Niphargus primoricus, Marin & Palatov, 2025

Niphargus primoricus sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8

Material examined.

• Holotype, ♂ (bl. 8.0 mm) ( ZMMU Mb-1299 ) – Russian Federation, Krasnodar Kray, Sochi urban district, Khostinskiy district, hyporhean zone of the Khosta River within the boundaries of the Khosta village , 43°30'55.3"N, 39°52'10.1"E, coll. I. Marin & D. Palatov, 23.10.2024 GoogleMaps . • Paratypes, ♂ (bl. 8.0 mm), ♀ (bl. 7.0 mm) ( ZMMU Mb–1300 ) – Russian Federation, Krasnodar Kray, Sochi urban district, Khostinskiy district, hyporhean zone of the mouth of the Khosta River within the boundaries of the Khosta village , 43°30'33.9"N, 39°52'07.0"E, coll. I. Marin & D. Palatov, 23.10.2024 GoogleMaps .

Additional material.

• 3 ♂♂, 7 ♀♀ ( LEMMI) – same data and locality as holotype GoogleMaps ; • 3 ♂♂, 2 ♀♀ – Russian Federation, Krasnodar Kray, Gelendzhik urban district, Golubaya Bukhta (Blue Bay), 44°34'35.9"N, 37°58'48.3"E, pebble beach near the mouth of Ashamba River , in coastal pebble, coll. I. Marin, 12.07.2023 GoogleMaps ; • 2 ♂♂, 3 ♀♀ (bl. 7.0 mm) ( LEMMI) – Russian Federation, Krasnodar Kray, Gelendzhik urban okrug, hyporhean zone of the mouth of the Betta River within the boundaries of the Betta village , 44°22'16.67"N, 38°23'48.84"E, coll. I. Marin & D. Palatov, 12.06.2024 GoogleMaps ; • 3 ♀♀ – Russian Federation, Krasnodar Kray, Tuapse district, hyporheic zone of the mouth of the Agoy River within the boundaries of the Agoy village , 44°08'06.75"N, 39°01'33.5"E, coll. I. Marin & D. Palatov, 07.06.2024 GoogleMaps ; • 1 ♂, 6 ♀♀ – Russian Federation, Krasnodar Kray, Tuapse district, hyporhean zone of the mouth of the Nebug River within the boundaries of the Nebug settlement , 44°09'41.6"N, 38°59'52.4"E, coll. I. Marin & D. Palatov, 07.06.2024 GoogleMaps ; • 4 ♀♀ – Russian Federation, Krasnodar Kray, Tuapse district, Nechepsukho River in the Novomikhaylovsky village, under the pedestrian bridge , 44°14'52.24"N, 38°50'35.37"E, coll. I. Marin & D. Palatov, 08.06.2024 GoogleMaps ; • 2 ♂♂, 3 ♀♀ – Russian Federation, Krasnodar Kray, Tuapse district, hyporhean zone of the Agoy River within the boundaries of the village of Agoy , 43°57'45.8"N, 39°16'04.3"E, coll. D. Palatov, 14.07.2020 GoogleMaps ; • 1 ♂, 6 ♀♀ – Russian Federation, Krasnodar Kray, Tuapse district, pebble beaches in the valley of the Tu River near its mouth in the Olginka village , 44°11'28.12"N, 38°53'05.52"E, coll. I. Marin & D. Palatov, 08.06.2024 GoogleMaps ; • 2 ♀♀ ( LEMMI) – Russian Federation, Krasnodar Kray, Tuapse district, hyporhean zone of the mouth of the Dederkoy River upstream from the Dederkoy village , 44°04'00.4"N, 39°08'22.8"E, coll. I. Marin & D. Palatov, 13.05.2019 GoogleMaps ; • 4 ♀♀ – Russian Federation, Krasnodar Kray, Sochi urban district, Lazarevsky district, Makopse River under the railway bridge, near the river mouth , 43°59'34.11"N, 39°12'37.98"E, coll. I. Marin & D. Palatov, 06.06.2024 GoogleMaps ; • 1 ♀ – Russian Federation, Krasnodar Kray, Sochi urban district, Lazarevsky district, Kuapse River near the Nizhnyaya Mamedka village , 43°57'10.72"N, 39°18'43.1"E, coll. I. Marin & D. Palatov, 05.06.2024 GoogleMaps ; • 2 ♀♀ – Russian Federation, Krasnodar Kray, Sochi urban district, Lazarevsky district, Ashe River mouth , 43°57'28.8"N, 39°15'41.1"E, coll. I. Marin & D. Palatov, 05.06.2024 GoogleMaps ; • 3 ♂♂, 12 ♀♀ – Russian Federation, Krasnodar Kray, Sochi urban district, Khostinskiy district, hyporhean zone of the mouth of the Khosta River within the boundaries of the Khosta village , 43°30'33.9"N, 39°52'07.0"E, coll. I. Marin & D. Palatov, 15.05.2019 GoogleMaps ; • 3 ♀♀ – Russian Federation, Krasnodar Kray, Sochi urban district, Lazarevsky district, Psezuapse River near the Lazarevskoye village, 200 m upstream from the mouth , 43°53'57.35"N, 39°20'03.97"E, coll. I. Marin & D. Palatov, 03.06.2024 GoogleMaps .

