Niphargus rachalechkhumensis, Marin & Barjadze & Maghradze & Palatov, 2023

Marin, Ivan, Barjadze, Shalva, Maghradze, Eter & Palatov, Dmitry, 2023, Diversity, taxonomy and phylogenetic relationships of the “ Niphargus borutzkyi ” ingroup (Crustacea: Amphipoda: Niphargidae) in Western Georgia, SW Caucasus, Zootaxa 5352 (4), pp. 477-500 : 481-483

publication ID	https://doi.org/ 10.11646/zootaxa.5352.4.2
publication LSID	lsid:zoobank.org:pub:4497FA6F-FB5D-475A-90A0-24BA499D3D4A
DOI	https://doi.org/10.5281/zenodo.8426510
persistent identifier	https://treatment.plazi.org/id/03BD927D-FFB1-FFB0-FF1A-5291FD18F8D4
treatment provided by	Plazi
scientific name	Niphargus rachalechkhumensis
status	sp. nov.

Treatment

Niphargus rachalechkhumensis sp. nov.

Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 10 a, b View FIGURE 10 , 11 e View FIGURE 11

Material examined. Holotype: ³ (bl. 14.5 mm), ZMMU Mb-1245—SW Caucasus, Western Georgia, Racha-Lechkhumi and Kvemo Svaneti, Sakishore Cave , 42°26’31.8”N 43°09’34.4”E, 1189 m a.s.l., in subterranean stream, 12 xi.2020, coll. E. Maghradze & Sh. Barjadze. GoogleMaps

Paratypes: 1 ³, ZMMU Mb-1246, and 1³ (bl. 10 mm), 1♀ (bl. 13 mm) , IZISU,— Sakishore Cave , 42°26’31.8”N 43°09’34.4”E, 1189 m a.s.l., in subterranean stream, 14 viii.2019, collected by international expedition GoogleMaps .

Additional material: SW Caucasus, Western Georgia, Racha-Lechkhumi and Kvemo Svaneti: 2³³, 4♀♀, LEMMI — Dolabistavi Cave , 42°27’03.9”N 43°10’39.5”E, 1187 m a.s.l., in subterranean stream, 14 viii.2019 GoogleMaps , collected by international expedition; 2♀♀, LEMMI — Tsageri Municipality, on the slope of the Rioni river near Tvishi village , Verdzistava II Cave , 42°31’44.23”N 42°47’38.79”E, about 400 m a.s.l., subterranean stream in dark zone, 10 vi.2021, coll. E. Maghradze, Sh. Barjadze, M. Gogshelidze & N. Modebadze. GoogleMaps

Etymology. The species is named after the Racha-Lechkhumi and Kvemo Svaneti, Western Georgia, where it was discovered in several caves.

Diagnosis. Urosomite II with 3 stout dorsoposterior spine-like setae on each side. Epimeral plates I and II subangular, with rounded posteroventral corner, epimeral plate III with bluntly produced posteroventral corner. Gnathopods I–II moderate, almost similar in size, palm almost rectangular, with straight distal margin, dactylus with a row of several setae along outer margin. Dactyli of pereopods III–VII with 1 spine or seta near basis of nail. Pleopods with 6 – 7 hooks in retinacules, without additional setae. Uropod III elongated, article 2 of outer ramus long, article 1 (distal) about 5 times shorter than article 2 in females, and almost equal to article 2 in males. Telson relatively stout, deeply incised, each lobe with 4–5 long distal spines and 2 outer marginal spines, facial spines absent.

Description. Body medium in size, moderately slender.

Head without rostrum, with subrounded lateral cephalic lobes and excavated anteroventral sinus; eyes or pigmented spots absent ( Fig. 10 b View FIGURE 10 ).

Epimeral plates I and II subangular, with rounded posteroventral corner, epimeral plate III with bluntly produced posteroventral corner; ventral margin of epimeral plates II and III armed with 4–5 small simple spines ( Fig. 5 a–c View FIGURE 5 ).

Urosomite I armed with 2 slender dorsoposterior setae on each side; urosomite II with 3 stout dorsoposterior spine-like setae on each side; urosomite III unarmed ( Fig. 10 a View FIGURE 10 ).

Coxal gills ovoid, of moderate size, reaching and overreaching distal tip of article 2 of ambulatory pereopods.

Antenna I ( Fig. 2 a View FIGURE 2 ) slender, long; peduncular articles moderately slender, ratio 1:0.83:0.45; flagellum consisting of about 29 articles, most of them with 2 short aesthetascs each; accessory flagellum ( Fig. 2 b View FIGURE 2 ) short, 2-articulated.

Antenna II ( Fig. 2 c View FIGURE 2 ) with peduncular article 3 almost equal to article 2, about 5 times as long as wide, with separate rare tufts of long setae along distoventral margin; article 2 about 4.5 times as long as wide; article 1 about as long as wide; flagellum relatively short, consisting of about 15 articles bearing relatively short setae.

