Common name: Viola
Latin Origins: becoming violet
Distribution: Nicobar Islands; Phuket, Thailand; Cebu Island, Philippines; several Japanese Islands; Tanzania and Zanzibar.
Ecology: Supralittoral; juveniles frequent mangrove forests; adults frequently found on beaches.1
Characteristics:Entire body violet purple, but varying from light lavender to dark violet; dark patch of brown on outer lower surface of palm of left cheliped.2 Juveniles are pale to orange or red with colors darkening as the crab ages. Eyes are elongated with the stalks being almost entirely black.
Dorsal surface of shield with scattered granules and punctations, lateral projections produced and each with terminal spinule; rostrum broadly triangular, not produced beyond level of lateral projections. Ocular peduncles compressed, reaching almost to mid-length of ultimate antennal peduncular segment; dorsal surfaces with numerous short setae; ocular acicles narrowly triangular, approximate. Antennular peduncles extremely long; basal peduncular segment (Fig. 1) with broad, roundly subrectangular dorsal lobe; lower ramus of flagellum (Fig. 2) approximately half length of upper. Antennal acicle (Fig. 3) fused with second peduncular segment. Each chela with tuft of dense setae on upper inner margin. Left cheliped without stridulating ridge on upper outer surface of palm (Fig. 4), but with numerous scattered granules on upper half of outer face, fewer on lower half and lower central region nearly smooth; lower margin of palm straight or slightly concave, lower proximal angle produced into lobe-like projection. Left third pereopod with lateral surface of propodus (Fig. 5) nearly smooth, separated from dorsal surface by well-marked longitudinal crest in anterior half, dorsomesial margin (Fig. 6) prominently projecting inward, upper half of mesial surface concave, median portion convex and with low ridge delineating concave ventromesial surface; dactyl broad, short, with dorsolateral margin (Fig. 5) distinctly angular, lateral face weakly convex, mesial surface (Fig. 6) with concave lower portion marked by distinct longitudinal ridge. Coxae of males (Fig. 7) subequal, approximate, both thick and short, each with dense tuft of setae; no sexual tubes developed; sternal protuberance relatively small. Telson (Fig. 8) with distinct incision separating anterior and posterior portions; terminal margins unarmed but with long dense setae over entire length.3
References: 1. MCLAUGHLIN 1997, 2. NAKASONE 1988, 3. Heller 1862,