Niphargus tvishiensis, 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 : 488-496

Niphargus tvishiensis sp. nov.

Figs 6–9 , 10 c–f , 11 f

Material examined. Holotype: ³ (bl. 15.0 mm), ZMMU Mb-1247—SW Caucasus, Western Georgia, Racha-Lechkhumi and Kvemo Svaneti region, Tsageri Municipality, the slope of the Rioni river in the vicinity of Tvishi village , Verdzistava I Cave , 42°31’34.6”N 42°47’34.0”E, 437 m a.s.l., in the subterranean syphon, 10 v.2020, coll. E. Maghradze & Sh. Barjadze.

Paratypes: 1♀ (bl. 12 mm), IZISU,—same locality and date as for holotype .

Additional material: 2♀♀ (partially broken, mostly used for SEM and DNA analysis), LEMMI,—same locality and date as for holotype .

Etymology. The species is named after the Tvishi village Tsageri Municipality, Racha-Lechkhumi and Kvemo Svaneti region, Georgia, near which the Verdzistava I Cave is located, where a new species was discovered.

Diagnosis. Urosomite II with 4 slender dorsoposterior spine-like setae on each side. Epimeral plates I-III subangular, with rounded 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 7 – 10 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 2.5 times shorter than 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 e ).

Epimeral plates I–III subangular, with rounded posteroventral corner, ventral margin of epimeral plates II and III armed with 4 small simple spines ( Fig. 9 a–c ).

Urosomite I armed with 2 slender dorsoposterior setae on each side; urosomite II with 4 slender dorsoposterior spine-like setae on each side; urosomite III unarmed ( Fig. 10 c ).

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

Antenna I ( Fig. 6 a ) slender, long; peduncular articles moderately slender, ratio 1:0.90:0.47; flagellum consisting of about 21 articles, most of them with 2 short aesthetascs each; accessory flagellum short, 2-articulated.

Antenna II ( Fig. 6 b, c ) with peduncular article 3 almost equal to article 2, about 4.5 times as long as wide, with separate rare tufts of long setae along distoventral margin; article 2 about 3.5 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. 7 a ) entire, with convex dorsal margin, covered with tiny setae. Labrum ( Fig. 7 b ) entire, slightly broader than long, with entire outer lobes and developed inner lobes exceeding half of outer lobes. Mandibles ( Fig. 7 c–f ) with mandibular palp ( Fig. 7c, e ) consisting of 3 articles: article 1 about 1.5 times as long as wide, smooth; article 2 about 3 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 7–8 A-setae; 2 groups of B-setae; 26 D-setae and 6 Esetae. Maxilla I ( Fig. 7 g ) with: inner plate with relatively short 2 long distal simple setae, outer plate with 7 robust spines armed with 1 small lateral tooth each, the lowest spine with several tiny ventral teeth ( Fig. 7 h ); palp 2-articulated, distal article with a tuft of long simple setae distally. Maxilla II ( Fig. 7 i ) with smooth well-developed lobes armed with numerous distolateral setae, distal margins with long simple setae. Maxilliped ( Fig. 7 j ) with short inner plate armed with 3 distal simple strong spines; outer plate reaching half of palpal 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. 6 d, f ).

Gnathopod I ( Fig. 6 d ) with basis robust, about 2.5 times as long as wide, with long simple setae along posterior and posterodistal margins; ischium almost quadrate, as long as wide, similar to article 4; 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; article 6 (propodus) large, slightly broader than longer, with several 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. 6 e ); dactylus strong and sharp, reaching posterior margin of article 6, with a row of small numerous setae along dorsal margin.

Gnathopod II ( Fig. 6 f ) with basis relatively slender, about 4 times as long as wide, with long simple setae along posterior and postero-distal margins; ischium almost about as long as wide, similar to article 4; 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; article 6 (propodus) large, slightly broader than longer, 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. 6 g ); dactylus strong and sharp, reaching posterior margin of article 6, with a row of small numerus setae along dorsal margin.

Pereopods III–IV ( Fig. 8 a, c ) 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 article 6, 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 ) relatively slender, curved, sharp distally, with small ventral median spine.

Pereopods V–VI ( Fig. 8 e, g ) with basis almost subrectangular, about 2 times as long as wide, slightly widening proximally, without posteroventral lobe, anterior margin of article 2 slightly convex, with a row of slender marginal setae that slightly longer than posterior; ischium small, subquadrate, as long as wide; carpus about 4 times as long as wide, with short setae along dorsal and ventral margins; merus robust, about 4–4.5 times as long as wide, almost equal to article 4; 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. 8 f, h ).

Pereopod VII ( Fig. 8 i ) 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 article 6, 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. 8 j ).

Pleopods normal, without specific features, with 7–10 hooks in retinacules, without additional setae ( Figs 9 g , 11 f ).

Uropod I ( Fig. 9 h, i ) with protopodite (peduncle) about 4 times as long as wide, slightly longer than rami, with a dorso-external 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. 9 j, k ) 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. 9 l, m ) different in males and females. Uropod III in females ( Fig. 9 l ) 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. 9 m ) with protopodite about 1.5 times as long as wide, rami unequal, inner ramus short, about 10 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. 9 d, e ) 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 spines on each side; distal and marginal spines relatively long and slender, reaching about 0.5 of length of telson.

Body size. The largest collected ♀ has bl. 12 mm; the largest ³ has bl. 15 mm.

GenBank accession number. MW014293–MW014296.

