Habrobathynella krishna, Reddy, Yenumula Ranga & Totakura, Venkateswara Rao, 2010

Reddy, Yenumula Ranga & Totakura, Venkateswara Rao, 2010, A taxonomic revision of the genus Habrobathynella Schminke, 1973, with the description of four new species from southeastern India (Crustacea, Malacostraca, Bathynellacea), Zootaxa 2532, pp. 1-54 : 4-8

Habrobathynella krishna n. sp.

( Figs 2–8)

Type material. Holotype Ƥ (dissected on 3 slides) (C5837/2, C5838/2, C5839/2), allotype 3 (dissected on 3 slides) [MNHN-Sy20(1–3)] and 6 paratypes: 2 Ƥ (dissected on 3 slides each [MNHN-Sy21(1-3), MNHN- Sy22 (1-3)]; 1 Ƥ whole-mounted (MNHN-Sy25); 1 Ƥ in alcohol (MNHN-Sy42); 2 33 (dissected on 3 slides each) [MNHN-Sy23(1–3), MNHN-Sy24(1–3)]; also, 1 adult 3, 1 adult Ƥ and 2 juveniles (33) (in junior author’s collection), River Krishna at Ramannapeta village (16°45ʹ32ʹ N 80°07ʹ35ʹ E; elevation 39 m; water temperature 28°C; pH 7.5) in Guntur District, Andhra Pradesh, India, leg. V.R. Totakura, 27 July 2008.

Other material examined. 1 3 and 2 Ƥ in alcohol in 1 vial (MNHN-Sy43), River Krishna at Madipadu village (16°48ʹ50ʹ N 80°04ʹ22ʹ E, elevation 40 m) in Guntur District Andhra Pradesh, India, leg. V.R. Totakura, 12 October 2008.

Diagnosis. Male thoracopod VIII subglobular, with dentate and inner lobes moderately produced; outer lobe denticulate apically; exopod large, hook-like; basipodal seta occurring on a short prominence, very close to endopodal seta. Maxilla with 2 setae on small protuberance at inner distal corner of segment 1 and a fairly long claw-like seta on segment 2. Uropodal sympod with a row of 6–8 inhomonomous spines; penultimate spine longest and thickest whereas ultimate spine similar to proximal spines. Pleotelson and uropodal endopod with much reduced setae.

Description of adult female. Total body length of holotype 1.03 mm; paratypes 1.06–1.30 mm, mean 1.2 mm (n = 4). Body ( Fig. 2) elongate, heavily chitinised and perforated, thoracic and abdominal segments telescoping into each other to varying degrees, 9.2 times as long as wide. In lateral view, abdominal segments wider than thoracic segments. Head 1.3 times as long as wide, 11.5% longer than first 3 thoracic segments combined.

Antennule ( Fig. 3 a): 6-segmented, 27.5% longer than head, no sexual dimorphism. First segment with 1 plumose seta on small protuberance at outer subdistal margin, 1 dorsal plumose seta at outer distal corner, 2 short plumose setae and 1 long simple seta on dorsal surface. Second segment with 4 plumose setae on dorsal surface, 1 ventral seta at outer distal corner and 1 dorsal seta at inner distal corner. Third segment with 1 plumose and 1 simple setae at outer distal corner and 1 ventral seta at inner distal corner. Inner flagellum on third segment elliptical, bearing 2 apical and 1 subapical setae. Fourth segment with 1 plumose and 1 stub setae on distal margin; apophysis overreaching midlength of next segment and with 2 unequal plumose setae. Fifth segment with 3 equal aesthetascs, overreaching sixth segment, 1 seta at outer distal corner and 2 ventral setae at inner distal corner. Sixth segment with 3 aesthetascs and 4 unequal setae.

Antenna ( Fig. 3 b): 2-segmented, proximal segment bare, 0.4 times as long as distal segment; second segment 2.8 times as long as wide, with 1 tiny outer proximal seta, 2 unequal terminal setae, of which inner seta plumose and as long as segment, and 1 subterminal dorsal seta.

Labrum ( Fig. 3 c): dentate margin moderately vaulted on either side, bearing 10 main nearly uniform, pointed, curved teeth and 1 small tooth on either side. Also, 2 rows of fine spinules (ctenidia) and 3 teats on ventral surface, as illustrated.

Mandible ( Fig. 3 d–e): distal part of pars incisiva with 4 unequal teeth. Tooth of ventral edge large, with finely denticulate lateral margin. Pars molaris developed into subpyriform outgrowth, 1.2 times as long as wide, carrying 2 finely denticulate, curved lateral teeth and 3 straight slender, apparently smooth teeth in a group at distal end; also, 1 unarticulate, small tooth at distal outer corner with finely denticulate margins; very fine denticles occurring between inner teeth of pars molaris. Palp completely absent.

Paragnath ( Fig. 3 f): hemispherical lobe with teat-like projection at the middle; fine spinules on proximal margin, as illustrated.

Maxillule ( Fig. 3 g): with 2 endites; proximal endite small, oval, carrying 4 unequal claw-like pinnate spines on inner distal margin. Distal endite subcylindrical, 3.2 times as long as wide, and armed with 4 terminal claws, distalmost one large, bent inwards, 2 unequal claws on inner margin and 3 subterminal setae on outer distal margin.

Maxilla ( Fig. 3 h): 3-segmented, somewhat bent inwards; basal segment 1.8 times as long as wide, with 2 unequal slender setae, lying apart from each other on small protuberance at inner distal corner. Second segment 1.2 times as long as basal segment and armed with 13 setae including 2 setae at midlength of inner margin and 1 fairly long claw-like seta at inner distal corner. Third segment almost completely fused with terminal falcate claw, which has finely serrulate inner margin.

