Indo-Pacific Swimming Crab

Charybdis hellerii has a hexagonal carapace which is convex and covered in long, soft hairs. There are grainy transverse ridges present on frontal, protogastric, mesogastric and branchial regions. There are six prominent frontal teeth: two sharp inner orbitals plus four blunt submedian teeth, the median teeth have an elliptical lower plane which projects beyond the submedian teeth, the lateral teeth are acutely triangular, separated from the submedian teeth by a deep V-shaped cleft. The inner supraorbital lobe is roughly triangular and the outer infraorbital lobe has a convex margin; there are six sharp teeth on the anterolateral margin which have black, brown or red tips and are separated by deep notches and of which the most anterior tooth is the smallest. The basal antennal article is swollen and excludes the antennal flagellum from the orbit. The claws are large, unequal and are covered in short, fine hairs with three spines on the anterior margin of the merus and a small spine at towards the tip. The carpus has a strong spine on the interior margin and three ridges on the external surface; chela has four spines on upper surface and a single spine close to the carpal joint, lower surface smooth. The merus and carpus of the fifth leg has a spine on posterior margin, the posterior margin of the propodus is toothed, the dactyl is oval in shape. …

Charybdis hellerii occurs in a number of different habitats from the intertidal zone down to around 50 m in depth. It lives in areas with softer substrates like sand or mud flats so long as there are some stones. It also occurs in habitats with hard substrates where it can hide under rocks and among live corals, in tidal rock pools, among meadows of Thalassia and on mangrove roots (Rhizophora mangle). The juveniles have been observed co-existing in association with the bryozoan Schizoporella unicornis.