Description:-
Dorsal surface of carapace purplish anteriorly, covered with numerous large smooth isolated mammillary tubercles, which by their coloration (red base and shining yellow apex) exactly resemble ripe small-pox pustules. In the posterior half of the carapace the place of these well-defined "pustules" is taken by equally well-defined round or oval slightly-raised red patches. The upper external surface of the palm similarly displays “pustules” and “papules”. Preserved specimens in formalin appeared light yellowish white. Large round tubercles present on the hepatic and gastric regions of the carapace. The clypeiform expansion of the carapace not well developed. Carapace sub-circular; breadth exceeds length. The antero-lateral borders of carapace smooth in the anterior half whereas crenulated in the posterior half compared to the posterior borders. The posterior border granulated and bounded on either side by a faint prominence. The anterior part of the antero-lateral borders are somewhat smooth whereas the posterior half having 5/6 coarse serrations. The posterior margin of the carapace beaded, bearing a tooth on either side. The clypeiform expansions little developed bearing seven serrated teeth. The pterygostomian portion bears scanty marginal hairs. The antennae about twice the breadth of the orbit. The front sharply bilobed. The upper surface of wrist and outer surface of palm bears numerous bullous tubercles resembling those on the carapace. The crest of palm serrate. The abdomen resembles to that of Calappa lophos. The sternum corresponding to the walking legs inflated. The palm on the upper margin dentate (about seven in numbers) whereas the lower surface uniformly covered with bead like granules. The exopods and endopods of the third maxillipeds densely hairy on their inner margins; inner margin of ischium with minute rounded teeth. Only the propodi and dactyli hairy marginally in second maxillipeds. Smaller lobe of first maxilliped bears marginal hairs. Scaphognathite of second maxillae longitudinally hexagonal with minute marginal hairs on the lower inner boarder. First maxillae hairy on the upper margin. Dentate margin not present on ventral view of mandible; posterior region dorsally carinated. Antennae longer than antennule.
Synonyms:-
Cancer gallus Herbst, 1803; Cancer (Calappa) gallus Latreille, 1816a; Gallus gallus de Haan, 1833-1849 (1837); Calappa gallus Milne Edwards H., 1837;Calappa gallus capellonis Laurie 1906; Jayabaskaran et al. 2000;Calappa gallus, Tirmizi & Kazmi 1988; Kumar et al. 2007.
References:-
Alcock,A. (1895-1900). Materials for the Carcinological Fauna of India (Nos. 1-6. The Brachyura, Oxyrhyncha, Oxystoma, Cyclometopa, Primigenia or Dromiacea and Catometopa or Grapsoidea). J. Asiat. Soc. Beng., 64: 157-291, 65: 134-296, 67:67-233, 68: 1-104 and 123-169, 69: 279-456 (Reprinted in 1984, International Books and Periodical Supply Service, New Delhi).
Biju Kumar, A., Sushil Kumar, M, and Galil, B.S. (2013). Calappid and leucosiid crabs (Crustacea: Decapoda: Brachyura) from Kerala, India, with the description of a new species of Mursia Desmarest, 1823, from the Arabian Sea and redescription of M. bicristimana Alcock & Anderson, 1894. Zootaxa, 3746 (4): 529-551.
Sushilkumar, M. (2013). Diversity and proximate composition of brachyuran crabs in the trawl by-catch of Kerala coast. PhD Thesis submitted to University of Kerala, India.