Slender decorator crab, graceful decorator crab, spider crab • Oregonia gracilis
Visible in one or more of the lower photos are curved hairs on the walking legs, and curved spines behind each eye. Both features distinguish the slender decorator crab from the longhorn decorator crab. The bottom right photo shows the differences in size, leg length, and decoration between decorator crabs (left) and kelp crabs (right). Photos by Gillian Harvey, Georgia Brander, and Julia Fisher.
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Identification
The carapace of the slender decorator crab is heart-shaped (also described as triangular or subtriangular) with a rostrum composed of two long, even, and parallel horns. Behind each eye is a large curved spine. Its carapace generally lacks other spines; it is instead covered in thin hooked setae to which the crab attaches pieces of algae, sponges, bryozoans, hydroids, and other growths. The crab's legs and claws also bear setae. This species tends to camouflage itself liberally with these "decorations" and so key identification characteristics may not always be readily visible. It's long, slender walking legs covered in hair (setae) are distinctive and may be more easily seen. Under the decorations the crab is a dully colour, usually grey or tan. The carapace reaches 4 cm wide.
See the E-Fauna and Rosario Beach Marine Laboratory species pages for more identification information.
Click here for a short video of a slender decorator crab.
Habitat & Range
This species is found in intertidal and subtidal zones to a depth of 435 m (1430 ft). It is most common in shallow habitats with mixed composition bottoms. Its range stretches from the Bering Sea to Monterey, California. It is also found in Japan.
Similar Species
The slender decorator crab can be confused with the less common longhorn decorator crab. Unlike the slender decorator, the longhorn decorator does not have curved spines behind its eyestalks, and its long walking legs are not covered in hooked setae. It has a spiny, pear-shaped carapace that may be undecorated or predominantly decorated with sponges or bryozoans, and its rostral horns are divergent rather than parallel.
The carapace of the slender decorator crab is heart-shaped (also described as triangular or subtriangular) with a rostrum composed of two long, even, and parallel horns. Behind each eye is a large curved spine. Its carapace generally lacks other spines; it is instead covered in thin hooked setae to which the crab attaches pieces of algae, sponges, bryozoans, hydroids, and other growths. The crab's legs and claws also bear setae. This species tends to camouflage itself liberally with these "decorations" and so key identification characteristics may not always be readily visible. It's long, slender walking legs covered in hair (setae) are distinctive and may be more easily seen. Under the decorations the crab is a dully colour, usually grey or tan. The carapace reaches 4 cm wide.
See the E-Fauna and Rosario Beach Marine Laboratory species pages for more identification information.
Click here for a short video of a slender decorator crab.
Habitat & Range
This species is found in intertidal and subtidal zones to a depth of 435 m (1430 ft). It is most common in shallow habitats with mixed composition bottoms. Its range stretches from the Bering Sea to Monterey, California. It is also found in Japan.
Similar Species
The slender decorator crab can be confused with the less common longhorn decorator crab. Unlike the slender decorator, the longhorn decorator does not have curved spines behind its eyestalks, and its long walking legs are not covered in hooked setae. It has a spiny, pear-shaped carapace that may be undecorated or predominantly decorated with sponges or bryozoans, and its rostral horns are divergent rather than parallel.
Intriguing Info This crab decorates itself the most of all northern decorator crabs. See this Friday Harbour Labs post for further information on this process. The video at right shows a decorator crab busy decorating. Adult males and adult females can differ significantly in appearance, and were once thought to be separate species. See the E-Fauna page for this species for more information |
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References
Cowles, D. (2005). Oregonia gracilis Dana, 1851. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/04/2014.
Harbo, R.M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 76.
Hart, J. (1984). Oregonia gracilis Dana, 1851. In Klinkenberg, Brian. (Editor) 2012. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 01/04/2014.
Jensen, G.C. (1995). Pacific Coast Crabs and Shrimp. Monterey, CA: Sea Challengers. P. 23.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).
Cowles, D. (2005). Oregonia gracilis Dana, 1851. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 01/04/2014.
Harbo, R.M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 76.
Hart, J. (1984). Oregonia gracilis Dana, 1851. In Klinkenberg, Brian. (Editor) 2012. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 01/04/2014.
Jensen, G.C. (1995). Pacific Coast Crabs and Shrimp. Monterey, CA: Sea Challengers. P. 23.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).