Diasynurella kiwi Marin et Palatov, 2023

Palatov, Dmitry M. & Marin, Ivan N., 2023, Diversity of the Caucasian genus Diasynurella Behning, 1940 (Amphipoda: Crangonyctidae) with description of four new species, Arthropoda Selecta 32 (1), pp. 23-55 : 25-32

Diasynurella kiwi Marin et Palatov sp.n.

Figs 1–5 .

MATERIAL EXAMINED. Holotype $ (bl. 3.0 mm), ZMMU Mb-1248 Russian Federation, Ciscaucasia, Rostov Oblast’, Rostov-on-Don , Proletarskiy district , 47°13′59.9″N 39°47′00.1″E, about 40 m a.s.l., small spring on shore of Kiziterinka river , hand net sampling, 18 May 2022, coll. D. Palatov et I. Marin. Paratypes 1$ (bl. 3.0 mm), 1# (bl. 2.0 mm), ZMMU Mb-1249, same locality and data as for holotype .

Additional material: 4$$, LEMMI, same locality and data as for holotype .

ETYMOLOGY. The name of the species comes from the endemic New Zealand flightless ground-dwelling bird Apteryx australis Shaw, 1813 , usually called “ kiwi ”, which also bears only single egg, occupying most of the female’s body. Females of Diasynurella kiwi Marin et Palatov sp.n., similar to other representatives of the genus Diasynurella , usually bears only two large eggs, but outwardly they look like a single mass ( Fig. 6 ), resembling one large egg of this unusual bird. Also similar to this bird is due to their endemicity, and the inability of the crustacean to leave its spring or group of nearby springs (“island”) and spread over long distances (flightless). Thus, the inability to fly (escape) to another place closer these crustaceans to kiwi birds, and we would like to keep this name for one of the species of the genus Diasynurella .

DESCRIPTION. Female. Body ( Fig. 1 ): moderately stout; largest collected $ has bl. 3.0 mm. Head with wide rounded and little concave anteroventral lobe ( Fig. 11 b ).

Antenna I ( Fig. 2 a ) about 55% of body length, about 2.1X longer than antenna II; primary flagellum with 13 segments, with aesthetascs on distal segments; accessory flagellum 2-segmented, distal segment about 3.1X shorter than basal one ( Fig. 2 b ).

Antenna II ( Fig. 2 c ): gland clone distinct, distally pointed; peduncle about 2.0–2.3X longer than flagellum, with robust setae tightly covering segments III–IV; peduncle of segment IV about 1.1X longer than segment V; flagellum 5- segmented.

Mandible ( Fig. 3 c–f ): left mandible ( Fig. 3 c, d ) incisor 5-dentate, lacinia mobilis 5-dentate, with 3–4 robust plumose accessory setae; molar process with single seta. Right mandible ( Fig. 3 e, f ) incisor 4-dentate, lacinia mobilis toothed, triturative, lobes with numerous protuberances; underlying with row of three robust plumose setae; molar process similar to left mandible. Palp 3-segmented, segment II with four–seven setae; segment III about 2.5X longer than wide, with seven–eight separate D-setae, single C-seta, single B-seta and three–four separate E-setae ( Fig. 3 c, e ).

Labrum (upper lip) ( Fig. 3 a ): oval, apical margin with numerous small fine setae.

Labium (lower lip) ( Fig. 3 b ): inner lobes feebly developed.

Lateralia with eight strong pectinate setae.

Maxilla I ( Fig. 3 g ): inner plate with four plumose marginal setae, outer plate with seven apical comb-spines; palp 2-segmented, distal segment pubescent, about 3X of basal segment, apical margin of distal segment with seven simple setae.

Maxilla II ( Fig. 3 h ): inner and outer plates covered in pubescent setae, subequal in length; outer plate weakly narrowing distally, with nine apical setae; inner plate narrowing explicitly distally, with group of dense short setae on apex, with oblique row of two short plumose setae.

