Eobogidiella venkataramani, Sidorov, Dmitry A., Katz, Aron D., Taylor, Steven J. & Chertoprud, Mikhail V., 2016

Sidorov, Dmitry A., Katz, Aron D., Taylor, Steven J. & Chertoprud, Mikhail V., 2016, A reassessment of the phylogenetic utility of genus-level morphological characters in the family Bogidiellidae (Crustacea, Amphipoda), with description of a new species of Eobogidiella Karaman, 1981, ZooKeys 610, pp. 23-43 : 29-33

Taxon classification Animalia Amphipoda Bogidiellidae

Eobogidiella venkataramani sp. n. Figs 5, 6, 7

Diagnosis.

Habitus typical of a stygomorphic bogidiellid, combining a number of features found in other genera of this family.

Primary characters: maxilla 1 with vestigial, single-segmented, symmetrical palps; pleopods 1-3 with single-segmented, reduced inner rami.

Secondary characteristics: ventral surface of pereonites 2-7 bearing sternal humps; coxal gills on pereopods 3-6; antenna 1 with reduced, single-segmented, minute accessory flagellum; mandibles with tiny, vestigial molars with 2 short spines and 1 plumose seta; maxilliped lacking coxal endite; apparent sexual dimorphism (spines on uropods 1 and 2 modified).

Type locality.

Spring fed swamp in the upper reaches of a small logged brook (14.218667°N; 74.821667°E) in the Shirawati River basin, altitude above sea level 550 m, Western Ghats, Karnataka, India.

Type material.

Holotype specimen. INDIA: probable ♂, 6.5 mm, X43794/Cr-1621-FEFU, vicinity of Jog Falls, Karnataka state, collected 5 Dec. 2008 by M.V. Chertoprud. Deposited in the Zoological Museum of the Far East Federal University, Vladivostok (FEFU).

Accompanying fauna: Goerodes sp. ( Trichoptera : Lepidostomatidae ), Isca sp. ( Ephemeroptera : Leptophlebiidae ), Phanoperla sp. ( Plecoptera : Perlidae ), Macromyia sp. ( Odonata : Corduliidae ), and many terrestrial leeches ( Hirudinida) on the banks.

Etymology.

The specific epithet honors the former Director of Zoological Survey of India, Dr. K. Venkataraman, whose assistance was pivotal in the early stages of this research.

