Habrobathynella parakrishna, Totakura, Venkateswara Rao & Reddy, Yenumula Ranga, 2014

Totakura, Venkateswara Rao & Reddy, Yenumula Ranga, 2014, Three new species of the genus Habrobathynella Schminke, 1973 (Syncarida, Parabathynellidae) from the peninsular India, Zootaxa 3826 (1), pp. 139-168 : 149-157

Habrobathynella parakrishna n. sp.

( Figs 9–15 )

Type locality. Farm bore (water temperature 28°C; pH 7.0) in the riparian zone of the River Krishna (only 8 m from the river channel) at Mopidevi village, 30 km from the coastal ancient port town of Machilipatnam (16.17°N, 81.13°E; elevation 6 m) in Krishna District, Andhra Pradesh, South India ( Fig. 1 ).

Type material examined. Holotype ♂ (MNHN-IU-2013-11839), dissected on 4 slides and allotype ♀, dissected on 3 slides (MNHN-IU-2013-11840); and 5 paratypes: 1 ♂, dissected on 4 slides (MNHN-IU-2013- 11841); 1 ♂ whole-mounted on 1 slide (MNHN-IU-2013-11842), 2 ♂♂ and 1 ♀ (MNHN-IU-2013-11843), preserved in alcohol in 1 vial. 18 April 2008, Coll. V. R. Totakura.

Diagnosis. Male Th VIII somewhat rectangular in lateral, anterior and posterior views; dentate and inner lobes moderately produced; outer lobe smooth, fused with protopod; exopod plate-like, ending in 3 dentate structures. Th I with inner seta on first endopodal segment. Antennular sixth segment with 3 unequal aesthetascs subapically. Maxilla with 1 seta on small, protuberant inner distal corner of proximal segment; distal segment with 1 claw-like seta which is 51% as long as apical claw, and 1 nearly similar seta at outer distal angle. Uropodal sympod with inhomonomous row of 5 spines; penultimate spine longest and thickest; ultimate spine as long as proximal ones; uropodal endopod with shorter setae than endopodal spur. Pleotelson broadly rounded in lateral view. Labrum only slightly vaulted on either side, with 8 main large, straight teeth besides 8 tiny ones on either side.

Description of adult male. Total body length 1.09 mm; paratypes 0.91–1.09 mm. Body ( Fig. 9 ) elongate, heavily chitinised and perforated; 8.6 times as long as wide; thoracomeres and pleomeres telescoping into each other to varying degrees. In lateral view, pleomeres wider than thoracomeres. Head ( Fig. 9 ) about as long as wide, 1.2 times as long as first 2 thoracomeres combined.

Antennule ( Figs 9 , 10 a): 6-segmented; no sexual dimorphism, and measuring 21.1% longer than head. First segment with 1 plumose seta on small protuberance at about mid-outer margin, 1 plumose seta at outer distal corner, 1 plumose and 1 simple setae on dorsal surface subdistally, and 1 small plumose seta on inner margin subdistally. Second segment with 3 plumose setae in a row on dorsal surface, 2 ventral plumose setae near outer distal corner, 2 simple setae at inner distal corner. Third segment with 1 long, simple seta and 1 short plumose seta at outer distal corner, 1 ventral simple seta subdistally, and 1 plumose seta on distal margin. Inner flagellum subovate, bearing 3 unequal simple setae. Fourth segment with stout apophysis overreaching midlength of next segment and with 2 unequal plumose setae; 1 plumose seta on small protuberance and 1 stub seta on distal margin. Fifth segment with 3 unequal aesthetascs, overreaching sixth segment, 1 seta at outer distal corner and 2 simple setae and 1 small, modified seta at inner distal corner. Sixth segment with 3 unequal, subapical aesthetascs and 4 unequal setae.

Antenna ( Fig. 10 b): 2-segmented, proximal segment bare, 0.6 times as long as distal segment; distal segment 2.3 times as long as wide, with 1 tiny outer proximal seta, 2 unequal terminal setae, of which inner seta plumose and 1.5 times as long as segment, and 1 subterminal dorsal seta.

Labrum ( Fig. 10 c): dentate margin only slightly vaulted on either side, bearing 8 main nearly uniform, pointed, curved teeth (2 bicuspid) and 8 distinctly small teeth on either side. Also, 4 teats on ventral surface, as illustrated.

Mandible ( Fig. 10 d–e): distal part of pars incisiva with 4 unequal teeth. Tooth of ventral edge somewhat large, articulate, with smooth lateral margins. Pars molaris developed into subpyriform outgrowth, 0.8 times as long as wide, carrying 2 denticulate, curved lateral teeth and 3 straight slender teeth (distal one small) in a group at distal end. Palp completely absent.

Paragnaths ( Fig. 10 f): coupler rounded and short; lateral lobes also short, relatively broad; denticulate spinules (‘ctenidia’) present on coupler as well as lateral lobes.

Maxillule ( Fig. 11 a): with 2 endites; proximal endite small, oval, carrying 4 unequal claws on inner distal margin. Distal endite subcylindrical, 3.7 times as long as wide, and armed with 2 terminal claws, distal one large, 4 unequal claws on inner margin, proximalmost claw small, and 3 subterminal setae on outer distal corner.

