Microgoneplax caenis, Castro, 2007

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 726-728

Microgoneplax caenis n. sp.

( Figs 41 ; 42 )

TYPE MATERIAL. — PANGLAO 2004, stn T27, ♂ holotype, cl 4.2 mm, cw 7.1 mm ( NMCR 27014). Paratypes: seven other males, four females, and one pre-adult specimen from the type locality as listed under Material examined.

TYPE LOCALITY. — Philippine Islands, between Panglao and Pamilacan islands, 09°33.4’N, 123°51.0’E, 106- 137 m.

MATERIAL EXAMINED. — Philippine Islands. Bohol, Balicasag I., off Panglao I., PANGLAO 2004, stn T27, between Panglao and Pamilacan islands, 09°33.4’N, 123°51.0’E, 106-137 m, fine sand and mud, 25.VI.2004, 1 ♂ holotype cl 4.2 mm, cw 7.1 mm ( NMCR 27014 ) ; 3 ♂♂ paratypes (cl 3.4 mm, cw 5.8 mm; cl 2.9 mm, cw 4.7 mm; cl 2.3 mm, cw 3.6 mm), 1 ♂ paratype feminized by two Sacculina parasites (cl 3.2 mm, cw 5.5 mm), 1 ♀ paratype (cl 3.4 mm, cw 6.3 mm), 2 pre-adult ♀♀ paratypes (cl 2.8 mm, cw 4.7 mm; cl 2.6 mm, cw 4.3 mm), 1 pre-adult paratype (cl 1.6 mm, cw 3.3 mm) ( ZRC 2004.0788 ) ; 3 ♂♂ paratypes (cl 3.6 mm, cw 6.6 mm; cl 2.7 mm, cw 4.9 mm; cl 2.2 mm), 1 pre-adult ♀ paratype (cl 2.6 mm, cw 4.3 mm) ( MNHN-B 30062 ). — Stn T 9, Panglao I. off San Isidro, 09°33.5’- 09°33.9’N, 123°49.5’- 123°50.5’E, 97-120 m, fine sand with seagrass, 14.V.2004, 1 ♂ paratype ( ZRC 2006.0171 ) .

ETYMOLOGY. — From kaenis, noun in apposition, Greek for “knife,” in reference to the knife-like G1 characteristic of the species.

DISTRIBUTION. — Known only from the Philippine Is. Depth: 106- 137 m.

Revision of Goneplacinae ( Crustacea, Brachyura)

DESCRIPTION

Carapace ( Figs 41A ; 42 ) transversely rectangular, much wider than long (1.7 as wide as long in holotype). Carapace convex, without clear indication of regions. Front slightly convex, almost straight. Notch between front, inner edge of supraorbital border. Supraorbital borders broad, conspicuously sinuous, finely granular, with long simple setae. Suborbital borders conspicuously sinuous, with large granules, each with large, wide, rectangular inner tooth not visible dorsally. Long, slender, acute tooth on outer orbital angle. Lateral borders beyond outer orbital teeth slightly convex, no anterolateral teeth.

Subhepatic, pterygostomial regions, with low, round tubercles.

Eye peduncles ( Figs 41A ; 42 ) long (0.7 front width), cornea elongated, spherical distal margin, not reniform.

Chelipeds (P1) ( Fig. 42 ) slightly unequal in males, nearly equal in females; fingers slender, slightly curved, shovel-like, slightly shorter than propodus, with blunt teeth, dactylus conspicuously curved in heavier chelipeds of large males; no dark colour on fingers; inner (ventral) margin of propodus with large, round tubercles in large males. Broad tooth on inner (ventral), proximal margin of carpus; outer (dorsal) margin of merus with low, toothlike tubercles, long simple setae. Ambulatory legs (P2-P5) ( Fig. 42 ) long, slender, unarmed, varying number of long simple setae; dactyli long, slender, each with 2 carinae along each side; length of P5 merus 0.7 cl.

Male abdomen ( Fig. 41B ) narrowly triangular, with 6 freely-movable somites plus telson; telson longer than wide. Somite 3 covers most space between P5 coxae; somite 2 only slightly narrower than somite 3, leaving large portion of thoracic sternite 8 visible. G1 ( Fig. 41C ) long, slender, slightly wider basal part, straight distal part; median portion bent, thicker, with rounded inner margin, large denticles along inner, outer margins; slender, pointed tip. G2 ( Fig. 41D ) slender, short, less than half G1 length; slightly curved, thick flagellum about same length of proximal part (peduncle), expanded tip with 2 large terminal spinules.

Female abdomen wide, outer margin of thoracic sternites visible. Telson much wider than long. Somite 3 covers space between P5 coxae, somites 1, 2 narrower than somite 3, leaving large portion of thoracic sternite 8 visible. Vulva of mature female paratype small, extending from edge of suture 5/6 to median portion of thoracic sternite 6, covered by large, flat vulvar cover leaving semi-circular inner opening.

REMARKS

The relatively abundant material of specimens of varying sizes and belonging to both sexes, all collected from one station in the Philippine Is, allows the description of the new species. The species has not yet been collected elsewhere.

Diagnostic of the species is its characteristic G1. It has a slender and pointed tip, and the median portion is bent, thicker than the tip, and with a row of large denticles along the inner and outer margins ( Fig. 41C ). The G2 is also diagnostic, having an expanded tip with two large terminal spinules ( Fig. 41D ). The male abdomen is slender as in all congeners except M. elegans ( Chen, 1998) n. comb.

Figures

FIG. 41. — Microgoneplax caenis n. sp., ♂ holotype, cl 4.2 mm, cw 7.1 mm, between Panglao and Pamilacan islands, Philippine Is, PANGLAO 2004, stn T27 (NMCR 27014):A, dorsal surface of the carapace; B, abdomen;C, right G1, ventral view; D, right G2,ventral view. Scale bars: A, 5 mm; B, 2 mm; C, D, 1 mm.

FIG. 42. — Microgoneplax caenis n. sp., ♂ holotype, cl 4.2 mm, cw 7.1 mm, between Panglao and Pamilacan islands, Philippine Is, PANGLAO 2004, stn T27 (NMCR 27014).