Niphargus bzhidik, Marin & Krylenko & Palatov, 2021

Marin, Ivan, Krylenko, Sergey & Palatov, Dmitry, 2021, The Caucasian relicts: a new species of the genus Niphargus (Crustacea: Amphipoda: Niphargidae) from the Gelendzhik-Tuapse area of the Russian southwestern Caucasus, Zootaxa 4963 (3), pp. 483-504 : 486-496

Niphargus bzhidik sp. nov.

( Figs 1–9 )

http://www.zoobank.org/ urn:lsid:zoobank.org:act:E0019189-2432-4B64-B153-94C43FDD93E3

Material examined. Holotype.— RUSSIA, 1♂ (bl. 8.5 mm), ZMMU Mb-1160, Southwestern Caucasus, Krasnodar region, Gelendzhik area, st. P1, in a small spring in a tributary of Pshada River , 44°28’08.71”N 38°25’54.64”E, hand net, S. Krylenko leg., 06 Jan. 2019.

Paratypes. RUSSIA, 2♀♀ (bl. 7.0 and 6.0 mm), ZMMU Mb-1161, 1162, same data and locality as holotype .

Additional material. RUSSIA, 5♀♀, LEMMI, Gelendzik area , st. C1, a small puddle in the Skupkova Schel, 44°28’17.09”N 38°26’00.05”E, hand net, S. Krylenko leg., 06 Jan. 2019 ; 1♂, 1♀, LEMMI, Gelendzik area , st. Т2 , a small spring in the Tekos riverbed near Arhipo-Osipovka village, 44°24’02.92”N 38°30’45.57”E, hand net, S. Krylenko leg., 06 Jan. 2019 ; 7♀♀, LEMMI, Gelendzik area , st. B3, Tekos river valley, a small spring in the Butylochnaya Schel, 44°27’32.21”N 38°26’58.76”E, hand net, coll. S. Krylenko, 06 Jan. 2019 ; 1♂, 2♀♀, LEM- MI, Gelendzik area , st. G2, a small spring in the Teshebs riverbed, 44°22’29.68”N 38°37’49.09”E, hand net, S. Krylenko leg., 06 Jan. 2019 ; 5♀♀, LEMMI, Tuapse area , st. B2, a small spring in the Bzhid riverbed, 44°22’05.64”N 38°38’35.55”E, hand net, S. Krylenko leg., 06 Jan. 2019 ; 1♂, 4♀♀, LEMMI, Tuapse area , st. B1, a puddle in the Bzhid riverbed, 44°22’01.28”N 38°38’36.36”E, hand net, S. Krylenko leg., 06 Jan. 2019 .

Etymology. The species is named after the Bzhid River, in the valley of which it was discovered for the first time; the ending (- ik) is added as the designation “ living here ”, very common and characteristic features of the Russian language in this region.

Diagnosis. Head without pigmented spots on anterior lobe. Posteroventral corners of epimeral plates I–II rounded, sharp in epimeral plate III. Urosomite II with 1 spine one on each side. Dactyli of pereopods III–VII with a small ventral inner spine. Rami of uropod I unequal in size: outer ramus about 1.5 times larger than inner one in males and slightly larger than inner one in females. Pleopods with 2 hooks in retinacules. Telson with 3–4 relatively long distal spines, medium lateral spines, accompanying by 2 plumose setae on each side; dorsal surface with 1 large dorsal submarginal spine on each side, accompanying by 2 plumose setae, and 2–5 simple short dorsal spines in proximal part of telson.

Description. BODY: moderately slender; maximum body length in males is 8.5–9.0 mm, females slightly smaller, about 6.0–8.0 mm. HEAD ( Fig. 7 a, b ): large, without rostrum and pigmented spots on anterior lobe, with subrounded lateral cephalic lobes and excavated anteroventral sinus.

MESOSOMA: mesosomal segments smooth.

METASOMA: metasomal segments I–III with several short marginal setae on each posterodorsal margin.

EPIMERAL PLATES ( Fig. 6 a–c ): epimeral plates I–II with rounded posteroventral corners ( Fig. 6 a, b ), epimeral plate 3 with sharp posteroventral corner ( Fig. 6 c ). Epimeral plate I without ventrofacial setae, but with convex posterior margin bearing 5–6 short marginal setae, and subrounded posteroventral corner marked with 1 strong seta. Epimeral plate II with 3 ventrofacial setae, with convex posterior margin bearing 7 short marginal setae, and subrounded posteroventral corner marked with 1 strong seta. Epimeral plate III concave posterior margin bearing 7 short setae, and with marked posteroventral corner with 1 strong corner seta; 4 subventral spines on epimeral plate III.

