Oziotelphusa ravi Raj & Kumar & Ng 2017, new species
Creators: name: Raj, Smrithy
name: Kumar, Appukuttannair Biju
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Gecarcinucidae
Oziotelphusa
Oziotelphusa ravi

description: Oziotelphusa ravi, new species
(Figs. 1–5, 6A, 7A, B, 8A, B, 9A, B)
Material examined. Holotype: male (41.5 × 30.4 mm) (ZSI), in ditches and rice field near Nagercoil, Kanyakumari district, Tamil Nadu, 8°18’51.792”N, 77°25’20.111”E, coll. R. Ravineesh & R. S. Albert, 22 March 2017. Paratypes: 1 male (45.4 × 33.5 mm), 2 females (45.0 × 34.0 mm, 44.5 × 32.8 mm) (ZRC 2017.158), 2 females (54.3 × 42.8 mm, 49.6 × 35.7 mm) (DABFUK), same data as holotype.
Comparative material. Oziotelphusa biloba Bahir & Yeo, 2005: holotype male (41.8 × 29.8 mm) (ZRC 2003.0246), Kodagara Village on Trissur-Chalakudy road, Kerala, India, 10°21’30.7"N, 076°08’45.0"E, 6 m, coll. 2005. Oziotelphusa kerala Bahir & Yeo, 2005: holotype male (38.3 × 27.8 mm) (ZRC 2003.0244), Kolaththuppuzha-Tenmalai Road, Kerala, India, 08°54’12.7”N, 077°32’7.2”E, 120 m, coll. 2005.
Diagnosis. Carapace dorsal surface strongly convex (Figs. 1A, 2E, F, 3A, B, 5A, 6A); cristate margins of median tooth of posterior margin of epistome fused distally, forming distinct bilobed tip in anterior view, more prominent in males (Fig. 3C, 7A, 8A, B); frontal margin straight in dorsal view; epibranchial tooth small, above lateral edge of postorbital crista, level with supraorbital margin (Figs. 1A, 2E, F, 3A, B, 5A, 6A); postorbital region moderately narrow, concave (Figs. 1A, 3A, B, 5A, 6A, 7A); postorbital cristae entire, sharp, gently sinuous (Figs. 3B); branchial region highly inflated (Figs. 1A, 3A, B, 5A, 6A, 7A); frontal median triangle as broad as frontal margin, dorsal margin not fused with lateral margins (Figs. 3C, 7A). Suture between anterior thoracic sternites 2 and 3 visible as a deep, narrow groove barely reaching lateral margins; suture between sternites 3 and 4 distinct as a moderately broad, deep groove reaching lateral borders as barely discernible depression (Figs. 3D, 7B). Male pleon broadly triangular, somite 6 narrowly trapezoidal, slightly wider than long with concave lateral margins (Fig. 3D, E). G1 terminal segment ca. 0.3 × length of subterminal segment, sharply bent outwards at angle of about 45° (along longitudinal axis), conical, tapering gradually to truncate tip, proximal part of outer margin of subterminal segment with prominent deep concavity (Figs. 3G, 4A–E). G2 ca. 1.2 times length of G1, distal segment ca. 0.5 × length of basal segment (Fig. 4F, G).
Description of male. Carapace broader than long; dorsal surface strongly convex (Figs. 1A, 2E, F, 3A, B, 6A, 7A; frontal margin straight in dorsal view, frontal median triangle as broad as frontal margin, dorsal margin not fused with lateral margins (Figs. 1A, 2E, F, 3A–C, 6A, 7A); suborbital regions rugose, glabrous; pterygostomial region smooth, glabrous (Fig. 3C, 7A); epigastric cristae distinct, slightly anterior of postorbital cristae; epigastric groove Y-shaped (Fig. 3B); cervical groove deep, narrow; H-shaped groove distinct; external orbital tooth prominent, broadly triangular, tip almost in line with frontal margin, clearly demarcated from epibranchial teeth by a V-shaped notch, outer margin concave, inner margin gently curved, joins supraorbital margin; epibranchial tooth distinct, small, blunt, above lateral edge of postorbital crista, level with supraorbital margin; anterolateral margin strongly convex, smooth (Figs. 1A, 2E, F, 3A, B, 6A). Subhepatic region rugose (Fig. 3C, 7A). Postorbital region moderately narrow, concave; postorbital cristae entire, sharp, gently sinuous; anterior part of branchial regions distinctly inflated (Fig. 7B). Posterolateral margin gently concave, joins straight posterior carapace margin (Figs. 1A, 2E, F, 3A, B, 6A); orbits relatively rounded, infra- and supraorbital margins with short setae; eyes filling up most of orbital space; eye stalk moderately long, stout; cornea moderately large, pigmented (Figs. 3C, 7A). Supraorbital margin gently concave at edges (Figs. 3C, 7A). Suborbital margin concave, complete, lined with very low, rounded granules (Figs. 3C, 7A). Antennae long, reaching cornea of eyes; antennules long folded in narrow fossae (Figs. 3C, 7A). Posterior margin of epistome with median tooth, lateral cristate margins of tooth fused at tip to form distinct bilobed structure with distinct median notch when viewed frontally, bifurcation extending towards posterior surface of tooth as 2 cristae (Figs. 3C, 7A, 8A, B).
