Ancylocheles peterngi, Trivedi & Osawa & Vachhrajani, 2017

Trivedi, Jigneshkumar N., Osawa, Masayuki & Vachhrajani, Kauresh D., 2017, A new species of the genus Ancylocheles Haig, 1978 (Crustacea: Decapoda: Anomura: Porcellanidae) from Gujarat, northwestern India, Zootaxa 4299 (3), pp. 384-390 : 385-389

Ancylocheles peterngi n. sp.

( Figs. 1–4 )

Material examined. Holotype: ovigerous female (CL 3.06 mm, CW 3.01 mm), Shivrajpur, Gujarat State, India, 21°19'55"N, 68°57'02"E, coral reef, 16 October 2016, coll. Jignesh Trivedi, ZL-AR-CR-18 . Paratypes: 3 males (CL 3.69–3.96 mm, CW 3.45–3.68 mm), 1 female (CL 2.43 mm, CW 2.20 mm), Shivrajpur , Gujarat State, India, 21°19'55"N, 68°57'02"E, coral reef, 3 January 2016, coll. Barkha Purohit and Jignesh Trivedi, ZL-AR-CR-19. Non types: 3 males (CL 3.82–4.08 mm, CW 3.62–3.88 mm), 6 females (CL 3.07–4.27 mm, CW 2.77–4.17 mm, Shivrajpur, Gujarat State, India, 21°19'55"N, 68°57'02"E, coral reef, 16 October 2016, coll. Jignesh Trivedi, ZL- AR-CR-20.

Description. Carapace ( Fig. 1 A) approximately as long as broad, pentagonal in general outline, with many transverse striae anteriorly bearing minute setae except on metagastric and cardiac regions; regions moderately defined; protogastric ridge distinct, with row of short setae. Rostrum broad, triangular, anteriorly bent, with subacute apex; anterior margin serrated (denticles decreasing in size towards apex), with row of dense short setae; dorsal surface with shallow median groove extending to protogastric ridge. Orbits moderately deep; inner orbital margin terminating bluntly; supra-orbital margin strongly concave; outer orbital angle produced, terminating in minute spine. Hepatic margins moderately convex, with 4 small spines. Cervical grooves distinctly demarcated. Branchial margins slightly convex; epibrachial margin minutely denticulate; mesobrachial margin nearly straight, with 3 small spines decreasing in size posteriorly.

Third thoracic sternite ( Fig. 2 E) trilobate; median lobe broad, rounded on anterior margin; lateral lobes produced bluntly, not reaching anterior margin of median lobe. Fourth thoracic sternite with anterior margin moderately concave.

Telson ( Fig. 1 B) composed of 7 plates; median plate largest, proxiomolateral plates smallest.

Ocular peduncles ( Fig. 1 A) moderately small, dorsal extension onto cornea weakly produced, hardly visible in dorsal view.

Basal article of antennular peduncle ( Fig. 1 C) approximately as long as broad; anterior margin minutely dentate, with 1 large tooth mesially and some smaller teeth laterally; ventral surface nearly smooth, with long transverse ridge submedially; mesial margin with slender spine distally.

Antennal peduncle ( Fig. 1 D) short, slender, nearly smooth; movable (second to fourth) articles excluded from orbit by projection of immovable (first) article pressed to anterior margin of carapace. First article largest, longer than broad; lateral surface slightly concave; anterior margin minutely serrated. Second article short, rounded; anterior margin slightly serrated. Third article subrectangular; anterior margin slightly dentate, with small tubercle distally. Fourth article shortest, rounded.

Third maxilliped ( Fig. 2 D) moderately slender. Coxa slightly longer than broad; dorsal margin smooth; ventral margin also smooth, with narrow distal projection. Basis articulating with ischium, subtriangular. Ischium suboval, with numerous striae on lateral surface; dorsal margin with narrow, sharply pointed distal projection; ventrodistal margin convex. Merus longer than broad; lateral surface with short transverse striae; dorsal margin smooth, distally rounded; ventral margin with broad, subrectangular lobe. Carpus with undulated striae on lateral surface; dorsal margin smooth; ventral margin with low triangular projection on median part. Propodus slender; dorsal margin nearly straight; ventral margin slightly convex. Dactylus short, subtriangular; dorsal margin straight, smooth. Merus to dactylus with long setae on ventral margins, setae on dactylus reaching anterior margin of coxa.