Maxilliped ( Fig. 3 i ): inner plate much shorter than outer plate, with four spines and single simple seta apically, and two–three simple setae laterally; outer plate narrow, with row of 12–14 medial stiff simple setae of different length; palp quadriarticulate, article I with two simple setae on inner margin, article II with row of 13–15 simple setae on inner margin and without setae on outer margin, article III sub-quadrate; dactylus with single seta on outer margin and without setae at inner margin, nail long, slender, with two thin setae at hinge.

Gnathopod I ( Fig. 2 d, e ): smaller than GnII; coxal plate suboval, slightly narrowing distally, with rounded corners and with four apical and numerous facial setae, width/depth ratio 0.66–0.67/1; basis width/length ratio is 0.38/1, without setae on anterior margin, two long setae on inner face and three–five long setae on posterior margin; merus with eight– nine distal setae; carpus is 0.53X of basis and subequal of propodus in length, with six–eight serrated setae in inner margin and three simple setae in outer margin; propodus 1.5X longer than broad, with one–three simple setae in anterior margin and five serrated single setae in posterior margin; distal margin of palm ( Fig. 2 e ) almost straight, slightly oblique, with double row of four inner and three outer robust setae; palmar groove (depression) feebly developed, with two inner and two outer robust setae; dactylus with single outer seta.

Gnathopod II ( Fig. 2 f, g ): coxal plate sub-rectangular or subovate, with four apical and numerous facial setae, width/ depth ratios is 0.6/1; basis width/length ratio is 0.3/1, with several (two–three) long setae inserted along posterior margin and with two long simple setae in anterior margin; ischium with single short simple seta; merus with four distal setae; carpus is 0.62X of length of basis and 0.96X of propodus, with two anterior simple setae and three groups of plumose posterior setae; propodus 2.4X longer than broad, with single simple anterior seta, four superior medial, three inferior medial and four groups of posterior setae; palm oblique with double row of four inner and three outer robust setae of different size; palm groove (depression) feebly developed, palmar corner ( Fig. 2 g ) with two strong palmar spiniform setae, single supporting spiniform seta on inner surface; dactylus with single seta along anterior margin and few short setae along inner margin.

Pereopod III ( Fig. 4 a ): coxal plate oval or subrectangular, with three apical and numerous facial setae, width/depth ratio is 0.6/1; basis about 4.5X as long as wide, with long anterior and posterior simple setae; merus about 0.65X of basis, about 1.70X of carpus and about 1.12X of propodus in length; carpus about 0.66X of propodus in length; dactylus ( Fig. 4 b ) about 0.40X of propodus, with single plumose seta on outer margin and single additional spine accompanying with seta along ventral margin.

Pereopod IV ( Fig. 4 c ): subequal to PIII in length; coxal plate expanded and broadly convex distally, posterior margin with shallow excavation, distal margin with eight–nine apical short setae and numerous facial setae, width/depth ratio is 0.94/1; basis about 4.6X as long as wide, with long anterior and posterior simple setae; merus about 0.63X of basis, about 1.67X of carpus and about 1.05X of propodus in length; carpus about 0.63X of propodus in length; dactylus ( Fig. 4 d ) about 0.36X of propodus, with plumose seta on outer margin and single additional spine accompanying with seta along ventral margin.

Pereopods V, VI, VII with length ratio 1/1.20/1.26.

Pereopod V ( Fig. 4 e ): coxal plate large, bilobate, with distinct anterior and posterior lobes; posterior and anterior lobes with 1 margin simple seta each, with numerous facial setae; basis about 1.60X as long as wide, with numerous facial setae, posterior margin slightly convex, armed with 6 shallow serrations, with distinct distal corner, anterior margin with five split-tipped robust and four distal setae; merus about 0.63X of basis, 0.75X of carpus and 0.90X of propodus in length; dactylus ( Fig. 4 f ) approximately 0.44X of propodus, with single plumose seta on outer margin and 1 additional spine accompanying with seta along ventral margin.

Pereopod VI ( Fig. 4 g ): coxal plate bilobate, with distinct posterior and vestigial anterior lobes; anterior lobe without setae, posterior lobe with single margin seta, each with numerous facial setae; basis about 1.60X as long as wide, with numerous facial setae, posterior margin convex, armed with five shallow serrations, anterior margin with five split-tipped robust and three distal setae; merus about 0.70X of basis, 0.83X of carpus and 0.82X of propodus in length; dactylus ( Fig. 4 h ) approximately 0.41X of propodus, with single plumose seta on outer margin and single additional spine accompanying with seta along ventral margin.

