Trapezia formosa   Stimpson,  1869 (Crab)
Organism information awaits expert curation
Class: Malacostraca

Image copyrights: NIO, Goa

Color: Live specimens were described as very light brown in color but those preserved in alcohol are very light orange; Carapace and walking legs reddish orange. Eyes greenish grey. Dorsal portion of chelipeds dark reddish orange in sharp contrast with ventral portion of inner surface, which is orange-yellow to deep orange.

The frontal border is nearly straight and finely denticulate and the lateral borders of the carapace are never provided with a tooth or notch,not even in juveniles.

36 Females (cw. 5.0 - 10.0 mm), 35 males (cw. 3.8 - 9.3 mm). Anterolateral borders of carapace markedly curved in all individuals except juveniles and small adults, where they are less curved. Anterior branchial region slightly inflated so carapace has conspicuous globular appearance. Epibranchial tooth as small obtuse tooth in juveniles and slight notch in small adults; absent or barely noticeable in most fully grown individuals. Postorbital angles acute in juveniles and obtuse in adults. Frontal border wide, arched and cut by shallow emarginations into two rounded supraorbital angles and four lobes. Medium lobes typically rounded. The four lobes and supraorbital angles of juveniles and adults armed with numerous irregular, minute teeth, more noticeable on submedian lobes, barely noticeable on supraorbital angels. Third maxillipeds subrectangular. Ischium of endognath smooth, with scattered punctate but no granulation. Suture between second and third thoracic sternites (sternal suture 2/3) of juveniles and smallest adults, but absent in adults. Chelipeds, especially larger one, distinctively thick and bulky, with short and stubby fingers. Merus of chelipeds with teeth varying in size and number, even between right and left meri of same individual.

Teeth more acute in juveniles. Distal and proximal angles along anterior margin of carpus of juveniles and adults with two rounded, obtuse teeth. Few scattered and short setae may be present along outer margins of carpus and propodus. Upper margin of propodus rounded or with very slight crest; lower margin slight crest and slightly rounded. Dactylus and immovable finger of largest cheliped typically shorter and thicker, armed with large teeth. Smaller cheliped with more slender fingers armed with cutting edges. Walking legs thick and stocky. Upper margins of carpus and propodus with only few setae, except first pair, where few long setae may be found on distal portion of carpus. Setae more numerous along upper margin of dactyli. Few plumose setae. Inner (posterior) margin of dactyli with five or six horny setae and three to four transversal rows of shorter setae proximally. First pleopod of male relatively short and with stout, symmetrical apex similar to that of Trapezia digitalis. Short distal spines along both surfaces and proximal plumose setae.

Color variations throughout the geographic distribution obligate symbiont of Pocillopora corals.

Synonym (s)
Trapezia formosa Smith, 1869

Common Name (s)
Economic Importance and Threats

Habitat:  Reef Associated


• Lakshadweep INDIA
• Andaman and Nicobar Islands 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 -

Page last updated on:2010-11-23

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