Orcovita Ng & Tomascik, 1994

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: 58-62

publication ID

http://doi.org/10.5281/zenodo.4508467

persistent identifier

http://treatment.plazi.org/id/6D6787A1-FF8E-0E6F-FEF4-FAE1FD00FC79

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Carolina

scientific name

Orcovita Ng & Tomascik, 1994
status

new species

Orcovita Ng & Tomascik, 1994   Orcovita orchardorum   , new species

( Figs. 1 View Fig , 4 View Fig , 5 View Fig , 6A, 6B View Fig , 9A, 9B View Fig , 10A View Fig , 11 View Fig A–D, 12)

Material examined. — Holotype: male (21.0 × 16.7 mm) (QM- W29114 View Materials ), station CI-14, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 27 Jan.2010 GoogleMaps   . Paratypes: 1 male (15.5 × 12.5 mm), 1 female (18.9 × 15.2 mm) ( QM-W29115), same data as holotype GoogleMaps   — 3 males (23.2 × 18.7 mm, 20.4 × 16.7 mm, 14.2 × 11.9 mm), 3 females (largest 19.9 × 16.3 mm, 19.9 × 16.1 mm, 16.7 × 13.5 mm) ( ZRC 2012.0062 View Materials ), station CI-14, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 27 Jan.2010 GoogleMaps   2 males, 1 female ( ZRC 2012.0063 View Materials ), station CI-17, Runaway Cave , Waterfall Road, 10°25.386'S, 105°42.063'E, coll. Xmas Island Expedition 2010, 28 Jan.2010 GoogleMaps   1 male (16.0 × 13.4 mm), 1 ovigerous female (17.3 × 14.3 mm) ( ZRC 2012.0064 View Materials ), station CI-18, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2010, 28 Jan.2010 GoogleMaps   1 male (15.4 × 12.9 mm) ( ZRC 2011.0065 View Materials ), station CI-26, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2011, 25 Mar.2011 GoogleMaps   1 male (17.3 × 14.4 mm) ( QM-W29116), station CI-29, Whip Cave , Waterfall Road, 10°25.377'S, 105°42.081'E, coll. Xmas Island Expedition 2011, 26 Mar.2011 GoogleMaps   1 male ( QM-W29214), station CI-30, Freshwater Cave , near The Blowholes, 10.51325°S, 105.62421°E, coll. Xmas Island Expedition 2010, 02 Feb.2010 GoogleMaps   1 male (17.6 × 14.4 mm) ( QM-W29215), station CI-31, Whip sinus, low transverse ridge of granules just behind true frontal margin defining a deflexed narrow anterior median strip ( Fig. 5B View Fig ); infraorbital margins incomplete, median lobe low, convex, coarsely granulate, separated from exorbital tooth by deep sinus; distinct row of rounded granules below infraorbital margin on suborbital region, extending to subbranchial region ( Fig. 5B View Fig ). Antennal segments entering orbital hiatus. Antennules broad; interantennular septum broad. Eyes well-developed, cornea pigmented. Epistome ( Fig. 5B View Fig ) relatively narrow, posterior margin with 2 lateral clefts, median part broadly triangular, margin coarsely granulate. Third maxilliped ( Fig. 5B View Fig ) with broad, stout exopod, exopod 0.9 times as narrow as ischium, flagellum well developed; ischium stout (length to width ratio ca. 2.0, measured along outer edge), smooth, 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; fingers as long as palm; base of fingers and adjacent areas with long, dense setae ( Fig. 6A, B View Fig ), longer on smaller adult males, without distinct pulvinus. Merus trihedral, external and posterior margins with low granules, inner anterior margin armed with row of 8–10 large rounded granules. Carpus rounded, smooth, inner distal angle with low, obtuse tooth. Female chelae similar to those of male but smaller, non-setose.

Ambulatory legs somewhat dorsoventrally flattened, all segments long, slender; second ambulatory leg slightly longer than third; surface smooth. Meri each with long patch of fine setae over upper third adjacent to carapace, relatively sparse on last leg; 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 4.0), 3P long, slender (length to width ratio 3.8), 3D very long, slender (length to width ratio 7.5); 4M long, slender (length to width ratio 3.7), 4P long (length to width ratio 2.6), 4D long, slender (length to width ratio 5.5).