UROSOMITES ( Fig. 7 c, e ): Urosomite I with 1 seta on each dorsolateral side, with 1–3 posteroventral spines near basis of uropod I; urosomite II with 1 simple strong spine and 1 seta on each dorsolateral side; urosomite III unarmed.

COXAE: coxae I–IV moderately large, with short ventromarginal setae: coxa I nearly as long as broad, with subrounded anteroventral corner; coxa II nearly as long as broad, with rounded anteroventral corner; coxae III–IV as short as broad; coxae V–VII shorter than coxa IV; coxa V with 6 setae on anterior, and 5 setae at posterior lobe; coxa VI with 2 setae on anterior, and 3 setae at posterior lobe; coxa VII with 1 seta at posterior lobe.

COXAL GILLS: occur on legs 2–6, ovoid, relatively large; ratio of length of gills/bases pereopod are 0.8/1; 0.86/1; 1.05/1; 1.2/1 and 0.8/1, respectively. Oostegites occur on pereopods 2–5.

ANTENNA I ( Fig. 3 a ): slender; peduncular articles moderately slender, ratio: 1/0.8/0.45; main flagellum consisting of about 20 articles, most of them with 2 short aesthetascs each; accessory flagellum short, 2-articulated ( Fig. 3 b ).

ANTENNA II ( Fig. 3 c ): stout, peduncular article 3 short, slightly broadened than wide; peduncular article 5 shorter than article 4, with several long setae along ventral margin, dorsal setae shorter than inner ones; flagellum is about 0.8 of peduncular articles 4+5, relatively short, consisting of about 9–10 articles with relatively short setae. Antennal gland cone blunt, not exceeding peduncular article 3.

LABRUM (upper lip) ( Fig. 4 a ) typical, entire, subrounded.

LABIUM (lower lip) ( Fig. 4 b ): entire, broader than long, with entire outer lobes and developed inner lobes, not exceeding the 1/3 of the length of outer lobes.

MANDIBLES ( Fig. 4 c, f ): incisor process and pars incisiva similar to other Niphargus species ( Fig. 4 d, e ). Incisor of left mandible with 5 teeth, lacinia mobilis with 4 teeth and row of 8 arcuate setae with lateral projections; incisor of right mandible with 4 teeth, lacinia mobilis bifurcate, pluritoothed and row of 8 arcuate setae with lateral projections; Mandibular palp article ratio is 1:2:2 and represent 29%, 39% and 32% of total length of palp, respectively. Mandibular palp 3-articulate: article 1 smooth with pronounced neck; article 2 with 7–10 setae, palp article 3 subfalciform, barely longer than article 2, with 20 marginal D-setae and 5 long distal E-setae; on the outer face appears one group of 5 A-setae, on the inner face with 3 groups of B-setae, without C-setae ( Fig. 7 f ).

MAXILLA I ( Fig. 4 g ): inner plate with 3 distal setae, outer plate with 7 robust spines (6 spines with 1 strong lateral tooth each, inner spine with 3 small lateral teeth (1–1–1–1–1–1–3)) ( Fig. 4 h ); palp 2-articulated, distal article with 6–7 simple setae distally.

MAXILLA II ( Fig. 4 i ): with smooth well developed plate armed with distolateral setae only.

MAXILLIPED ( Fig. 4 j ): inner plate short, with four distal spines intermixed with 5 distal simple setae, outer plate reaching half of palpus article 2 and bearing a row of 18–19 distolateral spines and distal setae; palpus article 3 with 1 median and 1 distal bunch of setae at outer margin; palpus article 4 with 1 median seta at outer margin; nail shorter than pedestal, with seta near basis.

GNATHOPOD I ( Fig. 3 d ): with article 2 robust, expanded distally, about twice longer than wide, with long simple setae along posterior and posterodistal margins; article 3 almost quadrate, as long as wide, similar to article 4, with posterior apical group of setae; article 4 quadrate, about as long as wide, with a row of setae along posterior margin; article 5 trapezoid in shape; article 6 (propodus) large, nearly as long as broad, trapezoid, with 4 groups of posterior marginal setae, with poorly convex and slightly serrated palmar margin, covered with medium simple setae; defined on outer face ( Fig. 3 d, e ) by corner S-spine accompanied laterally by 2 serrate Lspines and 4 facial corner long M-setae, on inner face by one short subcorner R-spine; dactylus strong and sharp, reaching the posterior margin of article 6, with a row of small numerous simple setae along dorsal margin.

