posterolateral tooth; dieresis simple, unarmed.

COLORATION IN LIFE. Body and appendages translucent white; cornea of eye albescent.

GENBANK ACCESSION NUMBERS. OL704738 (holotype), OL704739 (paratype) .

DISTRIBUTION.The species is currently known only from the type locality — Verdzistava II Cave.

TAXONOMIC REMARKS. The new species belongs to the genetically and geographically separated “ kutaissiana ” group (clade) in Xiphocaridinella distributed in Western Georgia (see Fig. 1 ), including X. kutaissiana Sadowsky, 1930 (the type species of the genus) from the Tskal-Tsiteli (=Iazoni) Cave, Kutaisi (see Sadowsky, 1930; Marin, Sokolova, 2014), X. kumistavi (Marin, 2017) from the Prometheus Cave, Imereti region (see Marin, 2017) and X. motena Marin, 2019 from the Motena Cave, Samegrelo-Zemo Svaneti region (see Marin, 2018b, 2019). However, X. lechkhumensis sp.n. is unique in the “ kutaissiana ” group by the relatively short rostrum, not reaching the midlength of the basal segment of the antennular peduncle (see Fig. 2A, B ), while other species of the group have rostrum distinctly overreaching the distal margin of the basal segment of the antennular peduncle. The unarmed rostrum is shared only with X. motena , whereas in X. kutaissiana and X. kumistavi the rostrum is dorsally and ventrally armed. We have only two individuals, probably both immature, but the rostrum is still much smaller than that of immature individuals in other species of the group.

The new species can be easily separated genetically from the species of the “ kutaissiana ” species group, as well as other congeners (see Fig. 1 ; Table 1). The minimum genetic divergence of COI between other Caucasian congeners is 8%, which supports the validity of the new species.

Currently, Khvampli karst massif is located in Lechkhumi historic region of Western Georgia ( Tatashidze et al., 2009), where cave dwelling invertebrates are poorly investigated. Only two species are recorded in this karst massif: collembolans Argonychiurus multiocellatus Djanashvili, Barjadze, Jordana et Burkhardt, 2014 (Colembola: Onychiuridae ) (troglobiont) and Plutomurus birsteini Djanashvili et Barjadze, 2011 (Colembola: Tomoceridae ) (troglophile) ( Djanashvili,Barjadze, 2011; Djanashvili et al., 2014). Both of them are living in the Tvishi Cave.

Figures

Fig. 2. Xiphocaridinella lechkhumensis sp.n., holotype, ♀, pcl. 5.0 mm, tl. 16.0 mm, ZMMU Ma-6215 (A, B, F–P); paratype ♀, pcl.3.2 mm, tl. 12.0 mm, IZISUAC-T-00001 (C–E):A, C, E — front of carapace,dorsal view; B, D — front of carapace, lateral view; F — antennula, dorsal view; G — antennula, lateral view; H — antenna; I — telson and uropods, dorsal view; J — pereopod III; K — pereopod IV; L — pereopod V; M — pereopod I; N, O — pereopod II, different views; P — chela of pereopod II, ventral view. Рис. 2. Xiphocaridinella lechkhumensis sp.n., голотип, ♀, pcl. 5,0 мм, tl. 16,0 мм, ZMMU Ma-6215 (A, B, F–P); паратип, ♀, pcl. 3,2 мм, tl. 12,0 мм, IZISU AC-T-00001 (C–E): A, C, E — переднЯЯ часть карапаскса, вид сверху; B, D — переднЯЯ часть карапакса, вид сбоку; F — антеннула, вид сверху; G — антеннула, вид сбоку; H — антенна; I — тельсон и уроподы, вид сверху; J — переопод III; K — переопод IV; L — переопод V; M — переопод I; N, O — переопод II, раЗные виды; P — клеШнЯ переоподы II, вид сниЗу.

Fig. 1. The map indicating the locality, where shrimps where collected (A), and phylogenetic reconstruction (tree) of the Caucasian species of Xiphocaridinella (GTR+G+I model) (below) using mitochondrial COI mtDNA gen marker with the support (BS) based on ML method (B). Рис. 1. Карта сукаЗанием района, где были собраны креветки (А), и филогенетическаЯ реконструкциЯ (дерево) КавкаЗских Xiphocaridinella (модель GTR+G+I) (ниже) c испольЗованием генного маркера COI мтДНК) с поддержкой на основе метода ML (Б).