Parastenocaris edakkal, Totakura, Venkateswara Rao, Reddy, Yenumula Ranga & Shaik, Shabuddin, 2014

Totakura, Venkateswara Rao, Reddy, Yenumula Ranga & Shaik, Shabuddin, 2014, Three new species of Parastenocarididae (Crustacea, Copepoda, Harpacticoida) from India, Zootaxa 3821 (5), pp. 501-537 : 504-514

Parastenocaris edakkal n. sp.

( Figs 2–8 )

Type locality. Edakkal cave (11°37′54.0″N, 76°14′14.9″E, elevation 1233 m, water temperature 30ºC, pH 7.0) in Wayanad District of Kerala State in the Western Ghats, which constitute one of the key biodiversity hotspot areas of India ( Fig. 1 a). This Cave is not technically a cave, but rather a cleft or rift of about 20 m long, 6.7 m wide and 9.1 m deep fissure formed by a piece of rock (probably Kondalite) splitting away from the main body. On one side of the cleft is a huge rock covering the cleft to form the cave roof. Pictorial Stone Age carvings of human and animal figures and tools used by Neolithic man are seen inside the cave. These carvings are said to be as old as 5000-6000 B. C., suggesting the prehistoric civilization or settlement in this region (see http://www. edakkal .com/ index.htm). A small stream, probably originating from a perennial underground spring, flows through the length of the cave over fine sand deposit mixed with organic debris. There are no drippings from the rocky roof.

Type material examined. Holotype male ( MNHN –IU–2013–11244) and allotype female ( MNHN –IU–2013–11245) dissected on 3 slides each and 10 paratypes: 1 male ( MNHN –IU–2013–11246) and 1 female ( MNHN –IU–2013–11247) whole-mounted on 1 slide each, 1 male and 7 females in alcohol in a vial ( MNHN –IU–2013–11248). 0 9 May 2008, Coll. V. R. Totakura and Y. Ranga Reddy.

Description of adult male. Total body length, measured from tip of rostrum to posterior margin of caudal rami (excluding caudal setae), 368 Μm. Body heavily chitinized and pitted. Naupliar eye absent. Habitus ( Fig. 2 a, b) cylindrical and slender, without any podoplean demarcation between prosome and urosome; prosome/urosome ratio about 0.7 in dorsal view; greatest width in dorsal view falling in distal half of cephalothorax. Body length/ width ratio about 7.8. Free pedigerous somites without any lateral or dorsal expansions. All somites connected by well developed arthrodial membranes. Hyaline fringes of all somites smooth, very narrow and hard to distinguish from arthrodial membranes. Integument ornamented only with sensilla, cuticular pores, pits (no spinules), and also with sub-spherical, dorsal double-window on cephalothorax, and elliptical, dorsal simple cuticular window each on genital somite and next 3 somites, window on genital somite smallest. Pleural areas of cephalothorax moderately developed; cephalic appendages and coxae of legs 1–4 only partly exposed in lateral view. Rostrum ( Fig. 2 a, b) small, membranous, not demarcated at base, ornamented with 2 large dorso-lateral sensilla. Cephalothorax ( Fig. 2 a, b): subquadrate, about 1.2 times as long as wide in dorsal view, 1.3 times in lateral view, and representing 16% of total body length. Surface of cephalic shield ornamented with 4 pairs of large sensilla on anterior half as well as around cuticular double-window; window surface completely smooth, no cuticular pores discernible; second and third pedigerous somites as wide as posterior part of cephalothorax in dorsal view, with 3 and 2 pairs of sensilla (dorsal and lateral), respectively; third somite slightly shorter than second segment with 3 pairs of sensilla. Fourth pedigerous somite longer than preceding somite, with 3 pairs of sensilla (dorsal, lateral).