GNATHOPOD II ( Fig. 3 f ): slightly larger than gnathopod I; article 2 about 3 times as long as wide, with long simple setae along posterior and posterodistal margins; article 3 quadrate, with 1 median group of setae along posterior margin; article 4 rectangular, about 1.5 times as long as wide, with a row of setae along posteromedian margin; article 5 subtrapezoid in shape, significantly shorter than article 6; article 6 (propodus) large, subtrapezoid, nearly as long as broad, with 5–6 groups of posterior marginal setae; palmar margin poorly convex, oblique almost 2/3 of propodus length, with medium simple setae; provided on outer face ( Fig. 3 f, g, h ) by one corner strong robust S-spine accompanied laterally by 2–3 smaller serrate L-spines and 4 corner long M-setae, on inner face by one short subcorner R-spine; dactylus strong and sharp, reaching the posterior margin of article 6, with a row of small numerous simple setae along dorsal margin.

PEREOPODS III–IV ( Fig. 5 a, c ): almost similar in size and shape, with robust articles; article 2 about 3.5 times as long as wide, with posterior margin bearing long marginal setae; articles 3 short, about as long as wide; article 4 about 3.5 times as long as wide, with slender simple setae along dorsal and ventral margins; articles 5 significantly almost equal to article 6, about 2.5 times as long as wide; article 6 about 4–4.5 times as long as wide, with bunches of spines along ventral margin; dactylus ( Fig. 5 b, d ) robust, relatively stout, curved, sharp distally, with 1 small ventral inner spine and 1 median short plumose seta at outer margin, with nail slightly shorter than pedestal.

PEREOPOD V ( Fig. 5 e ): with article 2 almost rectangular, with feebly marked posteroventral lobe, posterior margin barely concave in the middle with a row of 12 slender marginal setae, without facial setae, anterior margin of article 2 convex, with a row of 4 slender marginal setae that distinctly longer than posterior and bunch of setae in the distal part of article 2; article 3 subquadrate, as long as wide; article 4 about twice as long as wide, with bunches of slender spines along dorsal and ventral margins; article 5 slender, about 3.5 times as long as wide, equal to article 6; article 6 slender, about 4–5 times as long as wide, with bunches of short spines; dactylus ( Fig. 5 f ) short, with 1 small ventral inner spine and 1 median short plumose seta at outer margin.

PEREOPOD VI ( Fig. 5 g ): moderately slender, article 2 wide, about as long as broad, with a distinct posteroventral lobe and convex posterior margin with a row of 14 short marginal setae; anterior margin convex, with a row of 5 longer marginal setae; article 3 short, as long as wide; article 4 about 2.5 times as long as wide, with bunches of short spines along dorsal and ventral margins; article 5 slender, about 4.5 times as long as wide, slightly shorter than article 6, with bunches of spines intermixed with single short setae; article 6 slender, about 6–7 times as long as wide, with several bunches of short spines; dactylus ( Fig. 4 h ) slender, with 1 small ventral inner spine and 1 short median plumose seta at outer margin, with nail much shorter than pedestal.

PEREOPOD VII ( Fig. 5 i ): moderately slender, article 2 narrow, nearly twice as long as broad, with distinct posteroventral lobe, and with a convex posterior margin bearing a row of 10–11 short marginal setae; anterior margin convex, with a row of 6 longer marginal setae; article 3 short, as long as wide; article 4 about 2.5 times as long as wide, with bunches of short spines along dorsal and ventral margins; article 5 slender, about 4.5 times as long as wide, slightly shorter than article 6, with bunches of spines intermixed with single short setae; article 6 slender, about 6–7 times as long as wide, with several bunches of short spines; dactylus ( Fig. 4 j ) slender, with 1 median spine and 1 seta at inner margin, and 1 short median plumose seta at outer margin, with nail much shorter than pedestal.

PLEOPODS ( Fig. 6 f ): basal segment (peduncle) of pleopods I covered with numerous plumose setae, with 2 hooks in retinacule only; basal segment of pleopod II, with 2 hooks and 1 large simple seta in retinacule ( Fig. 6 g ); basal segment of pleopod III with 6 short setae and 2 hooks in retinacule.

