Diasynurella cavatica Palatov et Marin, 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 : 40-45

Diasynurella cavatica Palatov et Marin sp.n.

Figs 12–15 , 20 .

MATERIAL EXAMINED. Holotype $ (bl. 4.0 mm), ZMMU Mb-1252, Southern slope of the Great Caucasian Ridge , Colchis lowland, Georgia, Samegrelo-Zemosvaneti, Garakha cave, 42°31′ 47.5″N, 42°10′39.2″E, about 200 m a.s.l., hand net sampling, 3 February 2017, coll. D. Palatov.

ETYMOLOGY. The species is named after its cave-dwelling lifestyle, which is currently unique for the genus.

DESCRIPTION. Female. Body: moderately stout, largest collected $ has bl. 4.0 mm. Head with wide rounded and little concave or straight anteroventral lobe ( Fig. 20 b ).

Antenna I ( Fig. 12 a ) about 55% of body length, about 2.2X longer than antenna II; primary flagellum with twelve segments, with aesthetascs on distal segments; accessory flagellum 2-segmented, distal segment about 2.0–4.4X shorter than basal one ( Fig. 12 b ).

Antenna II ( Fig. 12 c ): gland clone distinct, distally pointed; peduncle about 2.5X longer than flagellum, with robust setae tightly covering segments III and IV; peduncle of segment IV about 1.1–1.2X longer than segment V; flagellum 7-segmented.

Mandible ( Fig. 13 d–g ): left mandible ( Fig. 8 c, d ) incisor 5-dentate, lacinia mobilis 5-dentate, with three robust plumose accessory setae; molar process with a single seta. Right mandible ( Fig. 8 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 six – seven setae; segment III about 3.1–3.2X longer than wide, with seven–eight separate D-setae, single B-seta and four separate E-setae ( Fig. 13 e, g ).

Labrum (upper lip) ( Fig. 13 a ): oval, apical margin with numerous small fine setae.

Labium (lower lip) ( Fig. 13 b ): inner lobes feebly developed.

Lateralia ( Fig. 13 c ) with eight strong pectinate setae.

Maxilla I ( Fig. 13 h ): inner plate with two plumose marginal setae, outer plate with seven apical comb-spines; palp 2-segmented, distal segment pubescent, about 3.0X of basal segment, apical margin of distal segment with seven simple setae.

Maxilla II ( Fig. 13 i ): inner and outer plates covered in pubescent setae, subequal in length; outer plate weakly narrowing distally, with eleven apical setae; inner plate narrowing explicitly distally, with group of dense short setae on apex, with an oblique row of two short plumose setae.

Maxilliped ( Fig. 13 j ): 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 14–16 medial stiff simple setae of different length; palp quadriarticulate, article I with two simple setae on inner margin, article II with row of 16–18 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 one or two thin setae at hinge.

Gnathopod I ( Fig. 12 d, e ): smaller than GnII; coxal plate subtrapezoidal or suboval, slightly narrowing distally, with rounded corners and with five apical and numerous facial setae, width/depth ratio 0.60/1; basis width/length ratio is 0.35/1, with two short setae on anterior margin, two long setae on inner face and four long setae on posterior margin; merus with nine–ten distal setae; carpus is 0.60X of basis and 0.87X of propodus in length, with ten serrated setae in inner margin and eight simple setae in outer margin; propodus 1.70X longer than broad, with four simple setae in anterior margin and nine serrated single setae in posterior margin; distal margin of palm ( Fig. 12 e ) distinctly or slightly oblique, with double row of four inner and three outer robust setae; palmar groove (depression) feebly developed, with two inner and three outer robust setae; dactylus with single outer seta.

Gnathopod II ( Fig. 12 f, g ): coxal plate subovate, with five apical and numerous facial setae, width/depth ratios is 0.55/1; basis width/length ratio is 0.30/1, with several (three– four) long setae inserted along posterior margin and with four short simple setae in anterior margin; ischium with single short simple seta; merus with three distal setae; carpus is 0.60X of length of basis and 0.82X of propodus, with five anterior simple setae and five groups of plumose posterior setae; propodus 2.4X longer than broad, with four simple anterior setae, five superior medial, four inferior medial and six groups of posterior setae; palm distinctly oblique with double row of five inner and six outer spiniform setae of different size; palm groove (depression) feebly developed, palmar corner ( Fig. 12 g ) with three strong palmar spiniform setae, three supporting bifurcate setae on inner surface; dactylus with single seta along anterior margin and few short setae along inner margin.