Urosome ( Figs. 2 a, b, 3a): first urosomite about as wide as fourth prosomite, but slightly shorter, ornamented with 3 pairs of sensilla dorsally ( Fig. 2 b) and also, 1 sensillum beside leg 5 ventrally ( Fig. 3 a), 1 pair of lobes in proximal-half ventrally ( Fig. 3 a). Genital somite slightly wider than first urosomite, with small, oval dorsal cuticular window in anterior half, also with 2 pairs of sensilla (dorsal, lateral) and 1 pair of sensilla (ventral) and 1 sensillum on either side of sixth legs. Third and fourth urosomites about as long as first urosomite but slightly narrower, with wider dorsal cuticular window each, and with 2 pairs of large posterior sensilla on distal half and 1 pair of sensilla disto-ventrally. Preanal somite narrower and slightly longer than fourth urosomite, with largest dorsal cuticular window, and without any surface ornamentation. Anal somite about 1.2 times as long as and slightly narrower than preanal somite, 1.2 times as long as its own width; ornamented with 1 pair of large dorsal sensilla and 1 antero-lateral cuticular pore proximally ( Fig. 2 a). A single large, longitudinally placed spermatophore discernible through cuticle of fourth and fifth segments, about 3.1 times as long as wide, kidneyshaped, with narrow curved neck. Anal operculum well developed, almost reaching posterior end of distal margin, with smooth and nearly straight distal margin, representing 73.3% of somite's width, unornamented on outer surface, transverse row of ventral spinules discernible through transparent operculum. Anal sinus wide open.

Caudal rami ( Figs. 2 a, b, 3a): divergent, cylindrical, gradually tapering posteriorly, about 3.3 times as long as greatest width in lateral view ( Fig. 2 a), 3.2 times in dorsal view ( Fig. 2 b), and about 0.6 times as long as anal somite, ornamented with 1 row of tiny spinules on ventral surface disto-laterally and with 1 distolateral pore, and armed with full complement of 7 setae (3 lateral, 1 dorsal, 1 subapical and 2 apical). Setae I–III thin, unequal, located as a group at about the middle of ramus. Dorsal seta (VII) slender and unipinnate, biarticulate basally, inserted closer to inner margin and opposite the level of setae I–III, about 0.6 times as long as caudal ramus. Inner apical seta (VI) smooth, proximally swollen, inserted close to ventral margin, about 0.6 times as long as ramus.

Middle apical seta (V) strongest, without breaking plane, unipinnate, with slightly curved tip. Outer subapical seta (IV) strong basally, also without breaking plane and unipinnate, about as long as ramus, inserted close to dorsal surface and directed laterally.

Antennule ( Fig. 5 a): 1.3 times longer than cephalothorax, slender, 8-segmented, and prehensile, ‘pocket-knife type’, digeniculate, proximal geniculation between third and fourth segments, and distal geniculation between sixth and seventh segments. First segment very short, ornamented with 1 row of spinules. Second one longest. Segments 4–6 moderately dilated, segment 5 without proximal spinous process on anterior surface; elongate aesthetasc with pointed tip, overreaching midlength of aesthetasc on ultimate segment, fused basally to 1 simple seta; shorter and slenderer apical aesthetasc on eighth segment, fused basally with 2 setae (acrotheck). Setal formula: 0.5.3.1.2+aes.0.1.8+aes. All setae slender, smooth except proximalmost seta on second segment, which is unipinnate, with long setules along outer margin. Length ratios of antennular segments, from proximal to distal end along caudal margin 1:2.2:0.8:0.3:1.7:0.5:0.7:1.1.

Antenna ( Fig. 5 b): relatively stout, composed of coxa, allobasis, 1-segmented endopod, and 1-segmented exopod. Coxa very short, ornamented with row of short spinule, and unarmed. Allobasis about 2.4 times as long as maximum width, unarmed, ornamented with 1 oblique row of spinules near mid-inner margin. Exopod small, cylindrical, about 2.3 times as long as wide, unornamented, armed with apical unipinnate seta, which is 2.8 times as long as segment. Endopod 0.6 times as long as allobasis and about twice as long as wide, surface frill occurring distally, ornamented with 1 large and 1 small arched spinular rows on inner margin, armed with 2 short bipinnate, unequal spines laterally and with 5 strong elements apically (2 subequal spines, 2 subequal geniculate setae and 1 unipinnate transformed seta).

Labrum ( Fig. 5 c): large, triangular in lateral view ( Fig. 4 a) and sub-ovate in ventral view, with narrow, concave, cutting edge finely denticulate, with short spinous projection on either side; also, ornamented with 1 row of arched spinules on ventral surface close to cutting edge.