Diagnosis.

Head with small yellow pigmented spots on anterior lobe. Posteroventral corners of epimeral plates I – III bluntly rounded. Urosomite I unarmed; urosomite II with one simple seta on each side dorsolaterally; urosomite II with two strong spines on each side dorsolaterally. Propodus of gnathopods I and II subtrapezoidal, with its width shorter than depth; dactylus with numerous simple setae along outer margin. Dactyli of pereopods III – VII with one small additional median spine and one median short plumose seta at outer margin. Rami of uropod I unequal in size: endopodite ~ 1.8 × longer than exopodite in mature males, and 1.2–1.25 × longer than exopodite in small males and females, with tufts of well-seen long curved setae in both sexes; exopodite of uropod III differ in males and females, significantly longer in males. Pleopods with two hooks in retinacles. Telson with two, three, or four medium-sized distal spines on each lobe and one or two lateral spines, accompanied by two small plumose setae, and its dorsal surface with none or one small or medium submarginal spine on each side and none or one small mesial seta.

Description

(based on holotype male, ZMMU Mb-1299 ). Body depigmented, stygomorphic, moderately slender (see Fig. 2 View Figure 2 ).

Head (Fig. 2 B View Figure 2 ): length is ~ 7.5 % of body length; rostrum and pigmented spots on anterior lobe absent, with bluntly produced anteroventral lobes and excavated anteroventral sinus. Eyes cornea absent, but small pigmented yellow spots well seen on head (Fig. 2 B View Figure 2 ).

Pereon: pereonites I – VII without setae, smooth.

Pleosoma: pleonites I – III with several short marginal setae on each posterodorsal margin.

Epimeral plates (Fig. 7 A, C, E View Figure 7 ). Posteroventral corners of epimeral plates I and II rounded (Fig. 7 A, C View Figure 7 ), epimeral plate III with posteroventral corner posteriorly produced, nearly right-angled (Fig. 7 E View Figure 7 ). Epimeral plate I (Fig. 7 A View Figure 7 ): posterior margin convex, ventral margin slightly convex; without spines along ventral margin; with eight setae along posterior margin; posteroventral angle with one strong seta. Epimeral plate II (Fig. 7 C View Figure 7 ): posterior and ventral margin convex; with two spiniform setae along ventral margin; eight setae along posterior margin, one of which strong and close to posteroventral angle; posteroventral angle with one strong seta. Epimeral plate III (Fig. 7 E View Figure 7 ): posterior margin almost straight slightly convex, ventral margin slightly convex; with three spiniform setae along ventral margin; with eight setae along posterior margin; posteroventral angle with one strong seta.

Urosomites (Fig. 8 B, D View Figure 8 ): urosomite I with one long simple seta on each side dorsolaterally, with one posteroventral long spine-like near basis of uropod I; urosomite II with two simple strong spines each side dorsolaterally; urosomite III unarmed.