Pereopod III ( Fig. 14 a ): coxal plate oval or sub-rectangular, with six apical and numerous facial setae, width/depth ratio is 0.6/1; basis about 4.3X as long as wide, with long anterior and posterior simple setae; merus about 0.63X of basis, about 1.40X of carpus and about 1.07X of propodus in length; carpus about 0.77X of propodus in length; dactylus ( Fig. 14 b ) about 0.46X of propodus, with single plumose seta on outer margin and an additional spine accompanying with singleseta along ventral margin.

Pereopod IV ( Fig. 14 c ): subequal to PIII in length; coxal plate expanded and broadly convex distally, posterior margin with a shallow excavation, distal margin with eleven apical short setae and numerous facial setae, width/depth ratio is 0.86/1; basis about 4.8X as long as wide, with long anterior and posterior simple setae; merus about 0.66X of basis, about 1.50X of carpus and about 1.22X of propodus in length; carpus about 0.81X of propodus in length; dactylus ( Fig. 14 d ) about 0.42X of propodus, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Pereopods V, VI, VII with length ratio 1/1.20/1.08.

Pereopod V ( Fig. 14 e ): coxal plate large, bilobate, with distinct anterior and posterior lobes; posterior and anterior lobes with single margin simple seta each, with numerous facial setae; basis about 1.38X as long as wide, with numerous facial setae, posterior margin slightly convex, armed with 11 shallow serrations, with distinct distal corner, anterior margin with ten split-tipped robust and four distal setae; merus about 0.65X of basis, 1.05X of carpus and 1.14X of propodus in length; dactylus ( Fig. 14 f ) approximately 0.48X of propodus, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Pereopod VI ( Fig. 14 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 1.38X as long as wide, with numerous facial setae, posterior margin convex, armed with 11 shallow serrations, anterior margin with six split-tipped robust and three distal setae; merus about 0.69X of basis, subequal of carpus and 0.90X of propodus in length; dactylus ( Fig. 14 h ) approximately 0.40X of propodus, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Pereopod VII ( Fig. 14 i ): coxal plate small, semi-lunar, with single posterior seta; basis about 1.10X as long as wide, with numerous facial setae, posterior margin convex, armed with 11 serrated setae, with distal corner; anterior margin with six split-tipped robust and three distal setae; merus about 0.56X of basis, about 1.08X of carpus and about 0.90X of propodus in length; dactylus ( Fig. 14 j ) approximately 0.40X of propodus in length, with single plumose seta on outer margin and an additional spine accompanying with single seta along ventral margin.

Gills, brood plates ( Fig. 14 ): coxal gills on somites II– VI, somites V–VIII with lanceolate sternal gill on each. Coxal gills of pereopods II–VI ovoid, gills/bases ratios are 0.84/1, 0.78/1, 0.82/1, 0.68/1 and 0.60/1, respectively.

Pleopods ( Fig. 15 e, f ): pleopods I and II peduncles with two coupling hooks in retinacula ( Fig. 10 h ), without lateral setae; outer and inner rami with 8 and 10 segments, respectively; basal segments of outer ramus with single clothes-pin seta. Pleopod III peduncle with two coupling hooks in retinacula, without setae; outer and inner rami with 7 and 8 segments, respectively; basal segment of outer ramus with single clothes-pin seta.

Epimera. Epimeral plate I ( Fig. 15 a ) weakly produced distally, pointed, ventral margin without spines, posterior margin oblique, with one seta. Epimeral plate II ( Fig. 15 b ) distally produced and sharply pointed, ventral margin armed with two spines, posterior margin slightly oblique, with single seta. Epimeral plate III ( Fig. 15 c ) subtrapezoidal, blunted distally, ventral margin armed with three spines, posterior margin slightly oblique, with single seta.