Chelipeds ( Fig. 3 A–D) (first pereopods) somewhat unequal in size, but generally similar to each other and between male and female in shape and armature; dorsal surface covered with long and short striae, small pits, and scattered small tubercles, all bearing minute setae. In larger cheliped ( Fig. 3 A, C), merus with distinct rounded lobe distally on anterior margin, margin of lobe denticulate, with 4 or 5 small but distinct spines; dorsal surface medially with long striae running parallel to dorso distal margin; ventral surface covered with small pits. Carpus 1.2 times as long as broad; proximal half of dorso-anterior margin with 2 blunt or acute lobes separated by shallow notch, anterior margins of lobes slightly or distinctly denticulate; dorsal surface with 3 longitudinal crests running parallel to each other, continued to dorsodistal margin, and with scattered, moderately long setae, each crest running along anterior and posterior margins and on midline. Chela moderately broad, 1.6 times as long as carpus, 1.8 times longer than broad; dorsal surface of palm with long, oblique striae and with elevated, blunt median crest reaching base of fixed finger at most; scattered, short striae present on median crest; shallow, broad groove running parallel to posterior marginal crest, with short setae; anterior margin thin, minutely crenulate; posterior margin nearly smooth; ventral surface covered with small pits. Small or large hiatus present between fixed finger and dactylus. Fixed finger nearly equal in length to dactylus, with no distinct teeth on cutting edge; dorsal surface with short striae; posterior margin thin, minutely serrated. Dactylus nearly equal in length to palm measured on posterior margin, moderately curved distally, terminating in blunt claw; dorsal surface with short to moderately long striae; cutting edge smooth, with no distinct teeth; ventral surface with small pits in proximal half.

Smaller cheliped ( Fig. 3 B, D) with scattered striae bearing short setae on dorsal surface. Carpus with 3 longitudinal crests on dorsal surface, weaker than those of larger cheliped. Palm with shallow groove lined with short setae, narrower than that of large cheliped and running parallel to posterior marginal crest. Dactylus and fixed finger without distinct teeth on each cutting edge; ventral surface of cutting edge of dactylus with or without tuft of dense setae.

Ambulatory legs (second to fourth pereopods; Fig. 2 A–C) stout, subcylindrical, with scattered setae on margins, setae longer on dorsal margins of carpus and propodus; lateral surfaces with scattered, short striae bearing minute setae. Meri somewhat compressed, elongate subrectangular, decreasing in size posteriorly; dorsal margin slightly crenulate, dorsodistal angle with tuft of long setae on fourth pereopod but naked or with few short setae on second and third pereopods; ventral margin nearly smooth, more convex on second and third pereopods than fourth. Carpi moderately long; dorsal margin with short striae giving undulating appearance, unarmed; ventral margin nearly smooth. Propodi 1.2 times as long as dactyli; dorsal margin slightly crenulate; laterodistal margin subacute or rounded; ventral margin with 3 or 4 (3 on fourth pereopod in holotype) corneous spines, spines increasing in size distally; distoventral margin mesially with additional spine. Dactyli each terminating in curved, sharp claw; dorsal margin smooth; lateral surface with few, moderately long setae near tip of claw; ventral margin with 4 corneous spines increasing in size distally.

Variation. The morphology of the larger cheliped varies between the largest male (CL 4.08 mm, CW 3.71 mm) and the smallest female (CL 2.43 mm, CW 2.20 mm) examined. The carpus and palm have more prominent, dorsal grooves in the largest male than in the smallest female. The lobes on the dorso-anterior margin of the carpus are marginally rounded and minutely denticulate in the largest male, instead of acute and prominently denticulate in the smallest female. In males with CL larger than 3.5 mm, one chela is distinctly larger than another, but in females larger than 2.4 mm, both chelae are subequal in size. The morphology of the smaller cheliped also varies between male and female. The hiatus of the fingers of the smaller chela is covered with thick tuft of setae in males, while such tuft was not observed in smaller chela of females.

