Helmet crab • Telmessus cheiragonus
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Helmet crabs photographed by Tristan Blaine (top), Nathaniel Glickman (bottom left), and Alanah Nasadyk (bottom middle). Bottom right photo, by Kelly Fretwell, shows a helmet crab carapace. Note the stiff setae and six teeth cutting into the edge of the carapace below the right eye.
Identification
The helmet crab is covered in stiff club-shaped hairs (setae), and is usually a yellow-green colour with red, brown, or orange patches. The carapace margin is lined with red, brown, or orange as well - this colour accentuates the six large teeth that cut into both sides of the carapace. This is particularly visible in the left-hand photo above. The carapace reaches 10 cm across. This crab doesn't have a rostrum; instead there are four small teeth between its eyes.
Habitat & Range
This crab buries itself in sediment and hides in eelgrass or kelp beds. It is mostly subtidal, though it is found in intertidal and subtidal zones to a depth of 110 m. It is most often found in soft-bottomed habitats, and occasionally may occur in rocky-bottomed areas. Its coastal North America range stretches from the Bering Sea to Monterey, California, and is most common north of Oregon. It is also found in coastal areas of Siberia, Japan, and Korea.
Similar Species
The helmet crab is sometimes misidentified as the green crab (Carcinus maenus), an invasive species that threatens shellfish and other crab species. The green crab has a smooth body whereas the helmet crab is covered in setae.
Intriguing Info
The helmet crab can be difficult to pick out among kelp, eelgrass, and sediment due to its camouflaging colours. It is one of the fastest-moving crabs found along the BC coast.
iNaturalist
https://www.inaturalist.org/taxa/180391-Telmessus-cheiragonus
The helmet crab is covered in stiff club-shaped hairs (setae), and is usually a yellow-green colour with red, brown, or orange patches. The carapace margin is lined with red, brown, or orange as well - this colour accentuates the six large teeth that cut into both sides of the carapace. This is particularly visible in the left-hand photo above. The carapace reaches 10 cm across. This crab doesn't have a rostrum; instead there are four small teeth between its eyes.
Habitat & Range
This crab buries itself in sediment and hides in eelgrass or kelp beds. It is mostly subtidal, though it is found in intertidal and subtidal zones to a depth of 110 m. It is most often found in soft-bottomed habitats, and occasionally may occur in rocky-bottomed areas. Its coastal North America range stretches from the Bering Sea to Monterey, California, and is most common north of Oregon. It is also found in coastal areas of Siberia, Japan, and Korea.
Similar Species
The helmet crab is sometimes misidentified as the green crab (Carcinus maenus), an invasive species that threatens shellfish and other crab species. The green crab has a smooth body whereas the helmet crab is covered in setae.
Intriguing Info
The helmet crab can be difficult to pick out among kelp, eelgrass, and sediment due to its camouflaging colours. It is one of the fastest-moving crabs found along the BC coast.
iNaturalist
https://www.inaturalist.org/taxa/180391-Telmessus-cheiragonus
References
Cowles, D. (2005). Telmessus cheiragonus (Tilesius, 1812 or 1815). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 07/04/2014.
Harbo, R.M. (2011). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 106.
Hart, J. (1984). Telmessus cheiragonus (Tilesius, 1815). 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 07/04/2014.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 302.
Jensen, G.C. (1995). Pacific Coast Crabs and Shrimp. Monterey, CA: Sea Challengers. P. 20.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).
Cowles, D. (2005). Telmessus cheiragonus (Tilesius, 1812 or 1815). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 07/04/2014.
Harbo, R.M. (2011). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 106.
Hart, J. (1984). Telmessus cheiragonus (Tilesius, 1815). 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 07/04/2014.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 302.
Jensen, G.C. (1995). Pacific Coast Crabs and Shrimp. Monterey, CA: Sea Challengers. P. 20.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).
