Gelasimus jocelynae (H. -T. Shih, Naruse & P. K. L. Ng, 2010)

Michie, Laura A., Barnes, R. S. K., Clark, Paul F., Bennett, Wayne A. & Cragg, Simon M., 2021, Distinguishing ten sympatric species of fiddler crab (Decapoda: Ocypodidae) using a suite of phenotypic characteristics, Zootaxa 5026 (4), pp. 480-506 : 491-493

Gelasimus jocelynae (H.-T. Shih, Naruse and P.K.L. Ng, 2010)

( Figure 7a–j )

Material examined. 10 ♀, 10 ♂, Kaledupa , Indonesia, 5º 29’ 49’’S, 123º 45’ 21’’E, mud flat southwest of boat jetty, coll. L. Michie, 27.08.2014 . 10 ♀, 10 ♂, Kaledupa , Indonesia, 5º 29’ 51’’S, 123º 45’ 20’’E, mud flat in front of mangroves, coll. L. Michie, 27.08.2014 .

Diagnosis. Carapace: slightly broader than long; smooth; front narrow, practically straight; anterolateral angles acute, slightly produced; anterolateral margins short; dorsolateral margins short or nearly absent. Major cheliped: elongated dactyl and pollex; pollex with distinct wave pattern occurring near middle of the gape, hook like tooth distally.

Colouration ( Figure 7a–d ).Adult male. Carapace: variable, nearly always light/dark brown or grey with varying degrees of markings in colours including blue, aqua, orange and white, anterior ventral surface and third maxillipeds normally light brown or grey. Major cheliped: dactyl generally white extending dorsally to manus, pollex often with white tip, remainder of pollex orange extending to manus, carpus is grey or white dorsally and orange ventrally, remainder of cheliped either white or orange, in young adult males manus or pollex has a small brown mark. Minor cheliped & ambulatory legs: generally brown or grey.

Adult female. Similar to males. Chelipeds: often orange.

Juvenile male. Carapace: most often light brown. Major cheliped normally white at juvenile stage, often with brown mark, similar to adults.

Juvenile female. Normally like juvenile male.

Gonopod morphology ( Figure 7e–h ). G1 curved in dorso-lateral direction; simple flanges; pore of sperm channel small; distal protuberance relatively short, wide, can vary, often reaching beyond base of flange.

Gastric mill ( Figure 7i, j ). Urocardiac ossicles moderately complex, with 4 pairs of ridges on median tooth plate, 1–3 decreasing in size distally, larger gap between third and fourth, fourth large and attached to plate dorsally; stem with setae present on lateral margins of posterior stem region. Lateral tooth plate with 18 comb-shaped.

Biology. Gelasimus jocelynae is a relatively small-size species (largest male CL = 10.6 mm, CB = 16.4 mm, largest female CL = 9.4 mm, CB = 14.3 mm); one of most abundant species on shore, present in mid and low intertidal zones.

Distribution. Pacific islands west of Fiji, including Japan, Taiwan, the Philippines, Indonesia, Papua New Guinea, and Vanuatu.

Remarks. Gelasimus jocelynae is distinguished by the distinct wave pattern occurring near the middle of the pollex, the hook like distal tooth and the colouration, specifically the white dactyl and orange pollex. The specimens examined fit the original description, but this is the first description of the gastric mill for G. jocelynae which is similar to that of G. tetragonon described here and Gelasimus vocans described by Shih (2015).

Figures

FIGURE 7. Gelasimus jocelynae H.-T. Shih, Naruse and P.K.L. Ng, 2010: a–d Sulawesi Tenggara, Indonesia. Adult male colouration; a, large chela; b, carapace dorsal view. Adult female colouration; c, frontal view; d, carapace dorsal view. Photos credit L. Michie. Line drawing of right G1; e, mesial view; f, lateral view; CLSM images of apical part of G1; g, mesial view; h, lateral view; SEM photos of male gastric mill; i, median tooth plate, ventral view; j, left lateral tooth plate, mesial view.