Coxae: coxal plate I (Fig. 5 D View Figure 5 ) oval in shape, with rounded anteroventral margin, armed with 11 setae, width / depth ratio 1 / 1.3; coxal plate II (Fig. 5 G View Figure 5 ) close to quadrate, with rounded anteroventral margin, armed with 8 setae, width / depth ratio ~ 1 / 1.1; width / depth ratio of coxal plates III and IV (Fig. 5 A, C View Figure 5 ) 1 / 0.9 and 1 / 1, respectively; anterior and ventral margins of coxal plates III – IV with ten and seven setae each, respectively; with rounded anteroventral corners; coxal plates V and VI (Fig. 5 E, G View Figure 5 ) with large lobes anteriorly, provided with six and four setae, respectively; posterior margins with three and one setae each, respectively; coxal plate VII (Fig. 5 I View Figure 5 ) semicircular and with one strong and one simple setae on posterior lobe; coxal gills II – VI ovoid of which II and IV more elongated, length ratio of gills / bases of pereopods ~ 0.72 / 1, 0.84 / 1, 0.97 / 1, 0.83 / 1 and 0.73 / 1, respectively.

Antenna I (Fig. 3 A View Figure 3 ): slender, ~ 48–50 % of body length; peduncular articles moderately slender, ratio 1 / 0.8 / 0.31; flagellum with 28 articles, most of them with two short aesthetascs each; accessory flagellum short, bi-articulated (Fig. 3 B View Figure 3 ), with several long apical setae; length ratio of antennas I / II in range of 1 / 0.60–0.75.

Antenna II (Fig. 3 C View Figure 3 ): peduncular articles moderately stout, with several long setae along ventral margin, dorsal setae shorter than inner ones; flagellum relatively short with relatively short setae, consisting in males with 11 articles; peduncular articles II and III short, approx. as long as wide, peduncular articles IV and V slender, ~ 5 × and 6 × longer than wide, respectively, length ratio of 0.98–1 / 0.90 – 0.95; flagellum ~ 0.45–0.48 of length of peduncular articles IV + V.

Labrum (upper lip) (Fig. 4 A View Figure 4 ) typical.

Labium (lower lip) (Fig. 4 B View Figure 4 ): with entire, oblong oval outer lobes and well-developed smaller inner lobes.

Mandible (Fig. 4 C, E View Figure 4 ): Left mandible (Fig. 4 C View Figure 4 ): incisor process with five teeth, lacinia mobilis with four teeth; with row of nine serrated setae between lacinia and molar process (Fig. 4 D View Figure 4 ); mandibular palp proximal article without setae, ~ 2 × longer than wide; mandibular article II / III (distal) ratio 1 / 0.3; article II with 12–13 simple setae; distal article with group of five A-setae; four groups of B-setae; 22 D-setae and six E-setae. Right mandible (Fig. 4 E View Figure 4 ): incisor process with four blunt teeth, lacinia mobilis bifurcate distally, with row of nine serrated setae between lacinia and molar process (Fig. 4 F View Figure 4 ).

Maxilla I (Fig. 3 G View Figure 3 ): inner lobe with three simple distal setae, outer lobe with seven robust spines (2 spines with 2 strong lateral teeth and 3 spines with 1 strong lateral tooth (1–0 – 1 – 0 – 1 – 2 – 2) (Fig. 3 H View Figure 3 )); palp bi-articulated, distal article with four simple setae distally.

Maxilla II (Fig. 4 I View Figure 4 ): both plates with numerous long distal simple setae, outer lobe with row of fine setae along outer margin.

Maxilliped (Fig. 4 J View Figure 4 ): inner plate short, with four distal robust setae intermixed with six distal simple setae; outer plate reaching half of palpal article II and bearing row of 20 or 21 distolateral spines and distal setae; palpal segment III with single median bundle of setae, along with single bundles of setae located at distal edge on both its internal and external surfaces; furthermore, large simple seta is situated at center of external margin of article; palpal article IV with one median seta at outer margin; nail shorter than pedestal, with small seta near basis.