UROPOD I ( Fig. 6 h, i ): protopodite (peduncle) much more longer than wide, about twice longer that inner ramus and almost equal to outer ramus, with dorsoexternal row of 3 spines + 1 basal spiniform setae, and dorsointernal row of 3 spiniform setae; rami unequal in length both in males ( Fig. 6 h ) and females ( Fig. 6 i ); outer ramus more than 1/3 times larger than inner one, not paddle-like, inner ramus with lateral and distal relatively robust spiniform setae.

UROPOD II ( Fig. 6 j ): protopodite (peduncle) nearly 2 times longer than wide, about as long as inner ramus and slightly shorter than outer ramus (without distal spines), outer ramus barely longer than inner one, both rami with lateral and distal slender spines.

UROPOD III ( Fig. 6 k–m ): different in males and females, with protopodite about 2–2.2 times as long as wide, rami unequal, inner ramus (endopod) short, nearly 8.5 times shorter than outer (exopod) ramus in females ( Fig. 6 k, l ) and nearly 7.3 times in males ( Fig. 6 m ), bearing several small distal and lateral spines; outer ramus long, proximal article about 8 times as long as wide in females ( Fig. 6 k, l ) and 9.5 times in males ( Fig. 6 m ); distal article is 0.8–0.9 of length of proximal article, with 2 groups of short thin-flexible setae along each margin and group of simple setae apically in males ( Fig. 6 m ) and about 0.4–0.42 of length of proximal article, with 1–2 groups of long flexible setae along each margin and group of simple setae apically in females ( Fig. 6 k, l ).

TELSON ( Fig. 6 d, e ): stout, subquadrate, variable in shape, from about as long as broad ( Fig. 6 e ) to remarkably broader than wide ( Fig. 6 d ), ca 75% incised, lobes obtuse and sloping distally. The armature of the telson is variable, bearing 3 slender distal spines, reaching 0.4–0.25 of the length of telson, with several separate smaller lateral spines; dorsal surface of telson with 1 large dorsal submarginal spine on each side, accompanying by 2 plumose setae, with 2–5 simple short dorsal spines in proximal part of telson.

Coloration. Body coloration of alive animals varies from completely white to pinky or light orange.

Body size. The largest collected female has bl. 8.0 mm; the largest collected male has bl. 9.0 mm.

Genbank numbers. MW771538 – MW771545 .

Habitat and ecology. The new species belongs to the “ puteanus ” group, which include mainly epigean species. The new species was found in various seeping groundwater sources in the several river valleys (see below), i.e. springs and wells, and in river beds under fallen leaves or under stones in the areas with a weak current. Most of the specimens were collected in small weak-current springs (sometimes seasonal), with the depth about 5 cm, and muddy/silty bottom, filled with beech ( Fagus sp. ) and hornbeam ( Carpinus sp. ) leaves. In such habitats crustaceans usually hid under the fallen leaves or stones. Some specimens were collected in small puddles (about 10 cm deep and existing only during a period of strong moisture) with an earthen bottom, covered with many fallen leaves.

Distribution. Niphargus bzhidik sp. nov. shows a local distribution and is found in the drainage valleys (basins) of several neighboring small mountain rivers, namely Pshada (Skupkova Schel only), Vulan (with a tributary of Tekos River), Teshebs and Bzhid, flowing into the Black Sea in the Tuapse area of the Krasnodar region, Russia (see Fig. 1 ). For example, the length of Bzhid River (the type locality) is about 13 kilometers, with the drainage basin about 77 km 2. No specimens of the new species were found in other similar neighboring rivers of the region.

Taxonomic remarks. Niphargus bzhidik sp. nov. belongs to the “ puteanus ” species group (selected and discussed by Karaman (2016)), revealing such morphological similarities with other species of the group known in the Western Europe, Romania, Turkey and the Caucasus as the presence of 2 hooks in retinacules on pleopods, specific uropod I with different rami in males and females, and the comparatively large inner ramus of uropod III (see above; Marin & Palatov, 2019). The new species is mostly morphologically similar to the southwestern Caucasian Niphargus ciscaucasicus and the eastern Georgian N. talikadzei , which have similar different rami of uropod I and III ( Lagidze et al. 1974; Marin & Palatov 2019a).