Pereopod VII ( Fig. 4 i ): coxal plate small, semi-lunar, with single posterior seta; basis about 1.56X as long as wide, with numerous facial setae, posterior margin convex, armed with eight serrated setae, with distal corner; anterior margin with four split-tipped robust and three distal setae; merus about 0.57X of basis, about 0.90X of carpus and about 0.89X of propodus in length; dactylus ( Fig. 4 j ) approximately 0.43X of propodus in length, with single plumose seta on outer margin and single additional spine accompanying with single seta along ventral margin.

Gills, brood plates ( Fig. 4 ): coxal gills on somites II–VI, somites V–VIII with lanceolate sternal gill on each. Coxal gills of pereiopods II–VI ovoid, gills/bases ratios are 0.83/1, 0.72/1, 0.58/1, 0.41/1 and 0.45/1, respectively.

Pleopods ( Fig. 5 e ): pleopod I peduncle with two coupling hooks in retinacula, without lateral setae; outer and inner rami with six and seven segments, respectively; basal segment of outer ramus with single clothes-pin seta. Pleopods II–III with peduncle bearing two coupling hooks in retinacula ( Fig. 5 f ), without setae; outer and inner rami with six segments; basal segment of outer ramus with single clothes-pin seta.

Epimera. Epimeral plate I ( Fig. 5 a ) weakly produced distally, almost straight, pointed, ventral margin with one spine, posterior margin convex, with singlee seta. Epimeral plate II ( Fig. 5 b ) distally produced and sharply pointed, ventral margin armed with single spine, posterior margin oblique, without setae. Epimeral plate III ( Fig. 5 c ) weakly produced distally, almost straight, and slightly pointed, ventral margin armed with single spine, posterior margin slightly convex, with single seta.

Urosomites completely free ( Figs 1 , 11 a ).

Uropod I ( Fig. 5 g ): peduncle about 4.3X as long as wide, with dorsoexternal row of three thin short spines and single subdistal short spine; exopodite subequal of endopodite in length; endopodite not paddle-like, with three dorsal, single ventrolateral and five apical spines; exopodite with three dorsal and five apical spines.

Uropod II ( Fig. 5 h ): peduncle about 2.7X as long as wide, subequal of endopodite in length, with three short dorsoexternal spines; exopodite about 0.9X of endopodite in length, with four dorsal and five apical robust spines; endopodite with three dorsal and five apical robust spines.

Uropod III ( Fig. 5 i ): uniramous, peduncle cone-shaped, about 1.6X as long as wide, without terminal “pointed knob” and single simple seta on lateral margin and single spine on apical margin; peduncle about 0.6X of ramus in length; inner margin of ramus armed with two single spines, outer margin of ramus armed of two groups of spines with two spines each, apical margin armed with three spines.

Telson ( Fig. 5 d ): clearly expanding distally, with narrow lobes, elongate, 0.57X as long as broad, significantly shorter as uropod III; apical margin cleft about 0.65X of total length; with five apical spines and two additional submarginal plumose setae on each lobe.

REMARKS. Sexual dimorphism is feebly marked; males are slightly smaller in size ( Fig. 1 ); with small and elongated calceoli on peduncle and flagellum of antenna II; and slightly elongated plam of gnathopods I–II.

COLORATION. The body and appendages unpigmented, without well-developed pigmented eyes.

GENBANK ACCESSION NUMBERS. OQ533591, OQ533592.

TAXONOMIC REMARKS. Most phylogenetically basal and morphologically distinct species within the genus. Diasynurella kiwi Marin et Palatov sp.n. can be clearly separated from all other species of the genus Diasynurella , by the following features: 1) all urosomites completely free vs. urosomites II–III fused in other species; 2) uropod III is much longer than telson vs. uropod III is subequal to telson in length or shorter; 3) inner plate of maxilla I with four plumose marginal setae vs. inner plate of maxilla I with two plumose marginal setae; 4) telson clearly expanding distally, with narrow lobes vs. telson subrectangular, with wide lobes.