Gnathopod I (Fig. 3 D View Figure 3 ): basis elongated, width / length ratio ~ 0.37 / 1, with distal part greatly expanded, with long simple setae along anterior and posterodistal margins; ischium approx. as long as wide, with group of posterodistal setae; merus subquadrate, equal in size to ischium; carpus approx. as long as wide, ~ 0.40 × of length of basis and 0.46 × of length of propodus, with single distal group of setae anteriorly, with transverse rows of setae along posterior margin and row of setae posterolaterally; propodus subtrapezoidal, ~ 1.25 × longer than wide, setose, with six rows of setae at posterior margin, anterior surface with three groups of total from four to six setae each in addition to anterodistal group of five or six setae; several groups of short setae on inner surface; palmar corner armed with long spiniform palmar seta, two serrated spiniform setae, single supporting spiniform seta on inner surface (Fig. 3 E View Figure 3 ); dactylus with six setae along anterior margin, some of them are grouped in pairs, and with row of short setae along inner surface; length of nail 0.35 × of total length of dactylus.

Gnathopod II (Fig. 3 G View Figure 3 ): basis width / length ratio ~ 0.31 / 1, with distal part greatly expanded, with long simple setae along anteriorly on posterior and posterodistal margins; ischium approx. as long as wide, with three posterodistal setae; merus subquadrate, slightly longer than ischium, with eight posterodistal setae; carpus 0.57 × of length of basis and 0.82 × of length of propodus, with distal group of setae anteriorly, few transverse rows of setae along posterior margin and row of setae posterolaterally; propodus subtrapezoidal, ~ 1.14 × longer than wide, setose, larger than propodus (palm) of GnI (GnI / II as 0.88 / 1), posterior margin with six rows of setae, anterior surface with two groups of setae in addition to six or seven anterodistal setae, with several groups of setae on inner surface, palmar corner with one strong palmar spiniform seta, one supporting spiniform seta on inner surface and two denticulated thick spiniform setae on outer side (Fig. 3 H View Figure 3 ); dactylus with five setae along anterior surface some of them are grouped in pairs and few short setae along inner surface; length of nail ~ 0.34 × of total length of dactylus.

Pereopods III and IV (Fig. 5 A, C View Figure 5 ) almost similar in size and shape; basis ~ 4.1–4.3 × as long as wide, with posterior margin bearing long marginal setae, with distoventral group of setae; ischium short, subquadrate, approx. as long as wide, with distoventral group of setae; merus ~ 4.3–4.4 × longer than wide, with slender simple setae along anterior and posterior surfaces; carpus / propodus ratio ~ 0.95–0.96 / 1; propodus with four groups of spines along ventral margin; dactylus (Fig. 5 B, D View Figure 5 ) relatively stout, curved, sharp distally, with one small additional posterior median spine and one median short plumose seta at outer margin; length of nail ~ 0.4 × of total length of dactylus.

Pereopods V – VII (Fig. 5 E, G, I View Figure 5 ): length ratio of PpV / VI / VII close to 1 / 1.42 / 1.48.

Pereopod V (Fig. 5 E View Figure 5 ): basis almost rectangular, with length / width ratio ~ 1 / 0.61, with explicit posteroventral lobe; with facial setae; posterior margin almost straight with row of 15 slender marginal setae; anterior margin convex, with row of six slender marginal setae, which distinctly longer than posterior ones, and group of setae in distal part; ischium subquadrate, approx. as long as wide, with long posterodistal setae; merus ~ 3.0 × longer than wide, with three slender spines along anterior surface and with two spine on posterior surface; carpus ~ 4.6 × as long as wide, approx. as long as merus, with several bunches of slender spines; propodus slender, ~ 6.0–6.3 × as long as wide, with several bunches of slender spines; dactylus (Fig. 5 F View Figure 5 ) with one small additional posterior median spine and one median short plumose seta at outer margin; length of nail close to 0.27–0.3 × of total length of dactylus.

Pereopod VI (Fig. 5 G View Figure 5 ): basis almost rectangular, with length / width ratio ~ 1 / 0.57, with distinct posteroventral lobe and straight posterior margin bearing row of 16 short marginal setae, anterior margin convex, with row of five longer marginal setae, which distinctly longer than posterior ones, and group of setae in anterodistal part; ischium approx. as long as wide, subquadrate, with long posterodistal setae; merus ~ 3.4 × longer than wide, with several bunches of short spines along anterior and posterior margins; carpus ~ 5.9 × as long as wide, with group of spines intermixed with single short setae; propodus slender, ~ 8.5 × as long as wide, with several group of short spines; dactylus (Fig. 5 H View Figure 5 ) slender, with single small additional posterior median spine and single short median plumose seta at outer margin; length of nail close to 0.3 × of total length of dactylus.

