Orcovita hicksi, Davie & Ng, 2012

Davie, Peter J. F. & Ng, Peter K. L., 2012, Two New Species Of Orcovita (Crustacea: Decapoda: Brachyura: Varunidae) From Anchialine Caves On Christmas Island, Eastern Indian Ocean, Raffles Bulletin of Zoology 60 (1), pp. 57-70 : 62-65

Orcovita hicksi , new species

( Figs. 2 , 3 , 6C, 6D , 7 , 8 , 9 C–E, 10B, 11E–I, 12)

Material examined. — Holotype: male (17.4 × 13.2 mm) (WAM- C49450), field no. BES14437, Whip Cave , Waterfall Road, Christmas Island, 10°25'22.0"S, 105°42'04.4"E, coll. R Anderson, 8 May 2006 — Paratypes: 1 female (14.2 × 10.8 mm) ( WAM-C49451 ), same data as holotype — 1 immature female (15.2 × 11.9 mm) (QM- W29117), station CI-14, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, Xmas Island Expedition 2010 — 1 male (14.4 × 11.3 mm), 2 females (larger 20.8 × 15.9 mm) ( ZRC 2012.0073 ), station CI-14, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 27 Jan.2010 — 1 male, 1 female ( QM-W29118 ), station CI-15, Runaway Cave , Waterfall Road, 10°25.386'S, 105°42.063'E, coll. Xmas Island Expedition 2010, 27 Jan.2011 — 2 females ( QM-W29119 ), station CI-17, Runaway Cave , Waterfall Road, 10°25.386'S, 105°42.063'E, coll. Xmas Island Expedition 2010, 28 Jan.2010 — 1 male ( ZRC 2012.0074 ), station CI-18, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 28 Jan.2010 — 1 male (16.4 × 13.8 mm) ( ZRC 2012.0075 ), station CI-30, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 02 Feb.2010 — 1 male (23.5 × 17.3 mm) ( ZRC 2012.0076 ), station CI-10, Freshwater Cave , near The Blowholes, 10.51325°S, 105.62421°E, coll. Xmas Island Expedition 2011, 22 Mar.2011 — 3 females ( ZRC 2011.0077 ), station CI-10, Freshwater Cave , near The Blowholes, 10.51325°S, 105.62421°E, coll. Xmas Island Expedition 2011, 22 Mar.2011 — 2 females ( ZRC 2011.0079 ), station CI-12, 19 th Hole Cave , next to Christmas Island Golf Course, 10.42488°S, 105.70123°E, 19 th Hole, near Golf Course, coll. Xmas Island Expedition 2011, 22 Mar.2011 — 1 male (15.9 × 12.2 mm) ( ZRC 2012.0080 ), station CI-12, 19 th Hole Cave , next to Christmas Island Golf Course, 10.42488°S, 105.70123°E, coll. Xmas Island Expedition 2011, 22 Mar.2011 — 5 males (largest 21.2 × 15.9 mm) ( ZRC 2012.0066 ), station CI-14, Freshwater Cave , near The Blowholes, 10.51325°S, 105.62421°E, coll. Xmas Island Expedition 2011, 23 Mar.2011 — 4 males (largest 19.7 × 15.3 mm), 1 female (18.3 × 14.3 mm) ( QM-W29218 ), station CI-19, Runaway Cave , Waterfall Road, 10°25.386'S, 105°42.063'E, coll. Xmas Island Expedition 2011, 24 Mar.2011 — 1 male, 1 female ( QM-W29225 ), station CI-35, Freshwater Cave , near The Blowholes, 10.51325°S, 105.62421°E, coll. Xmas Island Expedition 2011, 28 Mar.2011 — 1 male (16.3 × 12.5 mm), 1 female (19.9 × 14.8 mm) ( WAM-C49452 ), field no. BES11648, Whip Cave , 10°25.377'S, 105°42.081'E, coll. R. D. Brooks, 19 Jun.2004 — 1 male (15.0 × 11.4 mm) (WAM- C49453), field no. BES14439, 19 th Hole Cave , next to Christmas Is. Golf Course, 10°25'30.0"S, 105°42'04.2"E, coll. R Anderson, 19 May 2006 . All localities in Christmas Island .

