The remarkable Ponto-Caspian amphipod diversity of the lower Durso River (SW Caucasus) with the description of Litorogammarus dursi gen. et sp. nov. Author Marin, Ivan 0000-0003-0552-8456 A. N. Severtsov Institute of Ecology and Evolution of RAS, 119071, Moscow, Russia & coralliodecapoda @ mail. ru; vanomarin @ yahoo. com; https: // orcid. org / 0000 - 0003 - 0552 - 8456 coralliodecapoda@mail.ru Author Palatov, Dmitry 0000-0002-8826-9316 A. N. Severtsov Institute of Ecology and Evolution of RAS, 119071, Moscow, Russia & triops @ yandex. ru; https: // orcid. org / 0000 - 0002 - 8826 - 9316 triops@yandex.ru Author Copilaș-Ciocianu, Denis 0000-0002-6374-2365 Laboratory of Evolutionary Ecology of Hydrobionts, Nature Research Centre, Vilnius, Lithuania & denis. copilas-ciocianu @ gamtc. lt; https: // orcid. org / 0000 - 0002 - 6374 - 2365 denis.copilas-ciocianu@gamtc.lt text Zootaxa 2023 2023-06-06 5297 4 483 517 http://dx.doi.org/10.11646/zootaxa.5297.4.2 journal article 53675 10.11646/zootaxa.5297.4.2 7a696b67-414f-408d-a282-70f965926705 1175-5326 8009123 6E7C1770-D107-4FF7-A2DC-F2A693E581F1 Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. Figs 9–13 Echinogammarus karadagiensis Grintsov, 2009 : e-23, fig. 1 [ type locality—Batiliman, Crimea,]. Material examined. 10 ÔÔ , 10♀♀ , LEMMI — Northeastern Black Sea , Russian Federation , southwestern Caucasus , Krasnodar Krai , Novorossiysk area , Durso village , pebble beach, 44°40’41.1”N 37°33’44.1”E , under the upper layer of pebble and stones, with hand net , coll. Palatov D.M. & Marin I.N. , 20.07.2021 . Diagnosis. Head with oblique anteroventral lobe. Pleon with urosomite I armed with a pair of submedian posterior long simple spines; urosomite II with 1 marginal long spine on each side and a pair of median long spines; urosomite III with 1 long and 1small marginal spines of each side. Antenna I with 3-segmented accessory flagellum. Antenna II without calceoli both in males and females. Gnathopods I–II densely covered with long plumose setae. Pereopods V–VII : basis (article 2) with convex dorsal margin, especially in PV, and well-marked ventral lobes. Epimeral plates with sharp but not produced posteroventral angles. TABLE 3. Morphological comparison of the species belonging the genus Litorogammarus gen. nov. Asterisk denotes sequences obtained in this study.

L. mazestiensis	L. karadagiensis	L. dursi sp. nov.	sp. from Caspian Sea
GenBank Accession nos.	OP466441, OP466428*	ON258047, ON2580951	OQ407693– OQ407694*	ON258059 ON2581201
Mouthparts	Normal	Normal	Specialized	Normal
Head anterolateral lobe	Oblique, straight	Oblique, straight	Rounded	Oblique, straight
AI vs. AII	Longer	Subequal	Longer	Longer
AI acc. flagellum #art.	5	4	8	4
AII curly setae	Yes	Yes	Yes	Yes
AII calceoli	No	No	No	No
Setation GI–II	Normal	Long and plumose setae	Normal	Normal
Setation PIII–IV	Sparse, straight	Sparse, straight	Sparse, straight	Sparse, straight
Urosomite I armature	One middle group of 2 setae	One middle group of 2 spines and setae	Several groups of spines and setae	Several groups of spines and setae
UIII exopod outer margin	Weakly setose	Weakly setose	Weakly setose	Weakly setose
Epimeral plate III	Pointed	Weakly pointed	Weakly pointed	Weakly pointed
Telson lobes shape	Longer than broad, not abruptly tapering	Longer than broad, not abruptly tapering	Longer than broad, not abruptly tapering	Longer than broad, not abruptly tapering

