FAO Species Identification Guide for Fishery Purposes Western

1112 Crabs
Pilumnidae PILUMNIDAE
Diagnostic characters: Carapace hexagonal,
transversely rectangular or
transversely ovate; dorsal surface convex,
smooth to granulated; frontal margin entire to
multilobate; usually 1 to 4 teeth or lobes on
each anterolateral margin. Longitudinal
ridges defining efferent respiratory current
usually well developed along entire
endostome, ridges visible on anterior part of
endostome when mouthparts pushed aside.
Legs normal. Male abdominal segments 3 to
5 freely movable. Male first gonopod slender,
usually S-shaped, distal part simple;
male second gonopod very short, sigmoid.
Habitat, biology, and fisheries: Benthic
crabs with diverse habits. Most species in this
family are of no commercial value. The moderately
large-sized Galene bispinosa has minor
economic importance.
Hairy crabs
Remarks: Despite their common name, “hairy crabs”, many pilumnids (including Galene bispinosa) are
actually not very setose (or “hairy”).
Similar families occurring in the area
The Pilumnidae is a very diverse group and its taxonomy
remains unsettled. As their general (usually hexagonal)
carapace shape is similar to those of xanthids, eriphiids,
and goneplacids, the safest way to identify a pilumnid
species is to examine the male abdomen and gonopods.
All pilumnids share very similar male abdominal, male
pleopodal, and larval characters.
Xanthidae: male abdominal segments 3 to 5 fused (instead
of freely movable).
Eriphiidae: male first gonopods stout (rather than slender
and sinuous); male second gonopods long (rather than
very short).
all male abdominal
segments freely movable
Xanthidae
male abdominal
segments fused,
immovable
Goneplacidae: generally have stouter male first gonopods and/or proportionately longer male second
gonopods; some species with male abdominal segments 3 to 5 fused.
Eriphiidae Goneplacidae
References
Balss, H. 1933. Beitrage zur Kenntnis der Gattungen Pilumnus (Crustacea Dekapoda) und verwandter Gattungen.
Capita Zoologica, 4(3):1-47.
Ng, P.K.L. 1987. The Indo-Pacific Pilumnidae II. A revision of the genus Rhizopa Stimpson, 1858 and the status of the
Rhizopinae Stimpson, 1858 (Crustacea: Decapoda: Brachyura). Indo-Malayan Zoology, 4(1):69-111.