Metacarcinus gracilis

Morphology

Like the other members of the family Cancridae, the slender crab has a very broad and oval carapace with dull, tooth-like protrusions toward the front of the carapace. Female crabs can be distinguished from males by a broad tail flap on their undersides, which are used for protecting their eggs when they are gravid. The slender crab carapace is usually olive brown, and its legs vary from yellowish brown to purple. M. gracilis only grows to a width of about 3.5 in and resembles a juvenile M. magister (Dungeness Crab). Often the two species can be confused, as M. gracilis looks very similar to a juvenile Dungeness crab. They can readily be distinguished from each other, though M. gracilis has a notch behind the widest point of its carapace that M. magister lacks, and the top joint of its pincers are not serrated like those of M. magister. More obscure ways to tell are by the appearance of hair on the posterior three legs of M. magister where M. gracilis is almost always hairless. Another telling characteristic of the slender crab is that the last segment of its tail flap is pointed, where M. magister is curved.

References

References

1. (2008). "Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world". [[Raffles Bulletin of Zoology]].
2. Eugene N. Kozloff. (1983). "Seashore Life of the Northern Pacific Coast". [[University of Washington Press]].
3. J. Dale Nations. (1975). "The genus ''Cancer'' (Crustacea: Bachyura): systematics, biogeography, and fossil record". Natural History Museum of Los Angeles County Science Bulletin.
4. (1999). "Phylogenetics of ''Cancer'' crabs (Crustacea: Decapoda: Brachyura)". [[Molecular Phylogenetics and Evolution]].
5. (2006). "Ectosymbiotic behavior of ''Cancer gracilis'' and its trophic relationships with its host ''Phacellophora camtschatica'' and the parasitoid ''Hyperia medusarum''". [[Marine Ecology Progress Series]].