Male abdomen narrowly triangular ( Fig. 9A View Fig ); 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 moderately sinuous, lateral margins convergent; sixth abdominal somite rectangular 1.9 times wider than long, lateral margins weakly convex distally, proximal margin straight; telson slightly longer than wide (ca. 1.1 times), lateral margins subparallel, broadly rounded distally. Female abdomen very broad, covering most of thoracic sternum ( Fig. 9B View Fig ).

Male thoracic sternum ( Fig. 9A View Fig ) 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 slightly convex antero-medially; 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 View Fig A–C) slender, weakly curving outwards, reaching to or slightly beyond anterior margin of sternite 5; terminal lobe elongate; genital opening lateral to base of apical corneous section; subterminal lobe pectinated, elongate, densely setose. G2 short, small ( Fig. 11D View Fig ). Vulva raised, convex, oval.

Colour. — In life, the colour was an orangish-yellow to pale yellowish-white, with branchial regions paler; setae on the chela were dark brown ( Fig. 1 View Fig ).

Etymology. — Named for Max and Beverley Orchard. As Head Ranger on Christmas Island for 18 years, and continuing on as Project Officer, Max, with the wonderful support of his wife Bev, have worked tirelessly for the conservation of the biota of Christmas Island. In particular Max, has spearheaded the control of the Yellow Crazy Ant ( Anoplolepis gracilipes   ), which has had a devastating effect on the crab populations of the island. Without people who care, like Max and Bev, the world would be a much poorer place!

Remarks. — Orcovita orchardorum   , new species, most resembles O. holthuisi   from Coron Island, the Philippines, and O. miruku   from the Ryukyus, Japan.

In O. holthuisi   , the anterolateral teeth are both acute (cf. N. K. Ng & Ng, 2009: Figs. 1 View Fig , 3A View Fig ), whereas in O. orchardorum   , new species, the second tooth is more in the form of a broad lobe without a deep notch ( Figs. 1 View Fig , 4 View Fig , 5A View Fig ); the sixth male abdominal somite about 2.3 times wider than long (cf. N. K. Ng & Ng, 2009: Fig. 3K View Fig ) versus 1.9 times in O. orchardorum   , new species ( Fig. 9A View Fig ); and the male telson 1.5 times the length of the sixth abdominal somite (cf. N. K. Ng & Ng, 2009: Fig. 3K View Fig ) versus ca. 1.1 times in O. orchardorum   , new species ( Figs. 9A View Fig ). Their leg proportions (P4 & P5) also differ, as summarised in Table 2.

In O. miruku   , the anterolateral teeth are similarly broadly rounded but both are clearly defined and similar in prominence (cf. Naruse & Tamura, 2006: Figs. 1 View Fig , 2a View Fig ), whereas in O. orchardorum   , new species, the first anterolateral tooth is deeply notched and prominently projecting, while the second is smaller and less strongly defined by a deep notch ( Figs. 1 View Fig , 4 View Fig , 5A View Fig ). Also in O. miruku   , the male telson is slightly longer, 1.2 times length of sixth abdominal somite (cf. Naruse & Tamura, 2006: Fig. 2g View Fig ) versus 1.1 times in O. orchardorum   , new species ( Fig. 9A View Fig ).

