Xanthid crabs, decapod crustacean, with the black coloured fingers, are easily found under rocks or stones in the intertidal or subtidal zones. Two xanthids,
Many members of the family Xanthidae MacLeay, 1838, with the black coloured fingers, occur in the Indo-West Pacific. They are easily found around the intertidal or subtidal zones, and hide under the rocks or in the sponges and other sessile invertebrates, and graze on alge or on detritus.
Until now, 28 species of 24 genera belonging to the family Xanthidae have been recorded among Korean fauna (Lee et al., 2012). As a result of continuous taxonomic studies on Korean crabs, two xanthid crabs,
Materials examined in this study were preserved in 95% ethyl alcohol, and deposited in the Marine Arthropod Depository Bank of Korea (MADBK), Seoul National University. The specimens were observed under a microscope (Model M165C; Leica, Wetzlar, Germany). Drawings were made with the aid of camera lucida. Images were recorded using Digtal camera (Model Nikon D800; Nikon Imaging Korea Co., Ltd., Korea), and developed with the software (Model Helicon Focus; Helicon Soft Ltd., Kharkov, Ukraine).
The abbreviation “cl” and “cw” referred to the carapace length from the front to the posterior dorsal margin of the carapace and to the width of the carapace measured at the wides part, respectively. The zones of the carapace (1-3M, 1F, 2F, 1-4L, and 2P) were divided according to Dana (1853) and Serène (1984). The classification followed that of Ng et al. (2008).
Order Decapoda Latreille, 1802Family Xanthidae MacLeay, 1838Genus Etisus H. Milne Edwards, 1834
Etisus laevimanus Randall, 1840: 115; Forest and Guinot, 1961: 88; Sakai, 1976: 455, fig. 245, Pl. 161, fig. 1; Dai and Yang, 1991: 324, fig. 164B(5), Pl. 42(2).Etisus convexus Stimpson, 1858: 31; 1907: 36, Pl. 5, fig. 2.Etisus (Etisus) laevimanus: Holthuis, 1953: 21.
[Fig. 1.] Etisus laevimanus Randall, 1840, male (cl 28.3 mm, cw 44.8 mm). A, Whole animal, dorsal view; B, Anterior view; C, Ventral view. cl, carapace length from the front to the posterior dorsal margin of the carapace; cw, with of the carapace measured at the widest part.
[Fig. 2.] Etisus laevimanus, male (cl 28.3 mm, cw 44.8 mm). A, Left cheliped, dorsal view; B, Anterolateral border, dorsal view; C, Right cheliped, outer view; D, Left cheliped, outer view. cl, carapace length from the front to the posterior dorsal margin of the carapace; cw, with of the carapace measured at the widest part.
[Fig. 3.] Etisus laevimanus. A, Left third maxilliped; B, Male abdomen; C, Female abdomen; D, Left male first gonopod, ventral view; E, Tip of left male first gonopod, ventral view. Scale bars: A-D=5 mm, E=0.5 mm.
Chelipeds (Figs. 1A, 2A, C, D) massive, robust, unequal. Chelipeds about 2.5 times as long as carapace length. Carpus with an obtuse tooth at the inner angle. Propodus depressed, subequal to finger in length; immovable finger with 1 obtuse tooth at sub tip. Dactylus of major chela depressed, with 2 obtuse teeth on inner margin. Fingers dark brown and pigment extended into proposes.
Ambulatory legs (Fig. 1A) short, heavy, moderately setose, shorter than carapace length; upper and lower border with hairs; anterior and posterior surfaces naked. Dactylus proximally bearing small, slightly elevated condyle abutting locking arch on distal margin of propodus, distally terminating in elongated corneous tip.
Male abdomen (Fig. 3B) narrow, elongated; third to fifth somites fused, lateral lobes of fused third somite weakly sculptured, granular, somite suture limited to slight indentations in lateral margin; sixth segment subrectangular; telson triangular and shorter than the sixth segment. Female abdomen (Fig. 3C) naked, covered sternum; all segment separated.
First pleopod of the male (Fig. 3D, E) curved ventrally and serrated along the margins. Second gonopod small, short, extending about 1/4 length of first gonopod, slightly swollen terminal bulb narrowing to sharp spine.
Xanthodes elegans Stimpson, 1858: 33; 1907: 47, Pl. 5, fig. 3.Xanthias atromanus Haswell, 1882: 49.Paraxanthias elegans: Sakai, 1976: 430, fig. 226, Pl. 155, fig. 2; Dai and Yang, 1991: 300, fig. 156B(3), Pl. 38(5).Xanthias elegans: Serène, 1984: 191 (key), 194 (key).
[Fig. 4.] Paraxanthias elegans Stimpson, 1858, male (cl 8.8 mm, cw 13 mm). A, Whole animal, dorsal view; B, Anterior view; C, Ventral view; D, Chelipeds, outer view. cl, carapace length from the front to the posterior dorsal margin of the carapace; cw, with of the carapace measured at the widest part.
[Fig. 5.] Paraxanthias elegans. A, Left third maxilliped; B, Male abdomen; C, Left male first gonopod, ventral view; D, Tip of left male first gonopod, ventral view; E, Tip of left male first gonopod, dorsal view. Scale bars: A-C=1 mm, D, E=0.3 mm.
Chelipeds (Fig. 4A, D) stout, asymmetrical. Merus smooth with its outer surface; inner surface concave; anterior margin granulate. Carpus sculpturesque with outer surface; upper surface dentiform, and with 2 teeth at inner-distal angle. Propodus smooth on surface except for dorsal surface; dorsal surface situated longitudinal groove along outer border; upper- outer surface furnished with large tubercles arranged in rows, forming irregular crests; dactylus stout, with teeth on cutting edges; immovable finger of minor chelipeds with distinct longitudinal groove along the middle of the outer surface.
Ambulatory legs (Fig. 4A) comparatively stout. Merus naked on both surface, with hairs and row of conical granules on upper border. Carpus, propodus and dactylus are densely covered with several long hairs. Upper borders and surfaces carpus and propodus armed with rather sparse conical granules. Upper surface of the carpus with longitudinal row. Dactylus much narrower than propodus, armed also with several sharp, more or less elongate granules on upper surface and with thick yellow, semitransparent spinules on upper border near terminal claw.
First gonopod (Fig. 5C−E) with distal portion curved laterally, finger-shaped at tip and armed with long feathery hairs on inner side.