Third maxillipeds covering most of buccal cavity when closed; ischium subrectangular, surface pitted, with distinct submedian oblique groove; merus subovate; exopod relatively slender, reaching lower third of merus, with distinct long flagellum reaching almost entire width of merus (Fig. 3F).
Chelipeds asymmetrical (Figs. 1, 3A, H, I, 6A); dorsal, ventral and lateral margins of merus lined with low granules, appears weakly serrated. Outer surface of carpus rugose; inner distal angle with prominent sharp tooth (Figs. 1A, 3A, 6A). Major chela stouter than minor chela (Fig. 3I); cutting edges of both fingers with variously sized teeth, median tooth largest; fingers of minor chela similar to that of major chela but palm more slender, other teeth on cutting edges relatively smaller (Fig. 3H).
Ambulatory legs slender; second pair longest, last pair shortest (Figs. 3A, 6A). Outer surface of merus slightly rugose, dorsal margin weakly serrated to entire without obvious subdistal spine; outer surface of carpus with submedian cristae on first to third legs, that on fourth leg almost smooth; lateral margins of dactylus with short, sharp chitinous spines (Figs. 3A, 6A).
Suture between thoracic sternites 2 and 3 distinct, barely reaching lateral margins; suture between thoracic sternites 3 and 4 deep, lateral parts very shallow, barely discernible (Figs. 3D, G, 7B). Sutures between sternites 4/ 5, 5/6, 6/7 medially interrupted; suture between sternites 7/8 complete (Fig. 3D). Pleonal locking mechanism with prominent but low, anteriorly directed tubercle on submedian part of sternite 5 (Fig. 3D).
Sternopleonal cavity deep, reaching imaginary line connecting submedian part of coxae of chelipeds (Figs. 3D, 7A). Pleon broadly T-shaped; somites 1, 2 broadly rectangular, reaching to bases of coxae of last ambulatory legs; somites 3–5 trapezoidal, lateral margins of somites 3–5 strongly convex, convex and gently concave, respectively; somite 6 narrowly trapezoidal, proximal part of outer margin wider than distal margin, lateral margins concave (Figs. 3D, E, 7A).
G1 with terminal and subterminal segments clearly demarcated by distinct membranous suture; terminal segment ca. 0.3 times length of subterminal segment, sharply bent outwards at angle of about 45° (along longitudinal axis), conical, tapering gradually to truncate tip, distal surface with numerous very small squamiform spines; subterminal segment moderately stout, broad basally, gently tapering distally, proximal part of outer margin with prominent deep concavity (Figs. 3G, 4A–E). G2 ca. 1.2 × length of G1, with long distal segment, ca. 0.5 × length of basal segment (Fig. 4F, G).
Females. The largest paratype female specimen (54.3 × 42.8 mm, DABFUK) resembles the holotype in most non-sexual characters. Its pleon is ovate, covering all the surfaces of the thoracic sternites (Fig. 5B). The vulvae on somite 6 are moderately large, ovate and positioned near the posterior margin of sternite 5 (Fig. 5C).
Variation. The form of the median tooth on the posterior margin of the epistome varies slightly between sexes. In males, the cristate lateral margins fused at the tip to form a distinct bilobed structure with a clear median notch when viewed frontally (Fig. 8A), but in female specimens, the notch is relatively less distinct.
Colour in life. In males, the dorsal carapace surface is brown with distinct patches of pale orange on the various regions; chelipeds and ambulatory legs light brown with ventral surfaces yellowish-white to white (Fig. 1). Females generally have a similar colour and pattern (Fig. 2C, E) although in one specimen (49.6 × 35.7 mm, DABFUK) the orange patches are almost undiscernible with the carapace appearing a more uniform pale brown (Fig. 2F).
Distribution. The species is known only from type locality Keeriparai, near Nagercoil, in Tamil Nadu state, southern India (Fig. 10).
Etymology. The species is named after our colleague R. Ravineesh who told us about the rice field crabs in his home village and arranged for family members to help collect material. The name is used as a noun in apposition.