1 sequences obtained in Copilaș-Ciocianu et al. 2022. Short description. Head with oblique anteroventral lobe ( Fig. 13 a ). Eye reniform, well pigmented. Pleon ( Fig. 13 f ) with urosomite I bearing a pair of submedian posterior long simple spines; urosomite II with 1 marginal long spine on each side and a pair of median long spines; urosomite III with 1 long and 1small marginal spines of each side ( Fig. 13 f ). Antenna I smooth, non-setose, with 3-segmented accessory flagellum, with small aesthetascs ( Fig. 9 a, b ). Antenna II slightly shorter that AI, with long ventral setae, without calceoli both in males and females ( Fig. 9 c ). Upper lip ( labrum ) with convex distal part ( Fig. 10 a ). Lower lip ( labium ) with mostly reduced inner lobes ( Fig. 10 b ). Mandible with outer lobe subequal to inner lobe, not expanding distally, with short incisor teeth ( Fig. 10 c–f ). Maxilla I with outer plate bearing a marginal row of hairbrush-like setae, with outer lobe subequal to inner lobe, distal segment of palp expanding distally ( Fig. 10 g ). Maxilla II with outer lobe equal to inner lobe, bluntly expanding distally ( Fig. 10 i ). Maxilliped with outer and inner plates wide, distally bluntly rounded, with long plumose setae ( Fig 10 j ). Gnathopod I shorter and wider than GnII, not sexually dimorphic, bearing long plumose setae, propodus (palm) with convex slightly oblique palmar margin ( Fig. 9 d ). Gnathopod II not sexually dimorphic, bearing long plumose setae, subrectangular and elongated, about 3 – 4 times as long as wide, with oblique palmar margin ( Fig. 9 e ). Pereopods V–VII with relatively stout and robust segments armed with short strong spines, basis (article 2) with convex dorsal margin, especially in PV, and well-marked ventral lobes; dactylus stout ( Fig.11 ). Pleopods with 2 elongated hooks and 1–2 thick bristles in retinacules ( Fig. 12 f ). Uropod III similar in male and females, robust, with outer ramus broad, about 4 times as long as wide, with reduced distal article furnished with numerous long simple distal setae ( Fig. 12 i ). Epimeral plates with sharp but not produced posteroventral angles ( Fig. 12 a–c ). Telson entirely clefted, with teardrop-shaped lobes bearing clusters of strong stout apical and submedian spines ( Fig. 12 d ). Coloration. Body and appendages translucent. Eyes cornea silver or brown. Body size. The largest collected ♀ has tbl. 4.0 mm; the largest collected Ô has tbl. 4.0 mm. GenBank accession number. ON258047, ON258095 (Copilaș-Ciocianu et al. 2022). FIGURE 9. Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. , ♀: a —antenna I; b —accessory flagellum of antenna I; c —antenna II; d —gnathopod I; e— gnathopod II. FIGURE 10. Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. , ♀: a —upper lip; b —lower lip; c —left mandible; d— same, incisor process and pars incisiva; e —right mandible; f— same, incisor process and pars incisiva; g —left maxilla I; h— palp of right MxI; i— maxilla II; j —maxilliped. FIGURE 11. Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. , ♀: 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 12. Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. , ♀, a–c —epimeral plates I–III; d —telson I; e— pleopod I; f— retinacula of pleopod I; g —uropod I; h —uropod II; i— uropod III. FIGURE 13. Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. , ♀ a —head; b —urosomal segments, lateral view; c— gnathopod I; d —chela of GnI; e —palmar margin of chela of GnI; f— gnathopod II; g —chela of GnII; h —palmar margin of chela of GnII. Habitat and distribution. Widely distributed species presently known along the northeastern Black Sea coast, from Batiliman, Laspi Bay ( type locality), Karadag Bay ( Grintsov, 2009 , 2016 ) to Durso (present study). Small pebble-dwelling species, living together with Ch. oliviiformis under the upper layer of the pebble, boulder and stones, where both species forms sufficiently large aggregations of heterosexual and different-aged individuals. For the detailed biological features see Grintsov (2016) . Taxonomic remarks. The complete re-description of the species using SEM micrographs is presented by Grintsov (2022) . Litorogammarus karadagiensis ( Grintsov, 2009 ) comb. nov. can be easily identified among congeners and Echinogammarus -like taxa by long plumose setae densely covering mouthparts and gnathopods, which are actually unique within the Ponto-Caspian amphipods. The species can be also easily identified by 3- segmented accessory flagellum of AII and convex dorsal margin of basis of PV.