Maxilla ( Fig. 11 b): 2-segmented, somewhat bent inwards; basal segment 1.7 times as long as wide, with 1 long slender seta lying on small subtriangular protuberance at inner distal corner. Second segment 1.7 times as long as basal segment and armed with 15 setae, of which 3 claw-like setae (2 at inner distal corner, 1 on outer apical margin) and 1 middle seta. Third segment completely fused with terminal falcate claw, which has finely serrulate distal inner margin.

Th I–VII ( Figs 12 a–d, 13a–c): Th I with 1 inner seta on first endopodal segment. Setal formula: 1+0/0+1/0+1/ 2(0). Th II–VII same as in H. ajraoi n. sp.

Th VIII ( Figs 14 a–e): rectangular in lateral views, triangular in ventral view; protopod of moderate size. Outer lobe conical, fused with protopod. Both dentate and inner lobes moderately produced, overreaching exopod. Dentate lobe only slightly longer than inner lobe and with 2 rows of fine denticles. Inner lobe somewhat conical in latero-external and latero–internal, anterior and posterior views ( Fig. 14 a–d), but rectangular in ventral view ( Fig. 14 e). Basipod well defined and armed with 1 seta at inner distal corner. Exopod plate-like with 3 large dentate projections. Endopod represented by 1 seta, inserted considerably away from basipodal seta.

Pleopod 1 absent.

Uropod ( Figs 15 a, b): sympod 3.9 times as long as maximum width, bearing inhomonomous row of 5 serrulate spines, proximal 3 spines and ultimate spine similar in size, penultimate spine thickest and largest. Exopod straight, 35.7% of sympod length and armed with 1 apical and 1 subapical unequal, barbed setae, subapical seta about half as long as apical one. Endopod falcate, 67% of sympod length, serrulate on inner distal margin and with 2 unequal small setae at proximal fourth of outer margin; outer seta slightly longer than inner one.

Pleotelson ( Fig. 15 a): broadly rounded at postero-lateral angle, with 1 small seta on either side at base of caudal furca; seta shorter than furca.

Anal operculum ( Fig. 15 d): medially concave in dorsal view.

Caudal furca ( Fig. 15 a): slightly longer than maximum width, bearing 1 terminal and 3 inner spines with serrulate margins and 2 unequal dorsal plumose setae; furcal organ small, ventral.

Description of adult female. Total body length 1.15 mm. Body and all appendages except Th VIII as in male.

Th VIII ( Fig. 11 c): small, broadly triangular, plate-like lobe.

Variation. Uropodal exopod incurved only in 1 paratype ( Fig. 15 c).

Etymology. The specific epithet alludes to the remarkable affinity of the new species with its Indian congener, H. krishna (Latin para = beside), and agrees in gender with the feminine generic name.

Ecology. H. parakrishna n. sp. is so far known only from the type locality.

Remarks. The new species has closest affinity with the Indian H. krishna in having an identical character state of the spine row on uropodal sympod where the penultimate spine is longest and thickest but all other spines are similar in size. Also, the setae on uropodal endopod are shorter than the endopodal spur; the penile lobes of the male Th VII are moderately developed, and the pleotelson is rounded in lateral view (see Ranga Reddy & Totakura 2010).

The new species can, however, be easily distinguished from H. krishna by the following characters: in the male Th VIII, the outer lobe smooth vs. denticulate; basipod without vs. with ornamentation; endopodal seta lying away from vs. close to basipodal seta; and exopod short vs. elongate. The female Th VIII is small vs. large. The dentate margin of labrum has eight, large vs. ten, small main teeth. The mandibular pars molaris subquadrate vs. subpyriform, with three large vs. four small distal teeth. The proximal segment of maxilla is armed with one seta on protuberant inner distal corner vs. two setae on rounded corner; the second segment of the maxilla with one seta vs. two setae on inner margin. The aesthetascs on ultimate and penultimate segments of the antennules are unequal vs. equal in size. The pleotelson setae are moderately developed vs. greatly reduced. The setae on uropodal endopod are moderately developed vs. greatly reduced, and uropodal exopod stumpy vs. elongate.

Figures

FIGURE 1. Map showing the distribution of Habrobathynella ajraoi n. sp. (▲), H. parakrishna n. sp. (■), and H. pseudoindica n. sp. (♦).

FIGURE 9. Habrobathynella parakrishna n. sp., paratype male, habitus, lateral.

FIGURE 10. Habrobathynella parakrishna n. sp., holotype male (a – e), allotype female (f): (a) antennule, dorsal; (b) antenna, ventro-lateral; (c) labrum, ventral; (d) mandible, lateral; (e) pars incisiva, frontal; (f) paragnaths, ventral.

FIGURE 11. Habrobathynella parakrishna n. sp., holotype male (a, b), allotype female (c): (a) maxillule, lateral; (b) maxilla, lateral; (c) Th VIII, lateral.

FIGURE 12. Habrobathynella parakrishna n. sp., holotype male. (a – d) Th I – IV.

FIGURE 13. Habrobathynella parakrishna n. sp., holotype male. (a – c) Th V – VII.

FIGURE 14. Habrobathynella parakrishna n. sp., holotype male, Th VIII. (a) latero-external; (b) latero-internal; (c) anterior; (d) posterior; (e) ventral.

FIGURE 15. Habrobathynella parakrishna n. sp., holotype male (a), allotype (b – d): (a) pleotelson, lateral; (b) uropod, ventral; (c) uropodal exopod, lateral; (d) anal operculum, dorsal.