At the same time, the new species can be clearly separated from N. ciscaucasicus ( Marin & Palatov, 2019a) by 1) the absence of yellow spots on anterior area of the head; 2) slightly produced and blunt posteroventral angles of epimeral plates II and III; 3) shorter and thicker segments of antenna I; 4) the presence of 2 teeth on spines of outer lobe of maxilla 1 (vs. numerous in N. ciscaucasicus ); 5) the presence of only 2 serrated spines on outer face of palm of gnathopods I–II (4 spines in N. ciscaucasicus ); 6) shorter, not paddle-like, outer ramus of uropod I; 7) shorter inner ramus of uropod III both in males and females; and 8) less armored telson.

The other Caucasian species of the group, N. talikadzei , described as soil-dwelling species from the marshlands of Adjara ( Lagidze et al. 1974), clearly differs from the new species by 1) not produced and blunt posteroventral angle of epimeral plates II and, especially of epimeral plate III; 2) the presence of 3 serrated spines on the outer face of palms (chela) of gnathopods I–II; 3) relatively longer paddle-like outer ramus (exopodite) of uropod I; 4) relatively shorter inner ramus of uropod III both in males and females; and 5) less armored telson, especially shorter distal spines.

From epigean Niphargus magnus Birštein, 1940 , which also has 2 hooks in retinacules on pleopods and different rami of uropod I, the new species can be clearly separated by the absence of specific spoon-shaped process on uropod I, significantly larger inner ramus of uropod III and the presence of only 1 ventral inner spine of dactyli of ambulatory pereopods. Moreover, males of the new species are well distinguished from the Caucasian congeners by the large endopod of uropod III, which is at least 1/3 of the length of the first segment of exopodite.

From the other morphologically similar species, namely Niphargus abchasicus Martynov, 1932 , N. iniochus Birštein, 1941 , N. eugeniae Derzhavin, 1945 , N. otharicus Birštein 1952 and N. derzhavini Birštein 1952 , reported in the Caucasus by Martynov (1932) and Birštein (1952), the new species can be easily distinguished by the absence of a characteristic spoon-shaped process on uropod I, different rami of uropod I and the presence of only 1 ventral inner spine of dactyli of ambulatory pereopods and produced shape of the posteroventral angle of epimeral plates I–III.

The key for the separation of the Caucasian and the Eastern Asian species of the genus Niphargus , known from the territory of the former USSR is presented below.

Figures

FIGURE 1. The map of distribution of Niphargus bzhidik sp. nov. (tringles) and relative Niphargus ciscaucasicus Marin & Palatov, 2019 (red star) in the southwestern Caucasus.

FIGURE 2. Reconstruction of phylogenetic relations of Niphargus bzhidik sp. nov. within the genus Niphargus based on COI mtDNA gene marker (ML algorithm, GTR+G+I model).

FIGURE 3. Niphargus bzhidik sp. nov., male: a—antenna I; b—accessory flagellum of antenna I; c—antenna II; d—gnathopod I; e—palmar margin of chela of GnI; f—gnathopod I; g, h—palmar margin of chela of GnII of different specimens.

FIGURE 4. Niphargus bzhidik sp. nov., male: a—upper lip; b—lower lip; c, f—mandibles; d, e—incisor process and pars incisiva; g—maxilla I; h—distal margin of upper endite; i—maxilla II; j—maxilliped.

FIGURE 5. Niphargus bzhidik sp. nov., male: 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 6. Niphargus bzhidik sp. nov., male: (a–c, e–h) and female (d, i–l): a–c—epimeral plates I–III; d, e—telson; f—pleopod III; g—retinacule of pleopod II; h, i—uropod I; j—uropod II; k, l, m—uropod III.

FIGURE 7. Niphargus bzhidik sp. nov., male: a—mandibular palp; b—accessory flagellum of antenna 1; c—telson; d—maxilliped; e—distoventral palmar margin of GnI; f—dactylus of PIII; g—dactylus of PVII; h—retinacule of pleopod II.

FIGURE 8. SEM photographs of Niphargus bzhidik sp. nov., male (a–e) and Niphargus ciscaucasicus Marin & Palatov, 2019, male (f): a, b—head; c–f—urosomal segments;

FIGURE 9. Bivariate plot of δ13C and δ15N values (±S.D.) of organic matter and macrozoobenthos from springs and rivers flowing into the Black Sea in the study area (data in the Table 2).