Taxonomic remarks. From mostly related N. borutzkyi , the new species can be separated by (1) shorter distal segment of uropod III in females, which is more than 5 times shorter than the previous segment ( Fig. 5 l ) vs. about 4 times as long as wide ( Marin 2020: Fig. 7 e ); (2) shorter distal segment of uropod III in males, which is more than 2 times shorter than the previous segment ( Fig. 9 l ) vs. equal ( Yuzbashyan 1942: Fig. 3 ); and (3) 4 small spines along ventral margins of epimeral plates II–III ( Fig. 9 b, c ) vs. 5 spines ( Birštein 1933: Abb. 7).

From N. amirani , the new species can be clearly separated by (1) 4 stouter and shorter dorsoposterior spine-like setae on urosomite II ( Fig. 10 d ) vs. 3 slender spine-like setae ( Marin 2020: Fig. 8 a ); (2) shorter distal segment of uropod III in females, which is more than 5 times shorter than the previous segment ( Fig. 9 m ) vs. about 3 times as long as wide ( Marin 2020: Fig. 7 e ); and (3) shorter distal segment of uropod III in males, which is more than 2 times shorter than the previous segment ( Fig. 9 l ) vs. equal ( Marin 2020: Fig. 7 f ).

From Niphargus rachalechkhumensis sp. nov., described above, the new species can be easily separated by (1) epimeral plate III with non-produced posteroventral angle, almost rectangular ( Fig. 9 c ) vs. distinctly bluntly produced posteroventral angle ( Fig. 5 c ); (2) urosomite II with 4 slender spine-like setae ( Fig. 10 d ) vs. with 3 stout spine-like setae ( Fig. 10 a ); (3) main (basal) part of dactyli of pereiopod VI–VII not more than 2.5–3 times longer wide ( Fig. 8 ) vs. about 4 times longer wide ( Fig. 4 ); (4) distal segment of uropod III more than 2 times shorter than previous one in males ( Fig. 9 l ) vs. about 1.5 times shorter than previous one ( Fig. 5 m ); and (5) the presence of 7–10 hooks in retinacules of pleopods vs. 6–7 hooks.

Ecology and distribution. Niphargus tvishiensis sp. nov. is presently known from only the type locality, the Verdzistava I Cave. Lekhumian Tvishi Cave mentioned in Djanashvili & Barjadze (2011) and Djanashvili et al. (2014) should be also named as Verdzistava I Cave, from where two springtail species are known: Argonychiurus multiocellatus Djanashvili, Barjadze, Jordana et Burkhardt, 2014 (Onychiuridae) (troglobiont) and Plutomurus birsteini Djanashvili et Barjadze, 2011 (Tomoceridae) (troglophile).

Figures

FIGURE 3. Niphargus rachalechkhumensis sp. nov., holotype, ³, ZMMU Mb-1245, Sakishore Cave: a—labrum (upper lip); b—labium (lower lip); c, e—mandible; d, f—incisor and incisive processes of mandible; g—maxilla I; h—same, distal margin of outer lobe; i—maxilla II; j—maxilliped.

FIGURE 4. Niphargus rachalechkhumensis sp. nov., holotype, ³, ZMMU Mb-1245, Sakishore Cave: a—pereopod III; b— dactylus of PIII; c—pereopod IV; d—dactylus of pereopod V; e—pereopod V; f—dactylus of pereopod V; g—pereopod VI; h—dactylus of pereopod I; i—pereopod VII; j—dactylus of pereopod II.

FIGURE 5. Niphargus rachalechkhumensis sp. nov., Sakishore Cave, holotype, ³, ZMMU Mb-1245 (a–d, h, j–l) and paratype, ♀, ZMMU Mb-1246 (e, i): a–c—epimeral plates I–III; d, e—telson; f—pleopod I; g—retinacula of pleopod I; h, i—uropod I; j, k—uropod II; l, m—uropod III.

FIGURE 6. Niphargus tvishensis sp. nov., holotype, ³, ZMMU Mb-1247, Verdzistava I Cave: a—antenna I; b—accessory flagellum of antenna I; c—antenna II; d—gnathopod I; e—distoventral corner of propodus (chela) of gnathopod I; f—gnathopod II; g—distoventral corner of propodus (chela) of gnathopod II.

FIGURE 7. Niphargus tvishiensis sp. nov., holotype, ³, ZMMU Mb-1247, Verdzistava I Cave: a—labrum (upper lip); b—labium (lower lip); c, e—mandible; d, f—incisor incisive processes of mandible; g—maxilla I; h—same, distal margin of outer lobe; i—maxilla II; j—maxilliped.

FIGURE 8. Niphargus tvishiensis sp. nov., holotype, ³, ZMMU Mb-1247, Verdzistava I Cave: a—pereopod III; b—dactylus of PIII; c—pereopod IV; d—dactylus of PIV; e—pereopod V; f—dactylus of PV; g—pereopod VI; h—dactylus of PVI; i—pereopod VII; j—dactylus of PVII.

FIGURE 9. Niphargus tvishiensis sp. nov., Verdzistava I Cave, holotype, ³, ZMMU Mb-1247 (a–d, h, j–l) and ♀, LEMMI (e, i): a–c—epimeral plates I–III; d, e—telson; f—pleopod I; g—retinacula of pleopod I; h, i—uropod I; j, k—uropod II; l, m—uropod III.

FIGURE 10. Niphargus rachalechkhumensis sp. nov. (a, b) and Niphargus tvishiensis sp. nov. (c–f), non-type specimens, ♀♀, LEMMI: a, c, d—urosomal segments, lateral view; b, e—head; f—mandibular palp.

FIGURE 11. Retinacules of pleopods of Niphargus borutzkyi Birštein, 1933 (a, b), Niphargus amirani Marin, 2020 (c, d), Niphargus rachalechkhumensis sp. nov. (e) and Niphargus tvishiensis sp. nov. (f), non-type specimens, ♀♀, LEMMI.