Mandible ( Fig. 5 d): cutting edge narrow on elongate coxa, armed with 2 complex teeth ventrally, 1 unipinnate seta dorsally, and several smaller teeth. Palp 1-segmented, cylindrical, about 3 times as long as wide, unornamented, and armed apically with 2 smooth, unequal apical setae.

Maxillule ( Fig. 5 e): with relatively large praecoxa, arthrite rectangular, about 3.3 times as long as wide in lateral view, armed with lateral stout curved seta, and 3 apical claws of which middle one with serrulate outer margin. Coxal endite armed with 2 smooth, unequal setae apically. Basis 1.3 times longer than coxal endite, armed with 1 strong and 2 slender smooth apical setae.

Maxilla ( Fig. 5 f): composed of syncoxa, basis, and 1-segmented endopod. Syncoxa with 2 endites, proximal one short, armed with 2 smooth unequal setae apically, distal endite armed with 1 spiniform and 1 smooth setae apically. Allobasis prolonged into strong, unipinnate claw, without seta at base. Endopod represented by small segment, armed with 2 smooth apical setae.

Maxilliped ( Fig. 5 g): with short and relatively strong syncoxa, unornamented and unarmed; basis slender, 2.5 times as long as wide and 2.1 times as long as syncoxa, unornamented and unarmed; endopod small with unipinnate claw, 0.6 times as long as basis.

Legs 1–4 ( Figs. 6 a–c, 7a): praecoxa and intercoxal sclerite of all legs smooth and unarmed.

Leg 1 ( Fig. 6 a): coxa trapezoidal; ornamented with a row of small spinules on antero-distal surface. Basis trapezoidal, somewhat shorter than coxa, ornamented with 1 row of spinules on outer margin and 1 ventral row at base of endopod and another row of small spinules on inner margin, armed with 1 slender seta on outer margin and 1 spiniform seta on inner margin. Exopod 3-segmented, ornamented with 1 row of spinules along outer margins of all segments, second segment with 1 row of spinules at inner distal corner. First segment 0.7 times as long as next 2 segments combined, armed with 1 outer bipinnate spine; second segment unarmed and with 4 elements on third segment (1 outer spine, 1 apical seta and 2 apical geniculate setae). Endopod 2-segmented, about as long as exopod; first segment about as long as first 2 exopodal segments combined, 3.3 times as long as wide, unarmed, ornamented with 1 transverse row of elongate spinules on inner margin and 2 arched rows (1 dorsal, 1 ventral) of large spinules on outer margin; second segment ornamented with 1 row of spinules on outer margin, and armed apically with 1 long geniculate seta and 1 spine; endopodal geniculate seta 1.6 times as long as entire endopod, about as long as innermost geniculate seta on exopod (but almost straight). All exopodal and endopodal armature elements unipinnate along outer margin except bipinnate spine on first exopodal segment.

Leg 2 ( Fig. 6 b): coxa ornamented with 2 arched rows of spinules near outer distal corner (1 dorsal and 1 ventral). Basis rhomboidal, slightly smaller than coxa, unarmed, ornamented with 1 row of large spinules along outer margin. Exopod 3-segmented; ornamented with 1 row of spinules along outer margins of all segments, hyaline frill each at inner distal corner of first and third exopodal segments, but second segment with 1 row of spinules instead. First segment 0.7 times as long as next 2 segments combined, armed with large, bipinnate outer spine on first segment; second segment unarmed; third segment 1.3 times as long as second segment, armed with 3 long elements, 1 subapical spine and 2 apical bipinnate setae; innermost seta about 1.2 times as long as exopod. Endopod 1-segmented, spatulate and almost 4.1 times as long as wide, 0.6 times as long as first exopodal segment in length, ornamented with 3 large spinules apically, and armed with 1 smooth seta apically, which is 0.7 times as long as segment.