Mouthparts. Labium ( Fig. 3 a View FIGURE 3 ) entire, with convex dorsal margin, covered with tiny setae. Labrum ( Fig. 3 b View FIGURE 3 ) entire, slightly broader than long, with entire outer lobes and developed inner lobes exceeding half of outer lobes. Mandibles ( Fig. 3 c–f View FIGURE 3 ) with mandibular palp ( Figs 3c, e View FIGURE 3 ; 10 f View FIGURE 10 ) consisting of 3 articles: article 1 about 1.5 times as long as wide, smooth; article 2 about 2.5 times as long as wide, with numerous setae, article 3 subfalciform, about 3.5 times as long as wide, slightly shorter than article 2, with group of 7 A-setae; 3 groups of B-setae; 24 D-setae and 6 E-setae. Maxilla I ( Fig. 3 g View FIGURE 3 ) with: inner plate with relatively short 2–3 long distal simple setae, outer plate with 7 robust spines armed with 1small lateral teeth each, the lowest spine with several tiny teeth ( Fig. 3 h View FIGURE 3 ); palp 2-articulated, distal article with a tuft of long simple setae distally. Maxilla II ( Fig. 3 i View FIGURE 3 ) with smooth well-developed lobes armed with numerous distolateral setae, distal margins with long simple setae. Maxilliped ( Fig. 3 j View FIGURE 3 ) with short inner plate armed with 3 distal simple strong spines; outer plate reaching half of palp article 2, with row of inner strong lateral spines; palp 4-articulated, distal article with large spine.

Gnathopods moderate, similar in size, with article 6 slightly smaller than corresponding coxae ( Fig. 2 d, f View FIGURE 2 ).

Gnathopod I ( Fig. 2 d View FIGURE 2 ) with basis robust, about 3 times as long as wide, with long simple setae along posterior and posterodistal margins; ischium almost quadrate, as long as wide, similar to merus; merus quadrate, about as long as wide, with row of long setae along posterior margin; carpus mostly rectangular in shape, about 1.5 times as long as wide; propodus large, nearly as long as broad, trapezoid, with several (9–10) groups of ventral marginal setae; propodus (chela) with palmar margin poorly convex, almost straight, with medium simple setae, defined on outer face by one strong large corner spine accompanied laterally by 3 stout distally serrated robust spine spines ( Fig. 2 e View FIGURE 2 ); dactylus strong and sharp, reaching posterior margin of propodus, with a row of small numerous setae along dorsal margin.

Gnathopod II ( Fig. 2 f View FIGURE 2 ) with basis relatively slender, about 4 times as long as wide, with long simple setae along posterior and posterodistal margins; ischium almost about as long as wide, similar to merus; merus subquadrate, about 1.5 times as long as wide, with row of long setae along posterior margin; carpus trapezoid in shape, about 2 times as long as wide; propodus (chela) large, nearly as long as broad, trapezoid, with numerous groups of ventral marginal setae; propodus (chela) with palmar margin poorly convex, almost straight, with medium simple setae, defined on outer face by one strong large corner spine accompanied laterally by 3 stout distally serrated robust spine spines ( Fig. 2 g View FIGURE 2 ); dactylus strong and sharp, reaching posterior margin of propodus, with a row of small numerus setae along dorsal margin.

Pereopods III–IV ( Fig. 4 a, c View FIGURE 4 ) almost similar in size and shape; basis about 5 times as long as wide, with margins armed with long setae; ischium short, about as long as wide; merus about 3.5 times as long as wide, with simple setae along dorsal and ventral margins; carpus shorter than propodus, about 3–3.5 times as long as wide; propodus about 6 times as long as wide, with small simple spines along ventral margin; dactylus ( Fig. 4 b, d View FIGURE 4 ) relatively slender, curved, sharp distally, with small ventral median spine.

Pereopods V–VI ( Fig. 4 e, g View FIGURE 4 ) with basis almost subrectangular, about 2 times as long as wide, slightly widening proximally, without posteroventral lobe, anterior margin of basis slightly convex, with a row of slender marginal setae that slightly longer than posterior; ischium small, subquadrate, as long as wide; merus about 4 times as long as wide, with short setae along dorsal and ventral margins; carpus robust, about 4–4.5 times as long as wide, almost equal to merus; propodus relatively slender, about 6–6.5 times as long as wide, armed with short simple spines; dactylus slender, curved, sharp distally, with additional ventral median spine ( Fig. 4 f, h View FIGURE 4 ).

Pereopod VII ( Fig. 4 i View FIGURE 4 ) moderately slender, with basis narrowly rectangular, about 2.5 times as long as broad, anterior and posterior margins slightly convex; ischium small and short, as long as wide; merus about 2.5 times as long as wide, with short spines along dorsal and ventral margins; carpus about 4–4.5 times as long as wide, shorter than propodus, armed with simple setae; propodus slender, about 7 times as long as wide, armed with small single setae along margins; dactylus slender, curved, sharp distally, with additional ventral median spine, sometimes with the second additional spine in the middle of main (basal) part ( Fig. 4 j View FIGURE 4 ).