Pereopod VII (Fig. 5 I View Figure 5 ) similar to PVI: basis almost rectangular, with length / width ratio ~ 1 / 0.65, with distinct posteroventral lobe and straight posterior margin bearing row of 13 short marginal setae, anterior margin convex, with row of six longer marginal setae, which distinctly longer than posterior ones, and group of setae in anterodistal part; ischium slightly wider than long, subquadrate, with long posterodistal setae; merus ~ 2.7 × longer than wide, with several bunches of short spines along anterior and posterior margins; carpus ~ 5.1 × as long as wide, with group of spines intermixed with single short setae; propodus slender, ~ 10.0 × as long as wide, with several group of short spines; dactylus (Fig. 5 J View Figure 5 ) slender, with one small additional posterior median spine and one short median plumose seta at outer margin; length of nail close to 0.29 × of total length of dactylus.

Pleopods: pleopod I with basal segments without setae, with two coupling hooks in retinacula and long simple setae above hooks (Fig. 7 J View Figure 7 ); outer and inner rami with 14 and 17 segments, respectively; pleopod II with basal segments without setae, with two coupling hooks in retinacula; outer and inner rami with 13 and 14 segments, respectively; pleopod III with basal segment with two or three long simple setae, with two coupling hooks, with long simple setae above hooks in retinacula; outer and inner rami with 11 and 12 segments, respectively.

Uropod I (Fig. 7 K View Figure 7 ): protopodite ~ 5.5 × longer than wide, with dorso-external row of 10–11 spines or spiniform setae, and dorsointernal row of with four – six thin spines; length ratio of protopodite / endopodite / exopodite ~ 1 / 0.93 / 0.49; endopodite elongated, not paddle-like, with four or five dorsolateral spines accompanied by groups of long bristles and with two long and two short apical spines; exopodite with four dorsolateral spines, accompanied by groups of long bristles and four apical spines.

Uropod II (Fig. 7 M View Figure 7 ): protopodite ~ 3.2 × as long as wide, with dorso-external row of four or five spines or spiniform setae, and dorso-internal row of one or two thin spines; length ratio of protopodite / endopodite / exopodite ~ 1 / 0.99 / 0.75; rami with dorsal, lateral and apical slender spines: endopodite with three dorsal, one dorsolateral and five apical spines; exopodite with four dorsal, three dorsolateral and five apical spines.

Uropod III (Fig. 7 P View Figure 7 ): ~ 0.45 × of body length; protopodite ~ 2.5 × as long as wide, with one small external seta, two small internal setae, and four or five apical spiniform setae; rami unequal, endopodite short, ~ 10–11 × shorter than exopodite, with two small setae laterally and two or three apical setae; proximal article ~ 12 × longer than wide, with seven or eight groups of thin-flexible, plumose and spiniform setae along inner and outer margins; distal article ~ 19 × longer than wide, ~ 0.86 × of length of proximal article, with two simple setae apically.

Telson (Fig. 7 I View Figure 7 ): slightly longer then wide, ~ 1.1 × as long as wide; cleft ~ 0.72–0.8 × of length of telson; margins weakly rounded, narrowing apically; with four or five medium-sized distal spines on each lobe and from one to three lateral spines, accompanied by one or two plumose setae on each side; dorsal surface with one small or medium submarginal spine on each side and with none or one small mesial seta.