Description of holotype

X43794/Cr-1621-FEFU. General body morphology (Figs 5A, C, 6A, 7J). Body unpigmented, smooth, sparsely setose with fine setae. Head longer than deep and longer than first pereon segment; rostrum pointed, interantennal lobe distinct, evenly rounded apically; eyes absent. Epimeral plates 1-3 with acute posterodistal corners and with thin setae on posterior margin, ventral margin of plates unarmed. Telson subquadrate with apical margin roundly convex, width: length ratio 1: 0.75, bearing 4 long notched spines subapically. ANTENNAE (Figs 5A, 6A). Antenna 1 about 38% of body length; flagellum with 17 articles, each article with 2-4 short setae, aesthetascs present on 12 distal flagellar articles; peduncular article ratio 1: 0.67: 0.3; proximal article of peduncle with 3 notched spines on ventral margin; accessory flagellum small, comprised of one article. Ratio of lengths of antenna 1: antenna 2, 1: 0.75; flagellum of antenna 2 with 5 articles, each article sparsely setose; peduncle article 4 as long as article 5; flagellum shorter than peduncle (articles 4+5); last two peduncular articles with notched spines and long, stiff setae; gland cone not markedly elongate. MOUTH PARTS (Fig. 6 A–I). Labrum subtrapezoidal, long as broad, clypeus unfused. Inner lobes of labium well developed, outer lobes broad, densely setose laterally, with thin setae marginally, and lightly setose with shorter setae mediodistally, mandibular process narrow. Left mandible: incisor with 4 teeth, lacinia mobilis consisting of 2 finely denticulate plates of similar size; row of 3 densely plumose spines between lacinia and molar; molar vestigial, conical, bearing 2 short spines and 1 plumose seta. Right mandible: incisor with 4 teeth, lacinia mobilis with 5 teeth, row of 2 densely plumose spines between lacinia and molar; molar similar to that of left mandible. Mandibular palp article 2 slightly longer and broader than article 3; proximal palp article without a seta; the second article with 2 long setae on inner margin; distal article narrow, with 3 long setae unequal in length on apex, and numerous small, fine setae near lateral margin on distal half of article. Maxilla 1 palp reduced, single-segmented, with 2 long setae of equal length on apex (palps symmetrical); outer plate with 7 simple spines, 3 of which are finely pectinate; inner plate broadly rounded distally, with 2 plumose setae. Maxilla 2 plates similar in size, inner plate with 6 apical setae of varying size, outer plate with 5 long, finely pectinate setae and 3 short setae apically. Maxilliped with inner and outer plates short; outer plate with 2 apical spines accompanied by 2 stiff setae on lateral face; inner plate broad, with 1 bifid apical spine and 3 stiff naked subapical setae, 2 setae located medially on small pedestal; palp four-segmented; palp article 2 longest, nearly straight on outer margin, shallowly convex on inner margin, with a row of 8 long, simple setae along inner margin; article 3 half as long as article 2, with sharply pointed, pubescent cuticular projection distally and bearing 2 sets of long setae apically; article 4 about as long as preceding article, curved and tapering distally, with dorsal seta, and bearing 2 longer setae at base of nail, nail 0.33 × length of pedestal. Lateralia with 14 strong, pectinate spines and 1 short simple spine. COXAL PLATES, GILLS AND STERNAL RESPIRATORY STRUCTURES (Fig. 5A, B). Coxal plates 1-7 wider than long, free, not overlapping with one another, coxa 4 largest; coxal plates 5-7 progressively smaller towards the posterior, semicircular, acuminate posteriorly and bearing 1 stiff seta posteriorly. Coxal gills oblong, stalked on coxae 3 to 6. Ventral surface of pereonites 2-7 bearing sternal humps. GNATHOPODS 1 AND 2 (Fig. 5D, E). Gnathopod 1, basis short, broadest medially, with 2 short setae on anterior margin; merus with 3 stiff setae on distoposterior margin, posterior surface densely spinose; carpus sub-triangular, with 2 setae of equal length on narrowly rounded spinose distoposterior lobe; propodus oblong, about 1.8 × longer than broad, palmar margin slightly convex, 3 × longer than posterior margin, palmar angle indistinct, with 1 group of oblique, long setae laterally on basal half of segment; anterior margin with 1 seta, and a group of 2 setae anterodistally; palm armed with 2 pairs of weakly notched spines accompanied by 10-12 stiff, tiny notched setae along inner and outer faces; dactylus falcate, about 70% length of propodus, demarcation of nail indistinct with 2 setules at hinge. Gnathopod 2, basis sublinear, with 3 short setae on distal one third of anterior margin; ischium posterior surface densely spinulose with one longer, posterodistal seta; merus with posterior surface densely spinulose, with two stiff longer, posterodistal seta; carpus triangular and slightly elongate, with numerous thin subequal setae on broadened, spinulose ventral lobe, 1 long seta distally on medial face; propodus small, slightly shorter than propodus of gnathopod 1; palmar margin oblique, subequal in length to posterior margin, palmar angle poorly developed and broadly rounded, with 1 group of oblique long setae subdistally; anterior margin with 2 setae, anterodistal group with 3 setae; palm armed with 1 pair of weakly notched spines accompanied with 5-6 stiff, tiny, notched setae along inner and outer faces; dactylus similar to that of gnathopod 1. PEREOPODS 3, 4, 6 (pereopods 5 and 7 missing) (Fig. 7 A–C); lacking lenticular organs. Pereopods 3-4 subequal, bases rather long and narrow, each with 1 stiff seta on anterodistal margin; dactyli about 0.33 × length of corresponding propodi. Pereopod 6 length 0.35 × body length; basis narrowed distally, length:width is 1:0.4; posterior margin with 3 notched spines and 4 setae; anteriorly 4 notched spines and 2 setae; carpus short, length 0.5 × preceding article, armed with strong spines on lateral and distal margins; dactylus about 0.25 × length of corresponding propodus. PLEOPODS AND UROPODS (Fig. 7 D–I). Pleopods 1-3 subequal; peduncular articles linear, in ratio 1:1:0.7, with 2 retinacula each; inner ramus reduced, 1-segemented, length less than basal width of first segment of outer ramus; outer ramus 3-segmented, fringed with long, plumose setae at distal end of each segment. Uropod 1 peduncle without basofacial spine; with 3 dorsolateral spines and distally with 1 very strong dorsomedial spine; exopodite:endopodite length 1:0.88; endopodite length 0.5 × peduncle; rami straight, each armed with 4 strong spines apically, 1 of them much larger and with marginal serrations. Uropod 2 peduncle with 1 dorsolateral spine and 1 strong dorsomedial spine distally; exopodite:endopodite length 0.86:1; endopodite length 0.7 × peduncle; rami straight, each armed with 4 spines apically, 1 of them much larger and another modified (Fig. 7H). Uropod 3 long, with peduncle about 1 half the length of rami, armed with two notched spines on apex; endopodite curved in basal half, with 8 singly inserted notched spines along margins and 4 apical spines; exopodite straight, slightly tapering in distal half, with 6 singly inserted notched spines along margins and 5 apical spines.

Variability.

Unknown.

Sexual dimorphism.

Unknown, but modified spines on uropods 1 and 2 probably represent a male-specific trait.

Distribution and ecology.

Eobogidiella venkataramani sp. n. dwells in a spring-fed brook habitat located on the flat bottom of a small valley in the rainforest. The biotope is a small trickling swampy stream 1-3 m wide and 0-0.05 m deep, without flow, water temperature +22 °C, and a substrate comprised of wet litter, detritus, stones, clay. Known only from type locality.

Taxonomic comments.

Eobogidiella venkataramani sp. n. is distinguished from Eobogidiella purmamarcensis by the following characteristics (characteristics of the latter in parentheses): antenna 2 reaching 75% of antenna 1 length (about 50%); accessory flagellum comprised of 1 article (2 articles); molar vestigial, non-triturative (developed, triturative); mandibular palp article 3 with 3 setae on apex (1 seta); maxilla 1 inner plate with 2 setae (3 setae); maxilla 2 plates broad (narrow); maxilliped palp article 2 narrow (very broad); lenticular organs absent (present); telson with apical margin convex (with excavation apically).