Alainodaeus filipinus, Mendoza, Jose Christopher E. & Ng, Peter K. L., 2008

Mendoza, Jose Christopher E. & Ng, Peter K. L., 2008, A new species of Alainodaeus Davie, 1993 (Crustacea: Decapoda: Brachyura: Xanthidae) from Balicasag Island, Philippines, with a key to the genus, Zootaxa 1897, pp. 53-63 : 55-60

Alainodaeus filipinus n. sp.

( Figs. 1 –4)

Material examined. Holotype: ď (16.5 × 12.0 mm) ( NMCR 27161), Philippines, Balicasag Island, 100–500 m, from fishermen with tangle nets, coll. P. K. L. Ng, 2 March 2004. Paratypes: 1 ď (8.8 × 6.4 mm) ( ZRC 2008.0895), from fishermen with tangle nets, 100–500 m, Balicasag Island, coll. P. K. L. Ng, December 2000; 1 ď, with bopyrid isopod in branchial chamber (21.8 × 15.0 mm) ( ZRC 2008.0896), tangle net, 100–300 m, Maribohoc Bay, Bohol, coll. J. Arbasto, between November 2003 to April 2004; 1 Ψ (11.2 × 8.2 mm) ( ZRC 2008.0897), from fishermen with tangle nets, 100–500 m, Balicasag Island, coll. P. K. L. Ng, March 2004; 1 Ψ (11.1 × 8.0 mm) ( ZRC 2008.0898), from fishermen with tangle nets, 50–500 m, Balicasag Island, coll. Panglao 2004 Marine Biodiversity Project, 14 June 2004; 1 ď (15.5 × 10.8 mm), 1 Ψ (13.0 × 8.9 mm) ( ZRC 2008.0899), Philippines, stn DW2402, off Balicasag Island, 101–118 m, 9°30.8’N, 123°41.5’E, coll. M/V DA-BFAR, Panglao 2005 Cruise, 31 May 2005.

Comparative material. Alainodaeus akiaki Davie, 1993 , holotype ď (29.2 × 19.4 mm) (MNHN- B22243), caught in pots, 230-240 m, Rurutu, Austral Islands, coll. F.R.V. Marara, J. Poupin , 10 March 1989. Alainodaeus alis, Davie, 1997 , holotype ď (8.1 × 5.9 mm) (MNHN-B22809), stn DW 73, 573 m, New Caledonia, coll. CHALCAL 2, 29 October 1986. Alainodaeus nuku Davie, 1997 , holotype ď (8.9 × 6.1 mm) (MNHN-B22778), stn D 83, 140 m, Nuku Hiva, Marquesas Islands, coll. J. Poupin, 25 January 1991. Alainodaeus rimatara Davie, 1993 , holotype ď (22.4 × 15.3 mm) (MNHN-B22244), trapped, 250-300 m, Akiaki , Tuamotu Archipelago coll. F.R.V. Marara, J. Poupin , 10 June 1989.

Diagnosis. Carapace ( Fig. 2 A, B) about 1.4 times broader than long, regions moderately defined; 2M faintly, partially divided longitudinally, 3M prominent, 4M indistinct; grooves bordering 3M, posterior 2M, and 6L deep and smooth; dorsal regions of carapace granulose, with anterior half bearing larger granules; suborbital, subhepatic and pterygostomial regions similarly granulose. Front about 0.3 times carapace width, bilobed, slightly deflexed ventrally; frontal margin sinuous, with a narrow, smooth strip just posterior to it, immediately followed by rows of granules; lobes separated by shallow V-shaped cleft, continuous with a median fissure on frontal region. Supraorbital margin granulose, relatively short, no obvious external orbital tooth, not clearly meeting anterolateral margin. Orbits relatively small, width about 0.1 times carapace width. Anterolateral margin convex, with 4 teeth - 1st and 4th feeble, 2nd and 3rd more distinct, with 3rd tooth at the point of maximum carapace width; anterior-most part not clearly meeting orbital margin. Posterolateral margin more-or-less straight, convergent posteriorly. Central portion of posterior carapace margin, straight, with distinct row of granules anterior to it.

Eyes with short eyestalks, distal edge with cornea lined with small, tooth-like granules; corneas well developed ( Fig. 2 D). Antennules ( Figs. 2 D, 3A) folding transversely. Basal antennal segment long, granulose, subrectangular, occupying entire space between antennular fossa and internal orbital angle, filling orbital hiatus; long flagellum arising from distal margin, reaching well beyond outer edge of orbit. Posterior margin of epistome ( Figs. 2 D, 3A) slightly sinuous and sweeping slightly outward, with a shallow median notch continuing as a median fissure which widens anteriorly; also with 1 lateral notch on either half. Posterior portion of endostome (Fig. 3A) with oblique ridge on either side; mesial edge of endopod of 1st maxilliped not reaching beyond ridges. Outer surface of 3rd maxillipeds (Fig. 4B) granulose. Merus subquadrate, with slight extension of anteroexternal angle, median length about half that of ischium, with 2 shallow depressions on either side of a low, submedian, granular ridge; margins more-or less straight, lined with small granules. Ischium subrectangular, inner margin with short, stiff setae; with deep, longitudinal sub-median groove; separated from basis by feeble suture. Exopod granulose, tapering toward distal end which just reaches anterior edge of merus, flagellum long.