DISTRIBUTION AND ECOLOGY. Currently, the species is known only from single spring on the slope of the Kiziterinka River in the Proletarskiy district (Nakhichevan) within the borders of the city of Rostov-on-Don. We assume that the species may live in other nearby springs, which apparently have one pool of catchment. At the same time, the collecting this species is rather difficult due to its very small size (about 2.5–3 mm of body length for adults), as well as habitat in the thickness of pebbles covering the bottom of springs and wells. Other stygobiotic amphipods found in the same spring are Synurella odessana (Martynov, 1919) and undescribed species of the genus Niphargus Schiödte, 1849 ( Niphargidae ) [Marin, Palatov, in press].

Figures

Fig. 1. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don; general view. Рис. 1. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, город Ростов-на-Дону; обЩий вид.

Fig. 2. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don: a — antenna I; b — accessory flagellum of antenna I; c — antenna II; d — gnathopod I; e — distoventral palmar margin of chela of GnI; f — gnathopod II; g — distoventral palmar margin of chela of GnII. Рис. 2. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, Ростов-на-Дону: a — антенна I; b — вспомогатель- ный жгутик антенны I; c — антенна II; d — гнатопода I; e — дистовентральный край ладони клеШни GnI; f — гнатопода II; g — дистовентральный край ладони клеШни GnII.

Fig. 3. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don: a — labrum (upper lip); b — labium (lower lip); c — left mandible; d — same, incisor process and pars incisiva; e — right mandible; f — same, incisor process and pars incisiva; g — maxilla I; h — maxilla II; i — maxilliped. Рис. 3. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, Ростов-на-Дону: a — верхнЯЯ губа; b — нижнЯЯ губа; c — леваЯ мандибула; d — то же самое, реЗцовый отросток и pars incisiva; e — праваЯ мандибула; f — то же самое, реЗцовый отросток и pars incisiva; g — максилла I; h — максилла II; i — максиллипед.

Fig. 4. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don: 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. Рис. 4. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, Ростов-на-Дону: a — переопода III; b — дактилус PIII; c — переопода IV; d — дактилус PIV; e — переопода V; f — дактилус PV; g — переопода VI; h — дактилус PVI; i — переопода VII; j — дактилус PVII.

Fig. 5. Diasynurella kiwi Marin et Palatov sp.n., Russia, Rostov Oblast’, Rostov-on-Don: a — epimeral plate I; b — epimeral plate II; c — epimeral plate III; d — telson; e — pleopod III; f — hooks of retinacula of pleopod II; g — uropod I; h — uropod II; i — uropod III. Рис. 5. Diasynurella kiwi Marin et Palatov sp.n., РоссиЯ, РостовскаЯ область, Ростов-на-Дону: a — ЭпимеральнаЯ пластинка I; b — ЭпимеральнаЯ пластинка II; c — ЭпимеральнаЯ пластинка III; d — тельсон; e — плеопода III; f — крючки ретнакулы плеопод II; g — уропода I; h — уропода II; i — уропода III.

Fig. 6. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: general view of freshly fixed specimens. The arrows indicate eggs. Рис. 6. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: обЩий вид свежефиксированных обраЗцов. Стрелки укаЗывают на Яйцо.

Fig. 11. Diasynurella kiwi Marin et Palatov sp.n. (a, b, h) and D. dzhamirzoevi Palatov et Marin sp.n. (c–g): a, c — urosomal segments, lateral view; b, d — head; e — gnathopod I; f — chela of gnathopod I; g, h — dactyli of ambulatory pereiopods (legs). Рис. 11. Diasynurella kiwi Marin et Palatov sp.n. (a, b, h) и D. dzhamirzoevi Palatov et Marin sp.n. (c–g): a, c — уросомальные сегменты, вид сбоку; b, d — голова; e — гнатопод I; f — клеШнЯ гнатоподы I; g, h — дактилусы амбулаторных переопод (ног).