Ethusina crenulata, Castro, 2005

Castro, Peter, 2005, Crabs of the subfamily Ethusinae Guinot, 1977 (Crustacea, Decapoda, Brachyura, Dorippidae) of the Indo-West Pacific region, Zoosystema 27 (3), pp. 499-600 : 579-580

Ethusina crenulata n. sp.

( Figs 27 ; 28 )

TYPE MATERIAL. — Holotype: cl 9. 8 mm, cw 9.6 mm, MUSORSTOM 9, stn 1282 ( MNHN-B

28717); paratypes: cl 11.1 mm, cw 10.6 mm, cl 10.1 mm, cw 10.0 mm, MUSORSTOM 9, stn CP 1276 ( MNHN-B 28718); cl 10.2 mm, cw 9.8 mm, cl 10.9 mm, cw 10.9 mm, same station ( MNHN-B 28720); cl 10.4 mm, cw 10.1 mm ,, cl 10.8 mm, cw 10.4 mm, same station ( USNM 1024422).

TYPE LOCALITY. — French Polynesia, Marquesas Islands, off Eiao island, 07°52’S, 140°31’W, 416- 460 m.

MATERIAL EXAMINED. — French Polynesia. Marquesas Islands, MUSORSTOM 9, stn CP 1270, 07°56’S, 140°43’W, 497-508 m, 4.IX.1997, 1 ( MNHN-B 28722). — Stn CP 1272, 07°55’S, 140°44’W, 660-680 m, 4.IX.1997, 1 ( MNHN-B 28723). — Stn DW 1275, 07°53’S, 140°38’W, 627 m, 5.IX.1997, 1 ( MNHN-B 28721). — Stn CP 1276, 07°52’S, 140°37’W, 800-805 m, 5.IX.1997, 8, 2 parasitized by Sacculina sp. , 5, 11 parasitized by Sacculina sp. ( MNHN- B 28724), 1 paratype, 1 paratype ( MNHN-B 28718), 1 paratype, 1 paratype ( MNHN-B 28720), 1 paratype, 1 paratype ( USNM 0000). — Stn DW 1277, 07°52’S, 140°39’W, 1000-1100 m, 5.IX.1997, 2 ( MNHN-B 28726). — Stn 1278, 07°52’S, 140°39’W, 1000 m, 5.IX.1997, 2, 3, 2 parasitized by Sacculina sp. ( MNHN-B 28719). — Stn 1282, 07°52’S, 140°31’W, 416- 460 m, 7.IX.1997, 1 holotype ( MNHN-B 28717). ETYMOLOGY. — From crenula, diminutive of crena (Latin for notch or fissure), in reference to the small vertical fissure at the dorsal lower margin of each of the orbital sinuses in this species.

DISTRIBUTION. — Known only from the Marquesas Islands, French Polynesia. Depth: 416-1100 m ( Fig. 34 ).

SIZE. — Maximum size: 11.1 cl mm, cw 10.6 mm (MNHN-B 28718), cl 13.0 mm, cw 12.5 mm (MNHN-B 28724).

DESCRIPTION

Carapace ( Fig. 27 ) slightly longer than broad in males, most females; dorsal surface with conspicuous, short setae, small granules. Urogastric, cardiac regions elevated, urogastric region bordered by conspicuous lateral grooves; branchial grooves shallow. Branchial regions slightly inflated along sides.

Anterior border of carapace ( Fig. 27 ) with triangular, straight, acutely tipped outer orbital teeth, longer than but not reaching as high as frontal teeth. Frontal teeth longer and more conspicuous in males, acute to obtuse tips; lateral frontal teeth slender, nearly equal or slightly shorter than triangular median frontal teeth. Orbital sinuses broad, V-shaped, small, short vertical fissure at dorsal lower margin of each sinus; inner margins J-shaped, outer oblique except slightly rounded proximal portion anterior to orbital fissure; lateral frontal sinuses U-shaped, asymmetrical; medi- an frontal sinus V-shaped, wider than lateral frontal sinuses but as wide as orbital sinuses.

Eye peduncles ( Fig. 28A ) short, wide, slightly longer than or as long as cornea, immobile. Only tips of eyes barely visible dorsally.

Anterior border of endostome ( Fig. 28A ) lies well below posterior border of antennular fossae of basal antennular articles.

Male chelipeds (P1) smooth, equal or nearly equal, short setae on all articles, except fingers (scant on proximal portion of dorsal margin of dactyli); propodi slender, almost as long as fingers; fingers slender, with broad cutting edges. Female chelipeds similar to male chelipeds except few broad, round teeth on fingers.