Urosomites fused partially: Urosomite I completely free, urosomites II–III fused, with slightly noticeable suture ( Fig. 20 a ).

Uropod I ( Fig. 15 g ): peduncle about 3.2X as long as wide, with dorsoexternal row of four thin spines, single subdistal short thin spine and single dorsointernal thin spine; exopodite about 0.9X of endopodite in length; endopodite not paddle-like, with four dorsal, single dorsolateral and five apical thin spines; with three dorsal, four dorsolateral and five apical thin spines.

Uropod II ( Fig. 15 h ): peduncle about 1.7X as long as wide, subequal of endopodite in length, with three dorsoexternal long spines; exopodite about 0.88X of endopodite in length, with four dorsal, single dorsolateral and five apical robust spines; endopodite with five dorsal, single dorsolateral and five apical robust spines.

Uropod III ( Fig. 15 i ): uniramous, peduncle cone-shaped, about 1.4X as long as wide, without terminal “knob”, single simple seta on lateral margin and single spine on apical margin; peduncle about 1.4X of ramus in length; inner margin of ramus with single simple seta, outer margin of ramus armed with two spines, apical margin armed with four spines.

Telson ( Fig. 15 d ): slightly narrowing distally, slightly elongated, 0.75X as long as broad, subequal with uropod III in length; apical margin cleft about 0.48X of total length; with four apical spines and two additional submarginal plumose setae on each lobe.

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

GENBANK ACCESSION NUMBERS. OQ534005, OQ534006.

TAXONOMIC REMARKS. The species can be most easily separated from D. waschuschtii by the following features: 1) ramus and peduncle of uropod III approximately equal in length ( Fig. 15 i ) vs. ramus is significantly smaller than peduncle in length [ Behning, 1940, fig. 17n]; 2) rami of uropod III with two separate spines on lateral margins ( Fig. 15 i ) vs. rami of uropod III without lateral spines [ Behning, 1940, fig. 17n]; 3) epimeral plates II–III with two and three thin spiniform setae on ventral margin, respectively ( Fig. 15 b, c ) vs. epimeral plates II–III with single thin seta on ventral margin each [ Behning, 1940, fig. 18j].

The species can be most easily separated from Diasynurella kiwi Marin et Palatov sp.n., by the following features: 1) urosomites II and III completely fused ( Fig. 20 a ) vs. all urosomites completely free ( Fig. 11 a ); 2) uropod III is subequal to telson in length ( Fig. 20 a ) vs. uropod III is much longer than telson ( Fig. 11 a ); 3) inner plate of maxilla I with two plumose marginal setae ( Fig. 13 g ) vs. inner plate of maxilla I with four plumose marginal setae ( Fig. 3 g ).

The species can be most easily separated from Diasynurella dzhamirzoevi Palatov et Marin sp.n., by the following features: 1) apical margin cleft of telson is about half of its total length ( Fig. 15 d ) vs. apical margin cleft of telson is more than half of its total length ( Fig. 10 e, f ); 2) palm of propodus of gnathopod II slightly oblique ( Fig. 12 g ) vs. palm of propodus of gnathopod II distinctly oblique ( Fig. 7 g ); 3) posterior margin of epimeral plate II is slightly oblique, almost straight ( Fig. 15 b ) vs. posterior margin of epimeral plate II is significantly oblique ( Fig. 10 b ).

For the differences from D. khalabensis Palatov et Marin sp.n. see below.

DISTRIBUTION AND ECOLOGY. The species is known only from the subterranean water flow in the Garakha Cave, southwestern Georgia, SW Caucasus [ Chertoprud et al., 2020 (as Synurella sp. ); present study]. This is the only cave-dwelling species in the genus Diasynurella .

