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 ap ...
. 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., ...
to
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 ...
in
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'', wikt:lactuca, ''lactuca'' being Latin ...
and other
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
, 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 co ...
shell (
carapace
A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...
) 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
Lining may refer to:
* Lining (sewing), the process of inserting an inner layer of fabric, fur, or other material
* Lining of paintings, the process of restoration paintings by attaching a new canvas to the back of the existing one
* Brake linin ...
, ''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. Th ...
, a distinguishing feature of the otherwise similar ''
H. oregonensis''.
References
External links
*
{{DEFAULTSORT:crab, shore, purple
purple shore crab
The purple shore crab (''Hemigrapsus nudus'') is a common crab of the family Varunidae. It can be found sheltering under rocks in inter-tidal areas along the west coast of North America, from Alaska to Baja California in Mexico. This crab primar ...
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