P2, P3 ( Fig. 27 ) short, thick; scant, short setae on all articles (very scant, short on proximal portion of dactyli); length of P2 meri 0.8 times cl, P2 meri 5.2-5.7 times longer than broad. P4, P5 with short hairs; P5 dactyli relatively slender, curved.

Male abdomen ( Fig. 28B ) with four somites (3-5 fused, basal half swollen), triangular telson. Somite 1 length 2.2-2.8 times as broad, somite 6 rectangular. Female abdomen with six somites; broad, triangular telson; somite 3 broadest, somite 6 longest.

G1 ( Fig. 28C ) very slender; distal third narrow, straight, tips slightly rounded, short spines along tips, inner margins; G2 relatively short, each distal part broad; straight distal end, blunt tip.

REMARKS

Characteristic of Ethusina crenulata n. sp. is the presence of a small vertical fissure on the dorsal lower margin of each orbital sinus and the presence of short but conspicuous setae throughout the dorsal surface of the carapace and pereopods. One or both orbital fissures are sometimes absent or difficult to see, particularly in small females. Similar orbital fissures are present in Ethusa crassipodia n. sp. and in Ethusina isolata n. sp.

Similar to E. crenulata n. sp. are E. huilianae n. sp. and E. isolata n. sp. E. huilianae n. sp. is being described from the same deep-water stations in French Polynesia where E. crenulata n. sp. was collected (see below). Although only four large (cl 11.8 mm- 13.3 mm, MNHN-B 28727-28729, 28834) male specimens of E. huilianae n. sp. are known, there is ample morphological evidence to support the description of the two as separate species, even if both have similarly slender G1 ( Figs 27C ; 29C ). The main differences (see Table 1) are triangular, straight outer orbital teeth in E. crenulata n. sp. (slender, much longer, directed outwardly in E. huilianae n. sp.; Fig. 29 ), a fissure at the dorsal lower margin of each orbital sinus in E. crenulata n. sp. (absent in E. huilianae n. sp.), carapace with moderately inflated branchial regions in E. crenulata n. sp. (conspicuously inflated in E. huilianae n. sp.; Fig. 29 ), eye peduncles that are slightly shorter in E. crenulata n. sp. (slightly longer or as long as cornea, 2.1 times eye diameter in E. huilianae n. sp.), and shorter, thicker P2 and P 3 in E. crenulata n. sp. (P2 meri 0.8 times cl in contrast to 1.0-1.1 times cl in E. huilianae n. sp.). Similarities with E. isolata n. sp., being described from the Hawaiian Is, are more marked since both species share the presence of a fissure at each orbital sinus and females have relatively short and triangular outer orbital teeth ( Fig. 31A ). Differences between the three species are summarized in Table 1.

Figures

FIG. 27. — Ethusina crenulata n. sp., paratype cl 10.1 mm, cw 10.0 mm, French Polynesia, Marquesas Islands, Eiao, MUSORSTOM 9, stn CP 1276, 800-805 m (MNHN-B 28718).

FIG. 28. — Ethusina crenulata n. sp., holotype cl 9.8 mm, cw 9.6 mm, French Polynesia, Marquesas Islands, Eiao, MUSORSTOM 9, stn 1282, 416-460 m (MNHN-B 28717); A, ventral view of anterior portion of body; B, abdomen; C, left G1, ventral view (left), dorsal view (right). Scale bars: A, B, 2 mm; C, 1 mm.

FIG. 34. — Bathymetric distribution of Indo-West Pacific ethusine crabs.

FIG. 29. — Ethusina huilianae n. sp., holotype cl 12.7 mm, cw 13.0 mm, French Polynesia, Marquesas Islands, Eiao, MUSORSTOM 9, stn CP 1277, 1000-1100 m (MNHN-B 28727).

FIG. 31. — Ethusina isolata n. sp.; A, holotype cl 9.2 mm, cw 9.2 mm, Hawaiian Islands, Kauai, Albatross, stn 4028, 812-873 m (USNM 29933), dorsal surface of carapace and P2; B, paratype, 6.3 mm, cw 5.9 mm, Hawaiian Islands, Kauai, Albatross, stn 4132, 470-573 m (USNM 29934), left G1 ventral view with G2 in situ (left), dorsal view (right). Scale bars: A, 5 mm; B, 1 mm.