How to Distinguish from Similar Species: This is the only decorator crab with the long hooked spine behind the eye. The carapace does not have a sharp anterolateral projection as seen in Pugettia producta. Geographical Range: Bering sea to Monterey, CA; Japan Depth Range: Intertidal to 436 m deep Habitat: Most abundant on mixed composition bottoms Biology/Natural History: This crab decorates more liberally than any of the other decorator crabs in this area. During decoration, pieces of material are attached to specialized hooked setae and also interact with pappose setae. The crab's chelae are small and delicate. In males the chelipeds are longer than the walking legs, but in females they are shorter. Will eat carrion. Predators include Pacific halibut (Hippoglossus stenolepis). In Puget Sound area, eggs may be carried during most seasons. Recently hatched eggs are orange-red; eggs nearly ready to hatch are reddish-brown. While the large majority and abundant species of true (Brachyuran) crabs walk sideways, members of genus Oregonia walk forward. In a 2025 preprint, Taniguchi et al. speculate that the sideways walking in so many true crab species is is because walking sideways allows for rapid escape locomotion options in two directions, providing a selective advantage.
References:Dichotomous Keys:Coffin, 1952 Flora and Fairbanks, 1966 Hart, 1982 Kozloff 1987, 1996 Smith and Carlton, 1975 Wicksten, 2009 General References:
Scientific Articles:
Taniguchi, Cunya, Tsubasa Inoue, Kano Kohara, Jung-Fu Huang, Atsushi Hirai, Nobuaki Mizumoto, Fumio Takeshita, and Yuuki Kawabata, 2025. Evolution of Sideways locomotion in crabs (Preprint). doi: General Notes and Observations: Locations, abundances, unusual behaviors: ![]() Note large spine behind the eye on this close-up. ![]() Another view of Oregonia gracilis rostrum. Note the postorbital spines. Photo by Dave Cowles, July 2000
Authors and Editors of Page: Dave Cowles (2005): Created original page |