Remarks. Oziotelphusa ravi, new species, most closely resembles O. kerala and O. biloba in carapace morphology but can easily be distinguished by its male pleonal and G1 characters. The G1 terminal segment of O. ravi, new species, is relatively stout, cylindrical, gently tapered distally and is distinctly bent laterally outwards at an angle of about 45° along the longitudinal axis, like in O. kerala (Fig. 9F). In O. kerala, however, the G1 terminal segment is relatively longer (Fig. 9F; Bahir & Yeo 2005: fig. 39B–D); and the G1 subterminal segment is broad with the proximal part of the outer margin gently concave (Fig. 9F; Bahir & Yeo 2005: fig. 39 B, C), while in O. ravi, new species, the terminal segment is relatively shorter and the subterminal segment is proportionately broader and the proximal part of the outer margin is deeply concave (Figs. 5A, B, 9B). In addition, the male pleonal somite 6 of O. kerala is also proportionately longitudinally more slender than that of O. ravi, new species (Fig. 9E versus Figs. 3E, 9A). The form of the median tooth of the posterior epistomal margin is superficially similar in these two species but in O. kerala, the cristate lateral margins fuse seamlessly at the tip, not forming an bifurcated structure in frontal view, although the inner surface of the tooth does bifurcate (Fig. 8E, F). In O ravi, new species, the tip of the median tooth is distinctly bilobed even in frontal view (Fig. 8A, B).
The structure of the median tooth of the posterior epistomal margin in O. biloba and O. ravi, new species, are similar (Fig. 8A–D), but the male pleonal somite 6 of O. biloba is proportionately very slender longitudinally, with the lateral margins prominently concave (Fig. 9C) whereas in O. ravi, new species, it is proportionately broader with less concave margins (Fig. 9A). The G1 structures of O. biloba and O. ravi, new species, are quite different, even though both possess a prominent concavity on the proximal part of the outer margin (Fig. 9B, D). In O. biloba, the G1 terminal segment is more sharply tapering and is prominently bent outwards at almost 90° (Fig. 9D; Bahir & Yeo 2005: fig. 30 C–H) (G1 terminal segment stouter and bent at only about 45° along the longitudinal axis in O. ravi, new species; Fig. 9B).
Oziotelphusa aurantia (Herbst, 1799) and O. bouvieri (Rathbun, 1904) are the other species found in the state of Tamil Nadu and superficially resemble O. ravi, new species, in general carapace features; and both occur in the southeastern part of the state (Bahir & Yeo 2005). Oziotelphusa aurantia can easily be separated from O ravi, new species, in having the tip of the median triangle of the posterior epistomal margin not bilobed (Bahir & Yeo 2005: fig. 9B) (versus tip distinctly bilobed; Fig. 8A); the male pleonal somite 6 is more trapezoidal in shape with barely concave lateral margins (Bahir & Yeo 2005: fig. 9A) (versus male pleonal somite 6 narrowly trapezoidal with lateral margins concave; Figs. 3E, 7B); and the G1 subterminal segment is proportionately much stouter with a smaller concavity on the proximal part of the outer margin with the terminal segment less distinctly bent (Bahir & Yeo 2005: fig. 9C–E, 10A, B) (versus G1 subterminal segment more slender, the proximal part of the outer margin has a prominent deep concavity and the terminal segment is strongly bent 45° along the longitudinal axis; Figs. 4A–E, 9B). Oziotelphusa bouvieri is easily distinguished from O. ravi, new species, in having the epibranchial tooth more prominent and sharper (Bahir & Yeo 2005: fig. 17A) (versus epibranchial tooth low; Figs. 3A, B, 6A); the tip of the median triangle of the posterior epistomal margin is not bilobed (Bahir & Yeo 2005: fig. 17B) (versus tip distinctly bilobed; Fig. 8A); the male pleonal somite 6 is proportionately broader (Bahir & Yeo 2005: fig. 17C) (versus male pleonal somite 6 narrowly trapezoidal with lateral margins concave; Figs. 3E, 7B); and the G1 subterminal proportionately stouter, the proximal part of the outer margin is sinuous without a deep concavity and the terminal segment is relatively shorter and less distinctly bent (Bahir & Yeo 2005: fig. 16A–E) (versus G1 subterminal segment more slender, the proximal part of the outer margin has a prominent deep concavity, and the terminal segment is strongly bent at 45° along the longitudinal axis; Figs. 4A–E, 9B).
Ecology. Oziotelphusa ravi, new species, lives in ditches and drainage channels in banana plantations, as well as ponds and rice fields in Tamil Nadu; where the water is slow flowing or stationary (Fig. 2A). The crabs dig relatively deep burrows just above the water level (Fig. 2B), coming out at night to forage on the vegetation in and around the water (Fig. 2C). Many of the adult females collected in the period of study were carrying juvenile crabs underneath their pleon (Fig. 2D).
The species faces no immediate threats to its survival as its closely associated with rice fields and other manmade aquatic habitats.
description: Published as part of Raj, Smrithy, Kumar, Appukuttannair Biju & Ng, Peter K. L., 2017, A new species of freshwater crab of the genus Oziotelphusa Müller, 1887 (Crustacea: Decapoda: Brachyura: Gecarcinucidae) from Tamil Nadu, southern India, pp. 225-236 in Zootaxa 4363 (2) on pages 226-234, DOI: 10.11646/zootaxa.4363.2.3, http://zenodo.org/record/1098698