Females (Figs 3 F, I View Figure 3 , 6 View Figure 6 , 7 B, D, F – H, L, N, O View Figure 7 ) and small-sized males (Fig. 9 View Figure 9 ). Females are very similar to males in size. Morphologically small-sized males close to females, especially in shape of uropods I – III (see Fig. 9 View Figure 9 ). Gnathopods I and II (Fig. 3 F, I View Figure 3 ) and ambulatory pereiopods (Fig. 6 View Figure 6 ) are almost similar to males. Epimeral plate I (Fig. 7 B View Figure 7 ): posterior margin convex, ventral margin slightly convex; without spines along ventral margin; with seven setae along posterior margin; posteroventral angle with one strong seta; epimeral plate II (Fig. 7 D View Figure 7 ): posterior and ventral margin convex; with two spiniform setae along ventral margin; ten setae along posterior margin, one of which strong and close to the posteroventral angle; posteroventral angle with one strong seta; epimeral plate III (Fig. 7 F View Figure 7 ): posterior margin almost straight slightly convex, ventral margin slightly convex; with three spiniform setae along ventral margin; with eight setae along posterior margin; posteroventral angle with one strong seta. Length of PVII to the total body length ~ 39–40 % in males and 53–55 % in females, respectively (see Fig. 3 View Figure 3 ). Length of the protopodite uropod I is much greater than the width in males than in females, ~ 5.5 × and 5.0 ×, respectively; length ratio of protopodite / endopodite / exopodite ~ 1 / 0.93 / 0.49 in large males (Fig. 7 K View Figure 7 ) and 1 / 0.78 / 0.60 in small males (Fig. 9 D View Figure 9 ) and females (Fig. 7 L View Figure 7 ), respectively. Protopodite of uropod II is shorter in females and small-sized males vs large-sized males, ~ 2.4 × as long as wide in large males (Fig. 7 M View Figure 7 ) and ~ 3.0 × in females (Fig. 7 N View Figure 7 ) and small-sized males (Fig. 9 E View Figure 9 ), respectively; length ratio of protopodite / endopodite / exopodite ~ 1 / 1.06 / 0.84. Uropod III different in large-sized males vs females and small-sized males, ~ 0.43 × of body length in large-sized males (Fig. 7 P View Figure 7 ) and 0.30 × in females (Fig. 7 O View Figure 7 ) and small-sized males (Fig. 9 F View Figure 9 ); distal article ~ 19 × longer than wide in large-sized males (Fig. 7 P View Figure 7 ) and 6.8 × in females (Fig. 7 O View Figure 7 ) and small-sized males (Fig. 9 F View Figure 9 ). Uropod III (Fig. 7 O View Figure 7 ): protopodite ~ 1.9 × as long as wide, with from two to five thin setae laterally and from five to seven spiniform setae apically; rami unequal, endopodite short, ~ 10 × shorter than exopodite, without seta laterally and two or three spiniform setae apically; distal article 0.5 × of length of proximal article, with three or four groups of thin-flexible setae along each margin and group of simple setae apically; proximal article ~ 8.0–9.0 × longer than wide, with four groups of spiniform setae along outer margin and five groups of spiniform setae along inner margin. Telson (Fig. 7 G – I View Figure 7 ) similar both in males and females; cleft ~ 0.65–0.7 × of length of telson.

Coloration.

Body, appendages, and internal organs are whitish or yellowish characteristic to other stygobiotic representatives of the genus Niphargus (see Fig. 2 View Figure 2 ).

Body size.

The largest collected male has bl. 8.0 mm; the largest collected female has bl. 15.5 mm.

GenBank

( NCBI) accession numbers. PX 233131 ( holotype ♂, ZMMU Mb-1299 ), PX 233133 ( paratype ♀, ZMMU Mb-1300 ), PX 233131 – PX 233153.

Habitat.

All specimens of Niphargus primoricus sp. nov. were collected from the deep layers of pebble beach habitats along the northern Black Sea coastline (Fig. 1 A View Figure 1 ). This species inhabits freshwater environments, such as small rivers, streams, and springs, which ooze in the lower layers of coastal pebbles near the edge of the sea (Fig. 1 C – F View Figure 1 ). These biotopes are common along the northern coast of the Black Sea, alternating with rocky outcrops and small sandy beaches. Also, several individuals of this species have been found in hyporhean habitats under thick layers of pebbles in the small mountain river Kuapse (near the village of Nizhnyaya Mamedka), which flows into the Black Sea.

Distribution.

The species is currently found along the northern coastline of the Black Sea, from the mouth of the Ashamba River ( 44°34'35.9"N, 37°58'48.3"E) to the Khosta River ( 43°30'33.9"N, 39°52'07.0"E) (the type locality) (see Fig. 1 View Figure 1 ), with the most distant localities separated for 190 km.