Orcovita orchardorum   , new species, can also be easily separated from its fellow islander, O. hicksi   , new species, by having two epibranchial teeth instead of only one ( Figs. 1 View Fig , 4 View Fig , 5A View Fig versus Figs. 2A View Fig , 3 View Fig , 7 View Fig , 8A View Fig ); relatively prominent postfrontal lobes compared with post-frontal lobes obsolete ( Figs. 1 View Fig , 4 View Fig , 5A View Fig versus Figs. 2A View Fig , 3 View Fig , 7 View Fig , 8A View Fig ); relatively shorter, stockier legs versus longer more slender legs ( Figs. 1 View Fig , 4 View Fig versus Figs. Figs. 2A View Fig , 3 View Fig , 7 View Fig ); and a distinct thick patch of long setae at the base of the gape of the male chela that extends onto the fingers, a feature that is lacking in O. hicksi   , new species ( Fig. 6A, 6B View Fig versus Figs. 2C View Fig , 6C, 6D View Fig ). In addition, the deflexed portion of the front above the interantennular septum is a narrow strip in O. orchardorum   , new species, but is relatively wider in O. hicksi   , new species ( Fig. 5B View Fig versus Figs. 2B View Fig , 8B View Fig ). Finally, the sixth abdominal somite is proportionately narrower in O. orchardorum   , new species (1.9 times wider than long versus 2.2 times) ( Fig. 9A View Fig versus Fig. 9C View Fig ).

Habitat. — Orcovita orchardorum   , new species, and O. hicksi   , new species, are relatively abundant in Whip and Runaway Caves that are about 50 m apart from each other above ground and almost certainly have a subterranean connection. Both caves are tidally and freshwater influenced brackish anchialine habitats. Orcovita hicksi   , new species, has also been collected 19 th Hole Cave, which is only a few kilometres away. Both species were found from Freshwater Cave, near The Blowholes a site much further south. As these animals clearly have a marine dispersal phase, this is not surprising. We only managed to collect one ovigerous female (17.3 × 14.3 mm, ZRC) from Whip Cave but we could not get the eggs to hatch. The eggs are small and numerous, and typical of varunids.

Both new species of Orcovita   were collected with other decapods including the alpheid shrimp Metabetaeus minutus ( Whitelegge, 1897)   (see Anker, 2010), a possible new species of hippolytid shrimp, Parahippolyte sp., a new species of Macrobrachium   ( Palaemonidae   ), and an atyid shrimp Antecaridina   (?) lauensis ( Edmondson, 1935).

Besides these, numerous other aquatic species have already been previously reported within the same wider cave systems including: an unidentified Scyllidae   sp. ( Polychaeta  ); Nerilla   sp. (Archiannelida: Nerillidae   ); Microceratina martensi   ( Ostracoda  : Cytheruridae   ); Danielopolina baltanasi   ( Thaumatocyprididae   : Halocyprida   ) (Humphreys & Danielopol, 2006; Humphreys et al., 2009); Nitocrella   / Nitokra   complex ( Harpacticoida   : Ameiridae   ); Bryocyclops muscicola (Menzel)   ( Cyclopoida   : Cyclopinidae   ); a new copepod genus ( Calanoida   : Arietellidae   ); Leucothoe   sp. ( Amphipoda   : Leucothoidae   ); Macrobrachium lar (Fabricius)   ( Decapoda   : Palaemonidae   ); Gobioidae indet. (Pisces: Perciformes   ); unidentified Eleotridae   (Pisces: Perciformes   ) (see Humphreys & Eberhard, 2001; Namiotko et al., 2004); Eleotris   (?) fusca ( Eleotridae   ) (Humphreys & Eberhard, 2001; Namiotko et al., 2004). Three species of eels ( Anguilla bicolor   , Anguillidae   ), Echidna   sp. ( Muraenidae   ), and an unidentified muraenesocid were also present in Whip and Runaway Caves (H. H. Tan, pers. comm.).

In general, according to Humphreys & Eberhard (2001), the cave waters are all well oxygenated (dissolved oxygen>73% saturated) and the pH (7.65±0.41, N =13), with the marine caves having salinities ranging from 0.39–16.5 g L– 1 TDS (sea water c. 36 g L– 1 TDS). Specific physico-chemical measurements for Runaway Cave, and the nearby 19 th Hole Cave, are presented in Table 1. Runaway Cave is brackish with salinities ranging from about 9–18 ppt. No measurements deeper than 2 m were taken so it is not known if deeper waters become suboxic as reported for many other anchialine systems (see Sket, 1996; Humphreys, 1999; Iliffe, 2000).