FAO Species Identification Guide for Fishery Purposes Western

1078 Crabs
3a. Uropods usually structurally
modified into a “rasp”
(Fig. 98a) and used for clinging
onto interior of gastropod
shells or hollow wood or underside
of bivalve shells, at
least in early crab stages . . . . . . → 4
3b. Uropods (may be absent)
not modified for clinging purposes,
no “rasp” present
(Fig. 98b); crabs not associated
with hollow or concave
objects even in early crab
stages . . . . . . . . . . . . . . . . → 9
4a. Abdomen bilaterally symmetrical, clearly divided
into segments, usually well calcified even at early
crab stages, pleurites (side plates) distinct;
shrimp- to lobster-like appearance, abdomen not
tucked under carapace (Fig. 99) . . . . . . . . Pylochelidae
4b. Abdomen usually bilaterally asymmetrical, not
clearly divided into segments, usually weakly
calcified or membranous, at least in early crab
stages, pleurites (side plates) absent; typical
hermit crabs or distinctly crab-like with abdomen
tucked under the carapace . . . . . . . . . . . . → 5
5a. Coxae of third maxillipeds close to each other, no
distinct gap between them (Fig. 100a); chelipeds
equal or unequal, when unequal, left chela larger ..... → 6
5b. Coxae of third maxillipeds distinctly separated
from each other, wide gap between them
(Fig. 100b); chelipeds unequal, with right chela
larger . . . . . . . . . . . . . . . . . . . . . . . . . . → 7
6a. Eyestalk laterally flattened (Fig. 101a); eyes usually
held subparallel to each other (Fig. 102a);
antennae laterally flattened, short; completely
terrestrial crabs (Fig. 103). . . . . . Coenobitidae (p. 1154)
6b. Eyestalk circular to subcircular in cross-section,
not laterally flattened (Fig. 101b); eyes
held obliquely to each other (Fig. 102b); antennae
long, subcylindrical in cross-section; completely
aquatic crabs (Fig. 104) . . . . . . . . . Diogenidae
eyes
laterally
flattened
eyes
cylindrical
a) Coenobitidae b) Diogenidae
Fig. 101 eye in dorsal view
rasp-like
structures
of uropod
uropod without
a) rasp-like structures b)
Fig. 98 posterior portion of body (dorsal view)
eyes held
subparallel
narrow gap
a) Coenobitidae
and Diogenidae
Fig. 99 Pylochelidae
coxa
wide gap
b) Lithodidae, Paguridae,
and Parapaguridae
Fig. 100 third maxillipeds
eyes held
obliquely
a) Coenobitidae b) Diogenidae
Fig. 102 relative position of eyes (dorsal view)