FAO Species Identification Guide for Fishery Purposes Western

Raninidae 1089
Raninidae RANINIDAE
Spanner crabs
Diagnostic characters: Carapace longitudinally
ovate; dorsal surface strongly granulose
or squamose to smooth; front triangular, narrow.
Third maxillipeds very narrow, merus
distinctly triangular. Eyestalks long, longer than
front. At least one pair of legs with last 2 or 3
segments paddle-like. Thoracic sternum very
narrow, especially sternites 5 to 7. Allmale
abdominal segments distinct, movable.
Habitat, biology, and fisheries:
Spanner crabs burrow in soft
substrates and tend to occur in
moderately shallower waters.
They are absent or rare in continental
shelf waters and prefer
more saline waters. They feed on
a variety of worms and softshelled
molluscs. Most species
are moderately small and are not
often encountered. A single species,
Ranina ranina, is large and
triangular
merus
abundant enough to be fished
commercially.
right 3
carapace
longitudinally
ovate
rd
maxilliped
Similar families occurring in the area
The combination of a longitudinally ovate, elongate carapace
with its very narrow thoracic sternum, and the narrow
third maxillipeds with a triangular merus easily distinguish
raninids from other crab families. The following 2 families
look superficially similar to the Raninidae:
Homolidae: carapace similarly longitudinally elongate, but
subcylindrical in shape; last pair of legs reduced, subchelate,
turned upwards and adapted for carrying objects.
Corystidae (non-commercial): many species similar in
body shape, but have broader and more rectangular
mouthparts, a broader thoracic sternum, and never have
any of their legs paddle-like and possess a pair of very
long and highly setose antennae.
fingers
strongly bent
at least 1
pair of legs
paddle-like
Homolidae
last leg reduced,
subchelate
References
Brown, I. W. 1986. South Queensland’s spanner crabs - a growing fishery. Australian Fisheries, 45(10):3-7.
Ihle, J.E.W. 1918. Die Decapoda Brachyura der Siboga-Expedition. III. Oxystomata: Calappidae, Leucosiidae, Raninidae.
Siboga Exped. Monogr., 39b(2):159-322.