Surface of male thoracic sternum ( Figs. 2 C, 4A) sparsely setose, with small granules, anterior region elongate. Sternites 1 and 2 completely fused into triangular plate, separated from sternite 3 by distinct transverse suture. Sternites 3 and 4 partially fused, with a lateral notch on either side which is replaced by a distinct groove medially; sternite 4 with deep, median, longitudinal furrow. Male abdominal cavity deep, sternal condyle slightly off-center on sternite 5, slightly nearer to suture with sternite 6, abdomen almost reaching to imaginary line joining posterior edges of cheliped coxae.

FIGURE 3. Alainodaeus filipinus n. sp., holotype ♂ (16.5 × 12.0 mm) (NMCR 27161), Balicasag Island, Philippines. A, fronto-ventral view, showing antennae, antennules, epistome, endostome, mouthparts; B, right 3rd and 4th ambulatory legs, dorsal view; C, major chela, external view; D, minor chela, external view.

Chelipeds ( Figs. 2 A, 3C, D) distinctly unequal, right chela larger and stouter, left chela more slender. Merus granulose on external surface, slightly longer than carpus, with distinct row of granules on convex dorsal margin. Carpus short, dorsal and ventral surface granulose, inner margin with 2 spinose teeth. In both chelae, external surface of palm granulose, upper margin slightly convex, with proximal end terminating as a sphaeroidal projection, central portion of lower margin more prominently convex; inner surface relatively smoother, except for 3 or 4 large, conical, inwardly projecting granules on upper margin and a feeble, median row of granules. Major chela with fingers stout, distinctly shorter than palm, with pointed, incurving tips, and pigmented throughout most of their length; fixed finger slightly deflexed with submarginal groove on external surface, cutting surface with 3 large teeth medially; dactylus slightly curved, with 2 grooves on external surface, cutting margin with large subproximal tooth, with a depression near point of articulation with palm to receive a rounded projection on palm distal margin. Minor chela with fingers slender, about as long as palm; no large, subproximal tooth on dactylus.

Ambulatory legs ( Figs. 2 A, 3B) relatively long, slender, third leg longest, coxa-to-dactylus length about 1.3 times carapace width. Merus subrectangular, subcylindrical in cross-section; anterior edges, with 2 parallel rows of low, conical granules; dorsal surface in fourth ambulatory leg more granulose than rest. Carpus narrow proximally, widening distally, dorsal surface with rows of conical or rounded granules, with more closely packed and conical granules on anterior half. Propodus subrectangular, with larger conical granules on edges and dorsal surface and with sparse, stiff setae on posterior edge. Dactylus straight, anterior and posterior edges covered with short, stiff setae; terminates distally in curved chitinous claw.

External surface of male abdomen and telson (Fig. 4C) granulose and with sparse, fine setae. Somite 1 longer at lateral edges and forming a concave distal margin; larger granules on lateral portions. Somite 2 subtrapezoidal, proximal and lateral margins convex, distal margin concave; with larger granules on lateral portions. Somites 3–5 immovably fused, vestigial sutures seen as shallow grooves; external surface with finer, lower granules; lateral margins markedly concave. Somite 6 rectangular, about 1.9 times wider than long, central region raised, lateral margins slightly concave. Telson subtriangular with rounded tip, about 1.7 times wider than long, and about as long as penultimate somite.

G1 (Fig. 4D, E) moderate in length, stout, curving laterally, tapering distally into 2 unequal lobes, external lobe small, narrow, internal lobe large, spatulate; subterminal setae absent; distal two-thirds covered with long and short spines, mostly found on internal surface, longest spines found in a row on mesial margin; lateral margin with distinct keel in central region; basal region wide, with a few plumose setae. G2 (Fig. 4F) about half length of G1, curving mesially, tip recurved.

Coloration. The dorsal surface of the carapace ( Fig. 1 ) has a yellowish white background, with small, isolated patches of white on the branchial, cardiac and intestinal regions. The granules found on the anterior half of the carapace are mostly orange and tipped with dark, reddish-orange. The chelipeds have a similar color pattern, with the carpus and palm also invested with the reddish orange-tipped granules; the fingers of the chelae are colored brown throughout their length, but brown color does not extend to the palm. The ambulatory legs are alternately colored orange and white along their entire length, particularly the meri, giving them a banded appearance.

Etymology. This species is named after the Philippines, using its older Spanish name, Las Islas Filipinas. Used as a noun in apposition.