Thoracopods I–VII ( Figs 4 a–e, 5a–b): Th. I–VII gradually increasing in size; biarticulate, club-shaped epipod on Th. II–VII, exceeding midlength of basis. On all thoracopods, coxa with distinct conical projection at distal inner corner and basis with 1 simple slender seta, shorter than first endopodal segment. Exopod 2- segmented, about 0.8 times as long as endopod, first segment with 1 dorsal and 1 ventral plumose setae of unequal length. Second segment with 1 subterminal dorsal plumose seta and 1 terminal ventral barbed seta. Endopod 4-segmented, fourth segment smallest. Th. I with 2 ctenidia (1 dorsal, 1 ventral) near posterior end of second exopodal segment; endopod without ctenidia. Th. II–VII with 2 ctenidia (1 dorsal, 1 ventral) each near posterior end of first and second exopodal segments and also second and third endopodal segments, as illustrated. Setal formulae: Th. I: 1+0/0+1/0+1/2(0), Th. II–VII: 0+0/0+1/0+1/1(0).

Thoracopod VIII ( Fig. 5 c): small, somewhat triangular, plate-like lobe.

Pleopod 1: absent.

Uropod ( Fig. 7 a): sympod narrow medially, 4 times as long as maximum width, bearing 6 inhomonomous row of serrulate spines, proximal 4 spines almost equal in size; penultimate spine largest; ultimate spine small like proximal spines. Exopod straight, 34% of sympod length and armed with 1apical and 1 subapical unequal plumose setae. Endopod falcate, 66% of sympod length, distal inner margin ornamented with spinules and with 2 equal, much reduced plumose setae at proximal fourth of outer margin.

Pleotelson ( Figs 7 a–b): with 1 greatly reduced seta on either side at base of caudal furca.

Anal operculum: rounded in lateral view ( Fig. 7 a, b), medially concave in dorsal view ( Fig. 7 d).

Caudal furca ( Fig. 7 a–b): longer than maximum width, bearing 1 terminal and 3 inner spines with serrulate margins and 2 unequal dorsal setae; each spine with transverse row of delicate spinules at base; furcal organ small, ventral.

Description of adult male. Total body length of allotype 1.29 mm, paratypes 0.9–1.4 mm, mean 1.3 mm (n = 4). Body and all appendages except Th. VIII as in female.

Thoracopod VIII ( Figs 5 f–g, 6a–d): subglobular in lateral view, protopod of moderate size. Outer lobe much wider than long, apically denticulate, fused with protopod, extending but a little beyond base of basipod. Both dentate and inner lobes moderately produced, overreaching exopod. Dentate lobe only slightly longer than inner lobe and with a row of about 6 denticles. Inner lobe somewhat rectangular in latero-external and –internal views. Basipod well defined at base and armed with 1 seta arising from a short prominence at outer distal corner and 2 unequal spinules at inner distal corner. Exopod relatively large, hook-like and with about 6 fine apical teeth (clearly visible in ventral view), generally closely pressed against dentate lobe. Endopod greatly reduced, being represented by a seta, inserted very close to basipodal seta.

Variation. In adults, the uropodal exopod is incurved and uropodal endopod with proximal indentation on inner margin ( Fig. 7 b). Number of spines borne by the uropodal sympod varies between 6 and 8 ( Fig. 7 a–c). The female Th. VIII varies somewhat in size and shape in paratypes ( Fig. 5 d–e).

Description of juvenile ( Fig. 8 a–c): Total length 0.82 mm and 0.88 mm. Body form as in adult, 8 times longer than maximum width. Abdominal segments wider than thoracic segments. Head 1.2 times as long as wide. Body segmentation and various details of cephalic appendages and caudal furca as in adult, but differing in the following respects: Th. I–VI adult-like; Th. VII ( Fig. 8 a) rudimentary; epipod present; basis without seta; exo- and endopod unsegmented; exopod slightly shorter than endopod and with 2 terminal weak setae; endopod unarmed. Th. VIII ( Fig. 8 b) rudimentary; protopod large and outer lobe wide and undifferentiated. Basipodal and endopodal setae absent. Basipod with only 1 spinule at inner distal corner. Dentate lobe ending in triangular projection. Pleotelson as in adult but setae absent. Uropodal exopod straight, 35.4% of sympod length and endopod 63% of sympod length; armature as in adult.

Etymology. The specific epithet alluding to the River Krishna , the type locality of the new species, is proposed here as a noun in apposition to the generic name.

Figures

FIGURE 3. Habrobathynella krishna n. sp., holotype female (a) antennule, dorsal; (b) antenna, dorsal; (c) labrum, ventral; (d) mandible, lateral; (e) same, latero-ventral; (f) paragnath, ventral; (g) maxillule, ventral; (h) maxilla, dorsal.

FIGURE 4. Habrobathynella krishna n. sp., holotype female. (a – e) Th. I – V.

FIGURE 5. Habrobathynella krishna n. sp., holotype female (a – c), allotype male (f), paratype female (d – e), and paratype male (g). (a – b) Th. VI – VII; (c – e) Th. VIII, lateral; (f) Th. VIII, latero-external; (g) Th. VIII, latero-internal.

FIGURE 7. Habrobathynella krishna n. sp., holotype female (a), allotype male (b) and paratype female (c – d). (a) pleotelson, lateral; (b) same, dorso-lateral; (c) uropod, lateral; (d) anal operculum, dorsal.

FIGURE 8. Habrobathynella krishna n. sp., male juvenile. (a) Th. VII; (b) Th. VIII, latero-external; (c) pleotelson, lateral.