Description. — Carapace subrectangular to subovate ( Figs. 2A , 3 , 7 , 8A ), distinctly broader than long (width to length ratio ca. 1.25), dorsal surface mostly smooth, glabrous, finely punctate, but becoming finely granular anteriorly and anterolaterally, especially in females; regions mostly poorly defined, gastro-cardiac groove deeply grooved laterally; postfrontal lobes obsolete; cervical grooves indistinct, shallow, broad; epigastric cristae low, indistinct; short, low ridge present adjacent to junction between posterolateral margin and posterior carapace margin. Anterolateral margin lined with distinct, rounded granules; not clearly demarcated from posterolateral margin; exorbital angle very broad, separated from single epibranchial tooth by rounded sulcus; posterolateral margins straight or weakly concave, clearly converging posteriorly; posterior carapace margin straight; supraorbital margin granulate, medially moderately convex, inner margins obliquely convergent towards frontal margin; frontal margin dorsally ( Fig. 8A, B ) appearing broadly concave, defined by transverse ridge of granules; true frontal margin almost vertically deflexed, sinuous, concave medially, separated from dorsal granular ridge by relatively wide strip tapering laterally; infraorbital margins incomplete, median lobe low, convex, coarsely granulate, separated from exorbital tooth by deep sinus; strong row of rounded granules below infraorbital margin on suborbital region, extending to sub-branchial region ( Fig. 8B ). Antennal segments entering orbital hiatus. Antennules broad; interantennular septum broad. Eyes well-developed, cornea pigmented. Epistome ( Figs. 8B , 10B ) relatively narrow, posterior margin with 2 lateral clefts, median part broadly triangular, margin finely granular. Third maxilliped ( Figs. 8B , 10B ) with broad, stout exopod, exopod 0.9 times width of ischium, flagellum well developed; ischium stout (length to width ratio ca. 1.9, measured along outer edge), surface smooth, bearing scattered very short setae, outer margin minutely granulate; merus broad (length to width ratio ca. 1.4), antero-external margin minutely granular, markedly auriculiform.

Chelipeds relatively long, surface of segments smooth. Male chelae swollen, subequal; surface very finely granular; fingers as long as palm; with a small but distinct pulvinus at base of fingers, some very short setae around pulvinus but otherwise naked ( Fig. 6C, D ). Merus sharply trihedral, upper inner margin finely granulate, ventral margins more coarsely granular. Carpus rounded, smooth, inner distal angle finely dentate. Female chelae similar to those of male but smaller.

Ambulatory legs somewhat dorsoventrally flattened, all segments long, slender; second and third ambulatory legs equal longest; upper and lower surfaces mostly smooth. Meri with upper and lower borders finely serrated; proximal upper surface granular; anterior margin of merus with blunt subdistal lobe. Outer surface of carpus smooth, lacking setae; anterior and posterior margins of propodus with small clumps of long and short setae, respectively; dactylus tapering to slender, acute tip. Dactyli rectangular in cross section, upper and lower margins fringed with dense short setae; 3M long, slender (length to width ratio 5.6), 3P long, slender (length to width ratio 4.8), 3D very long, slender (length to width ratio 11.0); 4M long, slender (length to width ratio 4.5), 4P long (length to width ratio 2.4), 4D long, slender (length to width ratio 6.4).

Male abdomen narrowly triangular ( Fig. 9C ); lateral margins edged with very short, dense setae interspersed with several long, stiff setae; first abdominal somite widest, slightly wider that third, weakly arched, with transverse ridge; second abdominal somite reduced to short strip, slightly narrower than third; third abdominal somite broad, weakly convex laterally; fourth abdominal somite broader but shorter than fifth abdominal somite; fifth abdominal somite with proximal and distal margins straight, lateral margins convergent; sixth abdominal somite rectangular 2.2 times wider than long, lateral margins weakly convex distally, proximal margin straight; telson about as long as wide, lateral margins subparallel, broadly rounded distally. Female abdomen very broad, covering most of thoracic sternum ( Fig. 9D ).