Figures

Fig. 12. Diasynurella cavatica Palatov et Marin sp.n., Georgia, Samegrelo-Zemosvaneti, Chkhorotsqu district, Garakha Cave: 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. 12. Diasynurella cavatica Palatov et Marin sp.n., ГруЗиЯ, Самегрело – ВерхнЯЯ СванетиЯ, Чхороцкуский район, пеЩера Гараха: a — антенна I; b — вспомогательный 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. 13. Diasynurella cavatica Palatov et Marin sp.n., Georgia, Samegrelo-Zemosvaneti, Chkhorotsqu district, Garakha Cave: a — labrum (upper lip); b — labium (lower lip); c — lateralia; d — left mandible; e — same, incisor process and pars incisiva; f — right mandible; g — same, incisor process and pars incisiva; h — maxilla I; i — maxilla II; j — maxilliped. Рис. 13. Diasynurella cavatica Palatov et Marin sp.n., ГруЗиЯ, Самегрело – ВерхнЯЯ СванетиЯ, Чхороцкуский район, пеЩера Гараха: a — верхнЯЯ губа; b — нижнЯЯ губа; c — латералиЯ; d — леваЯ мандибула; e — то же самое, реЗцовый отросток и pars incisiva; f — праваЯ мандибула; g — то же самое, реЗцовый отросток и pars incisiva; h — максилла I; i — максилла II; j — максиллипеда.

Fig. 14. Diasynurella cavatica Palatov et Marin sp.n., Georgia, Samegrelo-Zemosvaneti, Chkhorotsqu district, Garakha 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. Рис. 14. Diasynurella cavatica Palatov et Marin sp.n., ГруЗиЯ, Самегрело – ВерхнЯЯ СванетиЯ, Чхороцкуский район, пеЩера Гараха: a — переопода III; b — дактилус PIII; c — переопода IV; d — дактилус PIV; e — переопода V; f — дактилус PV; g — переопод VI; h — дактилус PVI; i — переопода VII; j — дактилус PVII.

Fig. 15. Diasynurella cavatica Palatov et Marin sp.n., Georgia, Samegrelo-Zemosvaneti, Chkhorotsqu district, Garakha Cave: 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. 15. Diasynurella cavatica Palatov et Marin sp.n., ГруЗиЯ, Самегрело – ВерхнЯЯ СванетиЯ, Чхороцкуский район, пеЩера Гараха: a — ЭпимеральнаЯ пластина I; b — ЭпимеральнаЯ пластина II; c — ЭпимеральнаЯ пластина III; d — тельсон; e — плеопода III; f — крючки ретинакулы плеоподы II; g — уропода I; h — уропода II; i — уропода III.

Fig. 20. Diasynurella cavatica Palatov et Marin sp.n. (a, b) and D. khalabensis Palatov et Marin sp.n. (c–h): a, c — urosomal segments, lateral view; b, d — head; e — chela of gnathopod I; f — distoventral margin of chela of gnathopod I; g — chela of gnathopod II; h — distoventral margin of chela of gnathopod II. Рис. 20. Diasynurella cavatica Palatov et Marin sp.n. (a, b) и D. khalabensis Palatov et Marin sp.n. (c–h): a, c — уросомальные сегменты, вид сбоку; b, d — голова; e — клеШнЯ гнатоподы I; f — дистовентральный край клеШни GnI; g — клеШнЯ гнатоподы II; h — дистовентральный край клеШни GnII.

Fig. 8. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: 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. 8. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: a — верхнЯЯгуба; 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. 10. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: a — epimeral plate I; b — epimeral plate II; c — epimeral plate III; d — urosomal segments, lateral view; e, f — telson; g — pleopod III; h — hooks of retinacula of pleopod II; i — uropod I; j — uropod II; k — uropod III. Рис. 10. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: a — ЭпимеральнаЯ пластинка I; b — ЭпимеральнаЯ пластинка II; c — ЭпимеральнаЯ пластинка III; d — уросомальные сегменты, вид сбоку; e, f — тельсон; g — плеопода III; h — крючки ретинакулы плеоподы II; i — уропода I; j — уропода II; k — уропода III.

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).

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. 7. Diasynurella dzhamirzoevi Palatov et Marin sp.n., Russia, Dagestan, Magaramkent district, Samur forest: 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. 7. Diasynurella dzhamirzoevi Palatov et Marin sp.n., РоссиЯ, Дагестан, Магарамкентский район, Самурский лес: а — антенна I; b — вспомогательный жгутик антенны I; c — антенна II; d — гнатопода I; е — дистовентральный край клеШни GnI; f — гнатопода II; g — дистовентральный край клеШни GnII.