Etymology.

The new species is named after its unique habitat and distribution along the northern Black Sea coastline; primoricus (Russian) meaning “ living close to the sea shore ”.

Taxonomic remarks.

Niphargus primoricus sp. nov. clearly belongs to the European “ stygius – longicaudatus ” species group (Fig. 1 View Figure 1 ) according to the molecular genetic analysis, closely related to Niphargus tarkhankuticus Marin, Turbanov, Prokopov & Palatov, 2022 from Tarkhankut Peninsula (Crimea), as well as N. longicaudatus (A. Costa, 1851) , N. aitolosi Ntakis, Anastasiadou, Zakšek & Fišer, 2015 , N. cvijici S. Karaman, 1950 , N. frasassianus G. Karaman, Borowsky & Dattagupta, 2010 , N. pasquinii Vigna-Taglianti, 1966 , N. sibillianus G. Karaman, 1984 , N. sodalis G. Karaman, 1984 , N. timavi S. Karaman, 1954 , and N. versluysi S. Karaman, 1950 , known in the Apennine and Balkan Peninsulas (see Karaman 1986, 1989; Marin et al. 2022). These species have distally bluntly produced anterodistal lobe of the head; the presence of two dorsolateral spines on urosomite III; the presence of two hooks in retinacles; uropod I with different sized rami, with endopodite ramus usually larger than exopodite; rami of uropod I with characteristic thin-flexible setae; and bluntly rounded posteroventral corners of epimeral plates.

Together with Crimean N. tarkhankuticus and two undescribed species from Crimea (Staryi Krym) and northern Türkiye (Akgüney, Sinop) (IM, unpublished data) (see Fig. 1 View Figure 1 ), the new species forms a geographically local Pontic (of the Black Sea area) group of species, which has been named as the “ tarkhankuticus ” ingroup (see Marin et al. 2022). However, the new species can be separated from N. tarkhankuticus by several minute morphological features, such as 1) almost straight posterior margin of epimeral plate II and triangularly produced posterolateral angle of epimeral plate III; 2) significantly longer distal spines on lobes of telson; and 3) strongly spinulated protopodites of uropods I and II. At the same time, morphological similarity in most other morphological features clearly indicates a very close phylogenetic relationship between these species.

To distinguish from the related European species, namely N. longicaudatus , N. aitolosi , N. cvijici , N. frasassianus , N. pasquinii , N. sibillianus , N. sodalis , N. timavi and N. versluysi , see Marin et al. (2022), where a detailed morphological comparison is given with N. tarkhankuticus , which is phylogenetically and morphologically very close to the new species (see above) ..

Molecular phylogenetic approach.

The molecular genetic analysis (Fig. 1 B View Figure 1 ) clearly confirmed the monophyly (Bayesian – PP = 1.00; ML – BS = 95 %) of the studied lineage, including Niphargus primoricus sp. nov., N. tarkhankuticus , and two undescribed species from the coastal habitats of the Black Sea (see Fig. 1 B View Figure 1 ; Table 2 View Table 2 ).

The interspecific genetic differences between the studied related Niphargus species mostly vary from 12 % to 13 % (see Table 1 View Table 1 ).

The intraspecific genetic divergence between the individuals from recently discovered locations (the most remote of them are separated by a distance of 190 km) (see Table 1 View Table 1 ) of Niphargus primoricus sp. nov. ( n = 17) is very low, with the interspecific uncorrected pairwise distances ( p - distances) estimated as ~ 0.8 % (0.008 ± 0.001 substitutions per 100 nucleotide positions).

ZooBank taxon ID.

The electronic version of this article in Portable Document Format will represent a published work according to the International Commission on Zoological Nomenclature ( ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank Life Science Identifiers ( LSID) for this publication is: https://zoobank.org/ D09561CD-8A55-4127-999B-FEC5C07237D0. The online version of this work is archived and available from the following digital repositories: ZooKeys, PubMed Central and CLOCKSS. The LSID for the new species, Niphargus primoricus sp. nov., is https://zoobank.org/ 3ED10492-D4D5-420A-A2EF-9511C8E17C2C.