Trapezia digitalis   Latreille,  1828 (Crab)
Organism information awaits expert curation
Class: Malacostraca

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Color: Adults dark brown in color; Carapace, upper surface of chelipeds and eyes dark brown. Thin, light brown band oftern along anterior border of carapace and anterior and distal borders of merus of chelipeds.

Adults with indistinct notch at junction of anterolateral and posterolateral borders. Frontal margin sinuous, barely divided from supraorbital angle.

Materials: 6 males (cw. 5.5 - 13.4 mm), Semales (cw. 12.0 - 12.3 mm) Anterolateral borders of carapace always parallel in fully grown individuals and juveniles. Epibranchial tooth as acute tooth in juveniles but even reduced to notch until disappearance in most adults. Posterolateral borders converging posteriorly. Postorbital angles and inner suborbital teeth acute in juveniles but growing progressively less pronounced with age. Frontal border consisting of supraorbital angles and four lobes, all cut from each other by slight emarginations. In many fully grown individuals separation between numerous minute teeth. Third maxillipes subrectangular. Ischium of endognath. With scattered punctae but no granulations. Suture (sternal suture 2/3) between second and third thoracic sternites only in juveniles and smallest adults. Suture always absent in fully grown individuals although junction of sternites may be marked by light-color scar in some. Chelipeds slender and relatively short and slightly unequal. Meri fringed with teeth that vary in size and number. Teeth more acute in juveniles while tooth on anterior proximal margin always obtuse, short setae. Sometimes as short and sparse tomentum, along outer margins of carpus and propodus. Upper margin of propodus rounded; lower margin cristate with few microscopic and flattened teeth. Light-colored, node-like tubercle at distal end of inner surface of propodus at base of dactyli. Fingers short and curved. Dactylus and immovable finger of largest cheliped typically armed with sharp teeth that decrease in size distally; fingers of smallest cheliped armed with cutting edges. Walking legs thick and stocky. Few slender, short setae on upper margins of carpus (distal portion only) and propodus. Setae more numerous along upper margin of dactyli. Inner (posterior) margins of dactyli with three pairs of horny setae and three transversal rows of shorter setae proximally. First pleopod of male relatively short, with stout, symmetrical apex. Short distal spines along both surfaces and simple setae near base.

Obligate symbionts of the corals Pocillopora species.

Synonym (s)
Trapezia digitalis var. typica Borradaile, 1902
Trapezia fusca Hombron & Jacquinot, 1846
Trapezia leucodactyla Ruppell, 1830
Trapezia nigrofusca Stimpson, 1860

Common Name (s)
Economic Importance and Threats

Habitat:  Reef Associated


• Lakshadweep INDIA
• Andaman and Nicobar Islands INDIA
• Tamil Nadu INDIA

Literature Source(s)
  • Jeyabaskaran, R; Wafar, S and Wafar, M (2002) CD on Brachyuran Crabs of West Coast, India Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Available at -
  • Deb, M and Rao, GC (1993) A check-list of the brachyuran crabs (Crustacea: Decapoda)of Bay islands Journal Of The Andaman Science Association Andaman Science association, Port Blair 8(1-2) 25-34 Available at - NIO, Goa
  • Roy, MKD and Nandi NC (2007) Brachyuran diversity in coastal ecosystems of Tamil Nadu Journal of Environment and Sociobiology Social Environmental and Biological Association, Kolkata, India 4(2) 169-192 Available at - NIO,Goa

Page last updated on:2011-10-11

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