Leg 3 ( Fig. 7 a): coxa rhomboidal, smaller than basis, ornamented with arched row of spinules near inner margin ventrally. Basis robust, ornamented with 1 oblique row of large spinules at distal outer corner, 1 ventral row near inner margin and 1 pore on anterior surface, and armed with moderately long, slender seta on outer margin. Endopod represented by 1 small, curved seta, inserted on inner margin at distal third of basis length. Exopod 2- segmented, perfectly fused with each other; ancestral proximal segment moderately strong, nearly thrice as long as basal width and somewhat bent inwards; proximal region somewhat dilated and ornamented with 1 spinule on outer margin and 1 row of 3 spinules at outer distal corner; ancestral second segment (apophysis) short, unornamented, bent inwardly and armed apically with 2 modified, unequal elements ( Fig. 7 c): inner element ladleshaped with hyaline structure on inner margin, and outer one hyaline, bulbous at base and gradually tapering distally. Thumb distinct at base and modified into curved digitiform chitinized structure, as long as apophysis.

Leg 4 ( Fig. 6 c, d): coxa rhomboidal, ornamented with 1 row of spinules near distal margin. Basis trapezoidal, ornamented with 1 row of spinules and 1 pore on anterior surface, and armed with moderately long seta on outer margin. Exopod 3-segmented, somewhat bent inwards, ornamented with 1 row of long spinules along outer margins of all segments; hyaline frills at inner distal corner of first and third segments, but second segment with 1 row of spinules. First segment nearly 0.7 times as long as next 2 segments combined, armed with single, strong bipinnate outer spine subdistally; second segment 0.7 times as long as third segment; third segment armed with outer spine and long apical, bipinnate seta; seta 1.6 times as long as spine, 2.4 times as long as third exopodal segment, 0.9 times as long as entire exopod. Basal chitinous complex consisting of large sclerotized plate with 1 small hyaline lobe mid-distally and 1 large hyaline lobe at outer distal angle; 1 sturdy, hook-like spine at inner distal corner. Endopod 1.3 times as long as first exopodal segment, membranous and ventricose in outline, with proximal part bulbous, ornamented with 1 row of spinules and drawn out distally into biserrulate, pointed structure.

Leg 5 ( Figs. 3 a, 7d): small, simple, trapezoidal plate, and fused at base; ornamented with 1 group of 2–3 tiny spinules on inner margin, 1 small cuticular pore subproximally; distal part expanded and palmate; inner distal corner produced into rather short spiniform process. Basal seta long, articulate at base and arising from lobed projection; inner lobe with 2 unequal, smooth setae (probably ancestral endopodal armature), outer seta 0.7 times as long as inner seta.

Leg 6 ( Figs. 2 a, 3a): smooth, unarmed, forming simple operculum covering gonopore, fused with sixth pedigerous somite, elliptical in ventral view.

Description of adult female. Body length excluding caudal setae 385–405 Μm (397 Μm in allotype). Habitus ( Fig. 4 a): ornamentation of prosomites, colour and naupliar eye similar to male, except genital and first abdominal somites fused into double-genital somite.

Genital double-somite ( Fig. 4 b): genital apertures covered by vestigial sixth legs; median copulatory pores also covered by fused sixth legs; seminal receptacles small; copulatory duct very short and weakly sclerotized. Third urosomite, preanal somite, and anal somite very similar to male.

Caudal rami ( Figs. 3 b, 4a, b): 0.7 times as long as anal somite, about 3.2 times as long as wide in dorsal and ventral views, gradually tapering, with armature and ornamentation as in male.

Antennule ( Figs. 4 a, 8e): 7-segmented, first segment short, ornamented with 1 row of spinules on ventral surface; second segment longest; fourth segment with elongate, moderately thick aesthetasc, extending up to the tip of aesthetasc on segment 7; aesthetasc on segment 7 slender and fused basally to 2 apical setae (acrotheck); setal formula: 0.4.2.2+aes.0.0.9+aes. All setae, except unipinnate proximalmost one on segment 2, smooth. Length ratio of antennular segments from proximal to distal end along caudal margin 1.0: 3.0:1.4: 1.7: 0.7: 0.7: 1.5.

Antenna, labrum, mandible, maxillule, maxilla and maxilliped similar to male.

Leg 1 ( Fig. 8 a): coxa trapezoidal, with arched row of spinules near proximal outer corner, basis also trapezoidal, with 3 rows of spinules and armed with only outer seta. Other details as illustrated.

