FAO Species Identification Guide for Fishery Purposes Western

1098 Crabs
Xanthidae XANTHIDAE
Xanthid stone and mud crabs
Diagnostic characters: Carapace hexagonal, transversely hexagonal to transversely ovate,sometimes
circular; dorsal surface usually ridged or granulose; frontal margin usually notched medially;
usually 2 to 6 spines, teeth and/or lobes on each anterolateral margin. Longitudinal ridges which define
the efferent respiratory current usually absent or strong only on posterior part of endostome; ridges not
visible on anterior part of endostome when mouthparts pushed aside. Fingers of chela may be spoontipped.
Legs varying in structure; propodus and dactylus with or without a special dactylo-propodal
articulation, which is formed by a rounded submedian extension of the lateral margin, shaped to slide
underneath a projecting button on the subproximal edge of the dactylus. Male abdominal segments 3 to
5 immovable, fused completely or incompletely. Male first gonopod slender, slightly sinuous; distal part
relatively simple, without complex folds, long setae usually present distally or subdistally; male second
gonopod very short, less than 1/4 the length of male first gonopod.
6
5
4
3
2
1
male abdomen
segments 3-5 fused
(completely or
incompletely)
Habitat, biology, and fisheries: Benthic crabs with diverse habits. Most species of minor or no commercial
importance. A single species of Atergatopsis (“egg crabs”) and 4 of the reef species of Etisus (“spooner
crabs”) are of interest to fisheries in the area.It is important to note here that several species of xanthids
are highly poisonous, particularly Zosimus aeneus, Lophozozymus pictor, andAtergatis floridus, and
their consumption has caused a number of human deaths (see General Remarks).
Similar families occurring in the area
The Xanthidae is a very diverse group and can easily be confused with a number of families. Particularly
difficult to distinguish are the Eriphiidae (likewise called “stone and mud crabs”) and Carpiliidae (reef crabs),
both of which were previously included in the Xanthidae.
Carpiliidae, Eriphiidae: adult males can be distinguished from xanthids by having the male first gonopods
stout and cylindrical (rather than slender and sinuous), and the male second gonopods very slender, longer
than the male first gonopod (rather than very short). Male eriphiids can also be distinguished from xanthids
by having all the male abdominal segments freely movable, with the sutures clearly visible (versus male
abdominal segments 3 to 5 completely fused, with sutures not dicernible).
all male
abdominal
segments freely
movable
Eriphiidae
Carpilidae
anterolateral
margin with
only 1 tooth