Remarks. Alainodaeus filipinus n. sp. is similar to congeners in the following characters: 1) the general outline of the carapace; 2) the four, relatively low anterolateral teeth (or lobes), with the first tooth being much reduced; 3) the non-protrusive, deflexed, and bilobed front; 4) the moderately defined carapace regions; 5) the distinct, oblique ridges on the lateral regions of the endostome; 6) the lateral notches and shallow transverse furrow on the anterior sternum indicating the partial fusion of the 3rd and 4th sternites; 7) the presence of a deep, median, longitudinal furrow on the 4th sternite; 8) the short and wide male abdomen; 9) the relatively long and slender ambulatory legs; 10) the presence of a flange/crest on the lateral margin of the G1; and 11) the absence of terminal or subterminal setae on the G1 (cf. Davie 1993, 1997). The live colouration of some species of Alainodaeus also bears some similarities, particularly in the orange-and-white banding pattern seen in the ambulatory legs, as well as the orange “dotting” or “clouding” on the dorsal surface of the carapace (cf. Poupin 1996).

FIGURE 4. Alainodaeus filipinus n. sp., holotype ♂ (16.5 × 12.0 mm) (NMCR 27161), Balicasag Island, Philippines. A, left 3rd maxilliped, external view; B, anterior thoracic sternum (sternites 1-2, 3, 4), ventral view; C, pleon (abdominal somites 1-6, telson), external view; D, G1, external view; E, G1, internal view; F, G2, external view. Scale bars: A-C = 2.0 mm, D-F = 0.5 mm.

Alainodaeus filipinus n. sp. most closely resembles A. alis , A. nuku and A. rimatara in the form of the carapace and pereopods. However, it can be distinguished from A. alis (cf. Davie 1997: 348, fig. 4) by the presence of well-defined teeth on the anterolateral margin of the carapace (vs. irregularly serrated, divided into lobes in A. alis ) ( Fig. 2 A, B); the presence of two spines on the inner surface of the cheliped carpus (vs. only one spine in A. alis ) ( Figs. 1 , 2 A, B); the relatively smoother anterior margin of the merus of the ambulatory legs lined, at most, with small granules (vs. serrated in A. alis ) (Fig. 3B); and the structure of the G1, which is longer and more slender (vs. shorter and stouter in A. alis ), and where the terminal end has a major and minor lobe (vs. terminal end fluted and without lobes in A. alis ), and where the lateral crest is moderately produced (vs. strongly produced in A. alis ) (Figs. 4D, E). Alainodaeus filipinus can also be separated from A. rimatara (cf. Davie 1993: 519, fig. 6, pl. 6) and A. nuku (cf. Davie 1997: 350, fig. 5) by the low and broad teeth on the carapace anterolateral margin (vs. more pronounced, acute and forward-curving in A. rimatara ) ( Fig. 2 B); the setose and straight mesial margin of the ischium of the 3rd maxilliped (vs. glabrous, with produced posteromesial border in A. rimatara ; less setose in A. nuku ) (Fig. 4B); the presence of granules on the entire external surface of the palm of the chela (vs. limited to dorsal half only in A. rimatara and A. nuku ) (Fig. 3C, D); the relatively smoother anterior margin of the merus of the ambulatory legs (vs. more serrated or spinose in A. rimatara and A. nuku ); the longer and more slender G1 (vs. shorter and stouter, with a concavity in the lower half of the mesial side in A. nuku ), and the broader and spatulate major lobe and the small, but distinct, minor lobe on the terminal end of the G1 (vs. narrow major lobe and indistinct minor lobe in A. rimatara ) (Fig. 4E, F).

Alainodaeus filipinus n. sp. is similar to A. akiaki in the form of the G1 (cf. Davie 1997: 517, fig. 5, pl. 5). However, A. filipinus n. sp. is easily distinguished from it by the relatively narrower carapace, CW/CL ratio about 1.4 (vs. broader carapace, CW/CL ratio 1.5–1.6, in A. akiaki ) ( Fig. 2 A, B); the presence of a narrow agranular strip near the frontal margin (vs. absent in A. akiaki ) ( Fig. 2 D); the less produced anterolateral angle of the merus of the 3rd maxilliped (vs. more produced in A. akiaki ) (Fig. 4B); the absence of median and ventral rows of spinules on the inner face of the palm of the cheliped (vs. present in A. akiaki ); the relatively smoother anterior margin of the meri of the ambulatory legs, which are lined with very low granules (vs. serrated in A. akiaki , lined with large spinules) (Fig. 3B); and the relatively shorter and broader telson on the male (vs. longer and narrower in A. akiaki ) (Fig. 4C).

Figures

FIGURE 1. Live colour, Alainodaeus filipinus n. sp., paratype ♂ (15.5 × 10.8 mm) (ZRC 2008.0899), Balicasag Island, Philippines.

FIGURE 2. Alainodaeus filipinus n. sp., holotype ♂ (16.5 × 12.0 mm) (NMCR 27161), Balicasag Island, Philippines. A, habitus, dorsal view; B, carapace, dorsal view; C, ventral view; D, frontal view.