The purple shore crab (''Hemigrapsus nudus'') is a common crab of the family

Varunidae The Varunidae are a family of thoracotrematan crabs. The delimitation of this family, part of the taxonomically confusing Grapsoidea, is undergoing revision. For a long time, they were placed at the rank of subfamily in the Grapsidae, but they a ...

. It can be found sheltering under rocks in inter-tidal areas along the west coast of North America, from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. This crab primarily eats

sea lettuce The sea lettuces comprise the genus ''Ulva'', a group of edible green algae that is widely distributed along the coasts of the world's oceans. The type species within the genus ''Ulva'' is ''Ulva lactuca'', ''lactuca'' being Latin for "lettuc ...

and other green algae, and occasionally scavenges dead animals.

Description

A small crab, ''H. nudus'' reaches sizes of approximately . Its

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

shell ( carapace) is generally a dark purple in color, although it may be olive green or red, with white or cream markings. The color of the legs matches the color of the carapace but the white-tipped claws ( chelipeds) are a lighter color with purple or red spots – these spots allow ''H. nudus'' to be distinguished from a similar looking crab, the lined shore crab, ''Pachygrapsus crassipes'', whose chelipeds lack spots. The legs of ''H. nudus'' lack

setae In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

, a distinguishing feature of the otherwise similar '' H. oregonensis''.

References

External links

* {{DEFAULTSORT:crab, shore, purple purple shore crab Crustaceans of the eastern Pacific Ocean Fauna of Alaska Fauna of Western Canada Fauna of the Western United States Fauna of the Baja California Peninsula Crustaceans described in 1851 Taxa named by James Dwight Dana