FAO Species Identification Guide for Fishery Purposes Western

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Gecarcinidae 1147
Gecarcinidae GECARCINIDAE
Land crabs
Diagnostic characters: Carapace circular to
transversely ovate; dorsal surface
smooth, strongly convex longitudinally and
transversely; frontal margin entire; anterolateral
margins unarmed or each with a single tooth.
Rhomboidal gap present between third maxillipeds.
Legs stout, dactylus longitudinally ridged,
often with dense, stiff setae, margins with spines.
All male abdominal segments distinct, movable.
Habitat, biology, and fisheries: Terrestrial crabs.
Although gercarcinids can be found many kilometres
inland, they must return to the sea to spawn
and release their planktonic larvae. The most frequently
collected food species in the area is Cardisoma
carnifex.
Similar families occurring in the area
The swollen carapace and terrestrial habitats of the gecarcinids make them a very distinctive group. In this
respect they may be confused with several fresh-water and terrestrial genera of Gecarcinucidae, Potamidae,
and Parathelphusidae (species of the latter 2 are collected for food in many parts of Southeast Asia
and Indo-China).
Potamidae, Gecarcinucidae, Parathelphusidae (= Sundathelphusidae): several genera of these exclusive
fresh-water families may resemble gecarcinids, but are readily distinguished by the lack of a rhomboidal
gap between the third maxillipeds.
Grapsidae: also have a rhomboidal gap between the third maxillipeds, but most species possess a much
flatter dorsal carapace surface compared to gecarcinids.
Ocypodidae: also have many terrestrial members, but lack a rhomboidal gap between the third maxillipeds
and generally do not have as thick a shell as seen in gecarcinids.
very narrow front
long orbits
Grapsidae carapace generally
flatter
Ocypodidae
Key to species of interest to fisheries occurring in the area
1a. Exopod of third maxilliped without flagellum (Fig. 1a); orbits oblique, eyes small, never
reaching first anterolateral tooth (Fig. 2) . . . . . . . . . . . . . . . . . . . . . Gecarcoidea lalandii
1b. Exopod of third maxilliped with long flagellum (Fig. 1b); orbits horizontal, eyes well
developed, reaching to just before first anterolateral tooth . . . . . . . . . . . . . . . . . . . . .→ 2
exopod
short, no
flagellum
a) Gecarcoidea lalandii
b) Cardisoma spp.
Fig. 1 third maxilliped
exopod
with long
flagellum
eyes
small
Fig. 2 Gecarcoidea lalandii