Coloration in life ( Fig. 4 ). Carapace generally light to dark brown; frontal region light cream; mesogastric, protogastric, hepatic, and epibranchial regions with dark brown patches; cardiac region dark orange; cream rounded spot with tuft of cream colored short setae present on either side of epibranchial regions. Antennal peduncle and flagellum cream, with dark brown bands. Third maxilliped cream. Chelipeds light brown, with dark brown spots and patches on dorsal surface; large cream band on articulation between chela and carpus; fingers dark brown, with tips and cutting edges cream; ventral surface of cheliped entirely cream. Ambulatory legs cream, with dark brown bands on median parts of meri, carpi, and propodi; dactyli white in each distal half, with dark brown claw. Abdomen light cream, with scattered dark brown spots.

Habitat. Coral reef, under rocks; low intertidal.

Distribution. Presently known only from the type locality, Shivrajpur located on the coastal region of the Dev Bhumi Dwarka District (part of Saurashtra), Gujarat, India.

Etymology. The new species is named in honor of Dr. Peter K. L. Ng of the Lee Kong Chian Natural History Museum, National University of Singapore, for his great contribution in taxonomy and biology of various crustaceans including new taxa described from India.

Remarks. The present new species is assigned to the genus Ancylocheles based on the following characters: carapace being approximately as long as broad, with regions defined but not strongly areolate; rostrum broadly triangular in dorsal view; antennal peduncle with movable (second to fourth) articles excluded from orbit by projection of immovable (first) article pressed to anterior margin of carapace; and chelipeds being generally unequal in size and not showing pronounced sexual dimorphism in armature as well as in degree of distortion of fingers ( Haig 1978; Osawa 2007). Although Haig (1978) mentioned an eastern Atlantic species Porcellana foresti Chace, 1956 appears to be related to A. gravelei , the former species is clearly different from the latter by the trilobate rostrum and chelipeds without any distinct sculptures on the dorsal surface ( Chace 1956; also see a note by Osawa & McLaughlin 2010: 118).

Although we could not unfortunately examine the holotype of A. gravelei which is deposited in the collection of the Zoological Survey of Indian Museum, Kolkata, the present new species is distinguishable from A. gravelei by several characters. The carapace front is more strongly produced in dorsal view and the supraorbital margin is much more strongly concave in the new species than in A. gravelei . The median lobe of the third thoracic sternite is strongly convex on the anterior margin in A. peterngi n. sp., whereas it has a rather transverse anterior margin in A. gravelei . The second article of the antennal peduncle is unarmed on the anterior margin in the new species, instead of having a small but distinct spine at the antero distal angle in A. gravelei . The ventral lobe of the merus of the third maxilliped is subrectangular in A. peterngi n. sp., rather than rounded in A. gravelei (for morphology of A. gravelei , see Sankolli 1963; Haig 1965; Tirmizi et al. 1989; Hiller et al. 2010).

Figures

FIGURE 1. Ancylocheles peterngi n. sp., holotype female (CL 3.06 mm, CW 3.01 mm), ZL-AR-CR- 18. A, carapace, dorsal view; B, telson, external view; C, basal segment of left antennular peduncle, ventral view; D, left antennal peduncle, lateral view.

FIGURE 2. Ancylocheles peterngi n. sp., holotype female (CL 3.06 mm, CW 3.01 mm), ZL-AR-CR- 18. A, left second pereopod, lateral view; B, left third pereopod, lateral view; C, left fourth pereopod, lateral view; D, left third maxilliped, lateral view; E, third thoracic sternite, ventral view.

FIGURE 3. Ancylocheles peterngi n. sp., holotype female (CL 3.06 mm, CW 3.01 mm), ZL-AR-CR- 18 (A, B); paratype male (CL 3.79 mm, CW 3.58 mm), ZL-AR-CR- 19 (C, D). A, C, larger cheliped, dorsal view; B, D, smaller cheliped, dorsal view.

FIGURE 4. Ancylocheles peterngi n. sp., paratype female (CL 2.43 mm, CW 2.20 mm), ZL-AR-CR- 19. Entire animal, dorsal view.