Acanthodromia margarita (Alcock, 1899)

Ng, Peter K. L. & Jeng, M. - S., 2017, Notes on two crabs (Crustacea, Brachyura, Dynomenidae and Iphiculidae) collected from red coral beds in northern Taiwan, including a new species of Pariphiculus Alcock, 1896, ZooKeys 694, pp. 135-156 : 135-137

Acanthodromia margarita (Alcock, 1899) Figs 1 A–C, 2, 3

Dynomene margarita Alcock, 1899: 19, pl. 2: fig. 3.

Acanthodromia margarita - Alcock 1900: 134; Sakai 1965: 43; Sakai 1976: 31, pl. 7: fig. 2; Nagai 1989: 43; McLay 1999: 539, fig. 31; Marumura and Kosaka 2003: 20; McLay and Ng 2005: 18, fig. 5; Ng et al. 2008: 37.

Material examined.

Taiwan: 1 female (17.8 × 18.3 mm) (ASIZ 75484), waters of Zone A (precious coral fishing ground), Peng-Chia-Yu Island, 60 km northeast of Keelung, 25°37.901'N, 122°28.577'E, 175 m, Taiwan, coll. Fishing Vessel "De-Cheng 136", M.-L. Chang, 14 May 2017. Philippines: 1 male (14.7 × 17.7 mm) (ZRC 2001.358), Balicasag Island, 200-300 m, coll. December 2000; 1 male (10.5 × 11.5 mm), 2 females (7.8 × 8.3 mm, 11.2 × 12.2 mm), 2 ovigerous females (14.7 × 16.7 mm, 17.0 × 18.5 mm) (ZRC 2003.668), 1 male (9.9 × 10.6 mm), 1 female (12.3 × 13.4 mm) (MNHN); Balicasag Island, 200 -300 m, 25 -30 Jul 2003; 1 male (14.7 × 15.8 mm) (ZRC 2008.1425), station PN1, Balicasag Island, 200 -300 m, coll. November 2003; 1 female (no pereopods left, 11.2 × 12.0 mm) (ZRC 2008.1426), Balicasag Island, 200-300m, coll. November 2003-April 2004; 1 male (15.3 × 16.7 mm) (ZRC 2008.1419), station PN1, Balicasag Island, coll. 29 May 2004; 1 female (17.7 × 19.2 mm) (ZRC 2008.1420), Balicasag Island, coll. 29 March 2004; 5 males (8.8 × 10.6 mm, 11.2 × 12.5 mm, 11.3 × 13.0 mm, 13.5 × 14.2 mm, 14.1 × 16.2 mm), 2 females (15.4 × 17.2 mm, 15.8 × 17.0 mm), 1 female (carapace cracked) (ZRC 2004.596), Balicasag Island, coll. 2 March 2004; 1 male (11.3 × 12.7 mm) (ZRC 2008.1043), Balicasag Island, coll. May 2004 [all above locations at 9.518891°N, 123.680511°E, Panglao, Bohol, Visayas, Philippines; purchased from local shell fishermen, obtained by tangle nets]; 1 male (13.9 × 15.3 mm), 2 females (14.2 × 15.0 mm, 15.7 × 16.1 mm) (ZRC 2013.372), Maribojoc Bay, Panglao, Bohol, Philippines, coll. J. Arbasto, 30 May 2004; 1 female (14.2 × 15.0 mm) (ZRC 2007.207), Maribojoc Bay, Panglao, Bohol, Philippines, coll. J. Arbasto, July-May 2005.

Description.

Colour. McLay and Ng (2005: 18) described the fresh colour of Philippine specimens as "light pink spines on carapace and the pereopods with golden yellow dactyli". The present Taiwan specimen is orange-yellow on all its dorsal surfaces, with the spines orange-pink with white tips (Fig. 1A, B). In some Philippine specimens, the carapace can be a more striking pink and the pereopods orange-yellow with the spines pink (Fig. 1C).

Remarks.

The present female specimen from Taiwan is one of the largest on record and agrees well with published descriptions and figures of the species. The frontal margin appears to vary in form due to the relative strength of the frontal spines, particularly the median pseudorostral one. The two large rounded, basally fused tubercles on pleonal somite 4 is distinct in both sexes; with those in some of the smaller specimens appearing almost completely fused, forming one structure (Fig. 3B). The posterior margin of the epistome always has four spines, but the structure of the two median ones varies slightly, from directly pointing downwards (e.g., McLay and Ng 2005: fig. 5B) to curving medially (Fig. 2C).

Distribution and depth.

Acanthodromia margarita was described from the Andaman Sea in the eastern Indian Ocean, and has been also reported from Japan, Philippines, and now Taiwan. The Indian Ocean specimen was from relatively shallow water (135 m), but the series from the Philippines was from 120-300 m depth. The present Taiwan specimen was collected from a depth of 175 m.