Pleopods with 6–7 hooks in retinacules, without additional setae ( Figs 5 g View FIGURE 5 , 11 e View FIGURE 11 ).

Uropod I ( Fig. 5 h, i View FIGURE 5 ) with protopodite (peduncle) about 4 times as long as wide, slightly longer than rami, with a dorsoexternal row of slender simple spines; rami about 5 times as long as wide, equal in length, armed with armed with lateral and distal relatively robust simple spines.

Uropod II ( Fig. 5 j, k View FIGURE 5 ) with protopodite (peduncle) about 3–3.5 times as long as wide, equal to rami; rami almost equal in size, with lateral and distal slender spines.

Uropod III ( Fig. 5 l, m View FIGURE 5 ) different in males and females. Uropod III in females ( Fig. 5 l View FIGURE 5 ) with protopodite about 1.5 times as long as wide, rami unequal, inner ramus short, about 6–6.5 times shorter than outer one, bearing several small distal and lateral spines; outer ramus long, proximal article about 6–6.5 times as long as wide, distal article about 5 times shorter than previous article, about 3.5–4 times as long as wide, with several small distal simple setae. Uropod III in males ( Fig. 5 m View FIGURE 5 ) with protopodite about 1.5 times as long as wide, rami unequal, inner ramus short, about 10–10.5 times shorter than outer one, bearing several small distal and lateral spines; outer ramus long, proximal article about 11 times as long as wide, distal article about 1.2 times shorter than previous article, about 12–13 times as long as wide, with several small distal simple setae.

Telson ( Fig. 5 d, e View FIGURE 5 ) about 1.3 times longer than broad, ca. 85% incised, lobes obtuse and sloping distally. Armature of telson is variable, bearing 4–6 long distal spines, and 2 outer marginal spine-like setae on each side; distal and marginal spines relatively long and slender, reaching about 0.5 of length of telson.

Body size. The largest collected female has bl. 12.5 mm; the largest male has bl. 14.5 mm.

GenBank accession number. MW014293–MW014296.

Taxonomic remarks. From mostly related N. borutzkyi , the new species can be separated by (1) the presence of 3 stout dorsoposterior spine-like setae on urosomite II ( Fig. 10 a View FIGURE 10 ) vs. always 4 slender spine-like setae ( Marin 2020: Fig. 8 b View FIGURE 8 ); (2) significantly shorter distal segment of uropod III in females, which is more than 5 times shorter than the previous segment ( Fig. 5 l View FIGURE 5 ) vs. about 4 times as long as wide ( Marin 2020: Fig. 7 e View FIGURE 7 ); (3) bluntly produced posteroventral angle of epimeral plate III ( Fig. 5 c View FIGURE 5 ) vs. non produced, mostly rectangular angle ( Birštein 1933: Abb. 7).

From N. amirani , the new species can be clearly separated by (1) 3 stouter and shorter dorsoposterior spine-like setae on urosomite II ( Fig. 10 d View FIGURE 10 ) vs. always 3 significantly slender spine-like setae ( Marin 2020: Fig. 8 b View FIGURE 8 ); (2) shorter distal segment of uropod III in females, which is more than 5 times shorter than the previous segment ( Fig. 5 m View FIGURE 5 ) vs. about 3 times as long as wide ( Marin 2020: Fig. 7 e View FIGURE 7 ).

Ecology and distribution. Niphargus rachalechkhumensis sp. nov. is presently known from two neighboring Rachian (Sakishore and Dolabistavi) and one Lechkhumian (Verdzistava II) caves; probably, these caves are connected by a single underground water stream, since the same stygobiotic species inhabits them all (e.g., Marin & Turbanov 2021). The eleven invertebrate species are known from the Sakishore Cave, of which only five species are troglomorphic: Dina ratschaensis Kobakhidze 1958 (leech), Leucogeorgia longipes Verhoeff, 1930 (millipede), Inotrechus injaevae Dolzhanskij et Ljovuschkin, 1989 (beetle), Nemaspela femorecurvata Martens, 2006 (harvestman), and Sitnikovia ratschuli Chertoprud, Palatov, Vinarski, 2020 (mollusk) ( Barjadze et al. 2019a, b; Antić & Reip 2020; Chertoprud et al. 2020). Seven invertebrates with three troglomorphic species, namely Hausdorfenia pseudohauffenia Grego & Mumladze, 2020 (mollusk), Leucogeorgia longipes Verhoeff, 1930 (millipede) and Neobisium sp. (pseudoscorpion), have been recorded from the Dolabistavi Cave ( Barjadze et al. 2019a, b; Grego et al. 2020). Only stygobiotic shrimp Xiphocaridinella lechkhumensis Marin & Barjadze, 2022 is know from the Verdzistava II Cave ( Marin & Barjadze 2022).