Microgoneplax prion, 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 : 731-734

Microgoneplax prion n. sp.

( Figs 45 ; 46 )

TYPE MATERIAL. — MUSORSTOM 5, stn DW 280, ♂ holotype, cl 3.9 mm, cw 7.3 mm ( MNHN-B 29318). Paratypes: one male and six female specimens from the Chesterfield Is and New Caledonia as listed under Material examined.

TYPE LOCALITY. — Chesterfield Islands, 24°09.99’S, 159°35.75’E, 270 m.

MATERIAL EXAMINED. — Chesterfield Islands. MUS- ORSTOM 5, stn DW 280, 24°09.99’S, 159°35.75’E, 270 m, 10.X.1986, 1 ♂ holotype cl 3.9 mm, cw 7.3 mm ( MNHN-B 29318). — Stn DW 281, 24°10.54’S, 159°34.32’E, 272 m, 10.X.1986, 1 ♀ paratype cl 3.6 mm ( MNHN-B 29320). — Stn DW 299, 22°47.70’S, 159°23.70’E, 370-390 m, 11.X.1986, 1 pre-adult ♀ parasitised by bopyrid cl 4.6 mm, cw 8.9 mm ( MNHN-B 29321). — Stn DW 334, 20°06.27’S, 158°47.62’E, 315-320 m, 15.X.1986, 1 ♀ paratype cl 4.8 mm, cw 9.1 mm ( MNHN-B 29319). — Stn DC 376, 19°51.10’S, 158°29.80’E, 280 m, 20.X.1986, 1 ovig. ♀ paratype cl 6.4 mm, cw 11.7 mm ( MNHN-B 29315).

EBISCO, stn DW 2509, 24°08’S, 159°35’E, 265 m, 8.X.2005, 1 ♂ cl 4.6 mm ( MNHN-B 30460).

New Caledonia. BATHUS 4, stn CP 901, 19°02.72’S, 163°15.39’E, 297 m, 4.VIII.1994, 1 ♂ paratype cl 3.7 mm, cw 6.6 mm ; 2 ♀♀ paratypes (cl 4.0 mm, cw 7.8 mm; cl 3.3 mm, cw 6.5 mm) ( MNHN-B 29339 ). ETYMOLOGY. — From prion , noun in apposition, Greek for “saw”, in reference to the thin, denticulated, saw-like G1 characteristic of the species .

DISTRIBUTION. — Chesterfield Is and New Caledonia. Depth: 265- 297 m.

DESCRIPTION

Carapace ( Figs 45A ; 46 ) transversely rectangular, much wider than long (1.9 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, granular, each with large, wide, rectangular inner tooth not visible dorsally. Relatively short, nearly triangular 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 45A ; 46 ) long (equal to front width), cornea elongated, spherical distal margin, not reniform.

Chelipeds (P1) ( Fig. 46 ) unequal in both sexes; fingers slender, dactylus strongly curved in males, slightly curved in females, shovel-like, slightly shorter than propodus (heavier chela of male holotype much shorter than propodus), with blunt teeth; no dark colour on fingers; inner (ventral) margin of propodus with large, round tubercles in holotype, small tubercles in remaining specimens. Broad tooth on inner (ventral), proximal margin of carpus; outer (dorsal) margin of merus with low, tooth-like tubercles (larger in male holotype), long simple setae. Ambulatory legs (P2-P5) ( Fig. 46 ) long, slender, unarmed, varying number of long simple setae; dactyli long, slender,

Revision of Goneplacinae ( Crustacea, Brachyura)

each with 2 carinae along each side; length of P5 merus 0.8 cl.

Male abdomen narrowly triangular, with 6 freelymovable 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. 45B ) long, slender, thin, slightly wider basal part, sinuous distal part with denticles along inner margin; slender, pointed tip with 2 minute processes. G2 ( Fig. 45C ) slender, short, less than half G1 length; slightly curved, thick flagellum about same length of proximal part (peduncle), much expanded tip with terminal spinule.

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 small portion of thoracic sternite 8 visible. Vulva of mature females relatively large, oblong, extending from edge of suture 5/6 to median portion of thoracic sternite 6, covered by small, rounded vulvar cover on inner margin plus a small projection on pos- terior margin; thin vulvar cover on enlarged vulva of large females.

COLOUR

The holotype, which was photographed soon after collection ( Fig. 46 ), was transparent, with a few irregular orange-yellow marking on the carapace and chelipeds.

REMARKS

The G1 of the new species is similar to that of Microgoneplax elegans n. comb. (see Chen 1998: fig. 14-7, as Ommatocarcinus elegans ). In both species the G1 is slender along the entire length without a broad median portion. It is nevertheless straighter and has larger denticles in the new species. A more diagnostic difference between the two species is the much wider male abdomen of M. elegans n. comb. ( Chen 1998: fig. 14-6). The outer orbital tooth of M. prion n. sp. is relatively short and nearly triangular ( Figs 45A ; 46 ), not as slender as in M. elegans n. comb. and its congeners.

An unusually large female (cl 6.4 mm, cw 11.7 mm; MNHN-B 29315) agreed with all of the characters of the species except the vulva. It was large, reminiscent of that of Carcinoplax in its relative size. The vulva was oblong, with square anterior margins, slightly pointed posterior margins, and extending from 5/6 suture to 6/7 suture. Both sutures were slightly displaced, curving around the margins of the vulva. The vulva was covered by a thin, sclerified vulvar cover.

Figures

FIG. 45. — Microgoneplax prion n. sp., ♂ holotype, cl 3.9 mm, cw 7.3 mm, Chesterfield Is, MUSORSTOM 5, stn DW 280 (MNHN-B 29318): A, dorsal surface of the carapace; B, left G1, ventral view; C, left G2, ventral view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 46. — Microgoneplax prion n. sp., ♂ holotype, cl 3.9 mm, cw 7.3 mm, Chesterfield Is, MUSORSTOM 5, stn DW 280 (MNHN-B 29318) (photo by P. Laboute, IRD, Nouméa).