Look Alikes
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How to Distinguish from Similar Species: Pagurus stevensae has a right cheliped more triangular than elongate and a double row of spines on the eminence near the midline of the dorsal surface of the propodus of the left chela, plus it has no white band on the end of the merus of its chelipeds. Pagurus kennerlyi has a white band on the merus of the chelae but its second antennae have alternating light and dark bands and it has a tuft of setae on the dorsal side of the base of its cornea.
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Comprehensive Description
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Biology/Natural History: This species is said to generally live symbiotically with the sponge Suberites latus or Suberites ficus, which dissolves and overgrows its shell. This specimen was in a "house" made largely or entirely of the hydroid Hydractinia milleri. This hydroid is said to encrust shells which have hermit crabs living in them, and eventually to overgrow the shell as the crab grows. The hermit crab frequently rubs the flagellae of its second antennae over the hydroid colony. In another Hydractinia-hermit crab symbiosis this behavior was found to result in the hermit crab gathering and eating some of the plankton the Hydractinia had captured. The presence of Hydractinia on a hermit crab seems to at least partially deter predation by octopus. Octopus usually readily capture hermit crabs and other crustaceans. However, an octopus clearly thinks twice about attacking a hermit crab with Hydractinia on its shell. Click here for a movie showing how octopus deal with Hydractinia-covered hermit crabs.
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Distribution
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Geographical Range: Bering Sea to Oregon; widespread but not abundant.
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Habitat
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Depth Range: Very low intertidal to 276 m
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Comprehensive Description
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This subtidal hermit crab, like most local hermit crabs has a smooth carapace which is only partly calcified and the bases of the eyescales are not covered by the carapace. The abdomen is curved. The carpus of the right cheliped is longer than wide and is not extremely flattened. The eyescales do not have a deep median furrow and they terminate in a single spine. The dactyls of legs 2 and 3 are not striped and are not obviously twisted in relation to the propodus. The dorsal surface of the palm of the left chela does not have a prominent ridge or crest near the midline. The ventral surface of the merus of the right cheliped does not have prominent tubercles. The left chela is more elongated than triangular, its carpus is longer than the merus, and there is a single row of large spines on the eminence near the dorsal surface of the propodus. The carpus of the right cheliped is about 1.5x as long as wide. The rostrum is pronounced and sharp tipped. There is a distinct white band on the distal parts of the merus of the chelipeds, which is the source of the animal's common name. The dorsal carapace has a network of white, tan, mahogany, and red with a red margin. The flagellum of the second antennae is reddish-brown with some white. There is no tuft of setae on the dorsal side of the base of the cornea.
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Habitat
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Gravel, sandy, or mud bottoms; symbiotic with sponges
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Pagurus dalli
provided by wikipedia EN
Pagurus dalli, commonly known as the whiteknee hermit, is a species of hermit crab in the family Paguridae.[4] It is found in the northeastern Pacific Ocean at depths down to about 276 m (900 ft). It usually lives in a mutualistic symbiosis with a sponge, or sometimes a hydroid.
Description
Pagurus dalli has a smooth, partially calcified carapace up to 1.8 cm (0.7 in) long, and a curved abdomen. The legs are light tan with white stripes, and it is the broad white band on the merus segment of the chelae (claws) that gives this hermit crab its common name. The dorsal surface of the carapace has a network of white, red, light and dark brown markings and is rimmed with red, and the flagellae (terminal segments) of the second pair of antennae are reddish-brown and white.[4]
Distribution
This hermit crab is native to the northeastern Pacific Ocean, its range extending from the Bering Sea to Oregon, but is not particularly common anywhere. Its depth range is from the low intertidal zone to a depth of about 276 m (900 ft), and it is found on sandy or muddy substrates or on gravel.[4]
Ecology
Like other hermit crabs, P. dalli uses an empty gastropod mollusc shell to protect its soft parts, primarily its abdomen. It usually lives symbiotically with a sponge such as Suberites ficus or Suberites latus, which overgrows and eventually dissolves the shell.[4] The sponge benefits from the crab's ability to move away from predators such as nudibranchs, while the crab may benefit from the sponge's unpalatability and the camouflage it provides.[5] P. dalli has been found enveloped in a similar way by the colonial hydroid Schuchertinia milleri. After the hydroid has dissolved the shell its semi-calcareous matted structure acts as a substitute. Being encrusted by a hydroid colony seems to deter predation by octopuses.[4]
Pagurus dalli is one of several species of hermit crabs in the infraorder Anomura that the parasitic barnacle Clistosaccus paguri uses as a host. A female cyprid larva of the parasite injects some cells into the crab's abdomen at any stage in the crab's moulting cycle. These develop internally sending out root-like growths into the host's tissues, and later developing an external, stalked protuberance housing the parasite's reproductive organs; its presence effectively castrates the host by causing the host's gonads to diminish in size.[6]
References
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^ Rathbun, Mary J. (1899). "List of Crustacea known to occur on and near the Pribilof Islands". In Jordan, D.S.; et al. (eds.). The fur seals and fur-seal islands of the North Pacific Ocean. Vol. 3. Washington: Government Printing Office. pp. 555–559. BHL page 36108694.
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^ Benedict, James E. (1892). "Preliminary descriptions of thirty-seven new species of hermit crabs of the genus Eupagurus in the U. S. National Museum". Proceedings of the United States National Museum. 15 (887): 1–26, 9. doi:10.5479/si.00963801.15-887.1. hdl:10088/13245. BHL page 15736863.
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^ McLaughlin, Patsy (2008). "Pagurus dalli (Benedict, 1892)". WoRMS. World Register of Marine Species. Retrieved 7 April 2019.
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^ a b c d e Cowles, Dave (2007). "Pagurus dalli (Benedict, 1892)". Invertebrates of the Salish Sea. Retrieved 7 April 2019.
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^ Bloom, Stephen A. (1975). "The motile escape response of a sessile prey: A sponge-scallop mutualism" (PDF). Journal of Experimental Marine Biology and Ecology. 17 (3): 311–321. doi:10.1016/0022-0981(75)90006-4. Archived from the original (PDF) on 2017-04-12.
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^ Tseng, James. "Clistosaccus paguri". Animal Diversity Web. Retrieved 7 April 2019.
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Pagurus dalli: Brief Summary
provided by wikipedia EN
Pagurus dalli, commonly known as the whiteknee hermit, is a species of hermit crab in the family Paguridae. It is found in the northeastern Pacific Ocean at depths down to about 276 m (900 ft). It usually lives in a mutualistic symbiosis with a sponge, or sometimes a hydroid.
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