Leg 2 ( Fig. 8 b): coxa trapezoidal, ornamented with 1 arched row of spinules at distal inner corner and 1 row of spinules ventrally; basis smaller than coxa, ornamented with 1 row of spinules on outer margin. Exopod same as in male. Endopod somewhat dilated at about midlength; ornamentation and armature same as in male in different views ( Fig. 8 f–i).

Leg 3 ( Fig. 8 c): coxa ornamented with 1 arched row of spinules near posterior margin. Basis ornamented with 1 row of spinules on outer margin; armed with 1 long and smooth outer seta. Exopod 2-segmented, ornamented with large spinules along outer margin, both segments with hyaline frill each at inner distal corner; first segment armed with 1 outer spine; second segment with 1 outer spine and 1 apical seta; seta 1.8 times as long as spine; all elements bipinnate. Endopod 1-segmented, slender, almost as long as first exopodal segment, tapering to pointed tip and with spinulose disto-lateral margins.

Leg 4 ( Fig. 8 d): endopod strong, lanceolate, bent inwards, 1.6 times as long as first exopodal segment together with apical biserrulate spine fused at base; 1 large spinule occurring at about mid-inner margin; other details as illustrated.

Leg 5 ( Fig. 4 b, c): fused at base; small, simple, trapezoidal plate, ornamented with 1 small cuticular pore subproximally; subdistal part expanded and inner distal corner produced into moderately long spiniform process. Armature elements same as in male, outer seta 0.8 times as long as inner seta.

Leg 6 ( Fig. 4 b): vestigial, fused into simple cuticular flap, covering gonopores; unornamented and unarmed.

Etymology. The specific epithet, alluding to the type locality, Edakkal Cave; proposed here as a noun in apposition to the generic name.

Distribution. This species is only known from the type locality.

Ecology. Parastenocaris edakkal n. sp. was accompanied by Proserpinicaris corgosinhoi n. sp. and strays of nematodes. This species was collected at a relatively high elevation of 1233 m, whereas its congeneric Indian cavernicole, Parastenocaris kotumsarensis , occurred at an altitude of 560 m. Even Parastenocaris sutlej from a Himalayan river was collected at an altitude of 656 m. Other hyporheic Indian species occur somewhat close to the sea level.

Variation. Shape of leg 2 endopod ( Fig. 8 f–i) varying depending on the angle of view.

Figures

FIGURE 1. (a) Map showing the distribution of the Indian parastenocaridid species including Parastenocaris edakkal n. sp., Proserpinicaris corgosinhoi n. sp., and Proserpinicaris karanovici n. sp.; (b) sampling of a farm bore.

FIGURE 2. Parastenocaris edakkal n. sp., paratype male: (a) habitus, lateral view; (b) habitus, dorsal view.

FIGURE 3. Parastenocaris edakkal n. sp., (a) holotype male, urosome, ventral view; (b) allotype female, urosome, dorsal view.

FIGURE 4. Parastenocaris edakkal n. sp., paratype female (a, c), allotype female (b): (a) habitus, lateral view; (b) urosome, ventral view; (c) leg 5, latero-ventral view.

FIGURE 5. Parastenocaris edakkal n. sp., holotype male: (a) antennule, dorsal view; (b) antenna, lateral view; (c) labrum, ventral view; (d) mandible, lateral view; (e) maxillule, lateral view; (f) maxilla, lateral view; (g) maxilliped, lateral view.

FIGURE 6. Parastenocaris edakkal n. sp., holotype male: (a) leg 1, anterior view; (b) leg 2, anterior view; (c) leg 4, anterior view; (d) leg 4 endopod, antero-lateral view.

FIGURE 7. Parastenocaris edakkal n. sp., holotype male (a, d), paratype male (b, c): (a) leg 3, anterior view; (b) leg 6, ventral view; (c) apophysis of leg 3; (d) leg 5, ventral view view.

FIGURE 8. Parastenocaris edakkal n. sp., allotype female: (a) leg 1, posterior view; (b) leg 2, anterior view; (c) leg 3, posterior view; (d) leg 4, posterior view; (e) antennule, dorsal view; (f – i) leg 2 endopod; (j, k) leg 3 endopod.