Male thoracic sternum ( Fig. 9C ) generally smooth, punctate; lateral margins of first 2 thoracic sternites armed with large smooth granules; triangular part of sternites 1 and 2 with patch of long dark setae inside medial excavation; suture between sternites 2 and 3 relatively straight; lateral margins of sternites 3 and 4 sinuous, with deep, broad notch and granulate lobe, indicating edge of fused suture; deep narrow median longitudinal groove between sternites 7 and 8. Female thoracic sternum similar in form but relatively broader. G1 ( Fig. 11 E–H) slender, weakly curving outwards, reaching to anterior margin of sternite 5; terminal lobe elongate; genital opening lateral to base of terminal lobe; subterminal lobe pectinated, elongate, densely setose. G2 short, small ( Fig. 11I ). Vulva raised, convex, oval ( Fig. 9E ).

Colour. — Smaller specimens (up to ca. 16 mm in carapace width) tend to be yellowish-white to orange ( Fig. 3A, B ). When they exceed this size, both males and females become more whitish, and the anterior half of the carapace is covered with scattered brown spots and blotches ( Figs. 2A, 2B , 3C ). The chela also becomes almost white ( Fig. 2C ).

Etymology. — Named for John Hicks who was the Australian Government Conservator on Christmas Island from 1979 to 1983. His book “Christmas Crabs”, written with the late Holger Rumpff and Hugh Yorkston, did much to publicise this unique crab fauna to the eyes of the world, and could only have been written by one who was as thoroughly entranced by the Christmas Crabs, as we are ourselves.

Remarks. — Orcovita hicksi , new species, can easily be separated from O. orchardorum , new species, and its close allies O. miruku and O. holthuisi , by its single epibranchial tooth (vs. two epibranchial teeth present in the latter species) and the absence of a tuft of setae at the base of cheliped fingers in males (vs. present in the latter three species) (see Remarks for O. orchardorum , new species). It can be separated from its closest long-legged relatives (see discussion of Groups I and II later) by the new key presented here.

Habitat. — See comments for Orcovita orchardorum , new species.

Figures

Fig. 2. Orcovita hicksi, new species. Colours in life, paratype male (23.5 × 17.3 mm) (ZRC 2012.0076), station CI-14, 2011. A, overall dorsal view; B, frontal view of carapace; C, outer view of left chela.

Fig. 3. Orcovita hicksi, new species. Colours in life, overall dorsal views.A, paratype male (15.9 × 12.2 mm) (ZRC 2012.0080), station CI-12, 2011; B, paratype male (14.4 × 11.3 mm) (ZRC 2012.0073), station CI-14, 2010; C, paratype female (20.8 × 15.9 mm) (ZRC 2012.0073), station CI-14, 2010.

Fig. 6. Male left and right chelae.A,B, Orcovita orchardorum, new species, holotype male (21.0 × 16.7 mm) (QM-W29114). C, D, Orcovita hicksi, new species, holotype male (17.4 × 13.2 mm) (WAM-C49450).

Fig. 7. Orcovita hicksi, new species, dorsal view. A, holotype male (17.4 × 13.2 mm) (WAM-C49450); B, paratype female (15.2 × 11.9 mm) (QM-W29117).

Fig. 8. Orcovita hicksi, new species, holotype male (17.4 × 13.2 mm) (WAM-C49450). A, carapace; B, frontal view.

Fig. 9. Sternal view showing male and female abdomens. Orcovita orchardorum, new species: A, holotype male (21.0 × 16.7 mm) (QM- W29114); B, paratype female (18.9 × 15.2 mm) (QM-W29115). Orcovita hicksi, new species: C, holotype male (17.4 × 13.2 mm) (WAM- C49450); D, E, paratype female (20.8 × 15.9 mm) (ZRC 2012.0073), station CI-14, 2010.

Fig. 10. Frontal view showing epistome, frontal and anterolateral margins andorbital andsuborbital margins.A, Orcovita orchardorum, new species, holotype male (21.0 × 16.7 mm) (QM-W29114). B, Orcovita hicksi, new species, holotype male (17.4 × 13.2 mm) (WAM-C49450).

Fig. 11. Male gonopods (denuded). Orcovita orchardorum, new species, holotype male (21.0 × 16.7 mm), (QM-W29114): A–C, abdominal and sternal views of G1, D, G2; Orcovita hicksi, new species, holotype male (17.4 × 13.2 mm) (WAM-C49450): E–H, abdominal and sternal views of G1, I, G2.