''Cryptolithodes typicus'', often referred to as the butterfly crab or the turtle crab,
is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
lithodid crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...
native to coastal regions of the northeastern Pacific Ocean, ranging from
Amchitka Island
Amchitka (; ale, Amchixtax̂; russian: Амчитка) is a volcanic, tectonically unstable and uninhabited
island in the Rat Islands group of the Aleutian Islands in southwest Alaska. It is part of the Alaska Maritime National Wildlife Re ...
, Alaska to
Santa Rosa Island, California.
Appearance
The crab's
butterfly
Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprise ...
-shaped
carapace has a stone-like camouflage, which it uses to blend in against the rocks of the
subtidal
The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth.
From the point of view of marine biology it forms a relatively stable and well-illuminated ...
and
low intertidal zones.
Carapace color within the species varies greatly, but small individuals (< in length) are typically white, while larger ones tend to have an assortment of vibrant colors.
The carapace is exceptionally broad and completely hides the appendages when viewed from above or from the side; it has a median raised crest which is often a different color that contrasts with other parts. The male carapace is at its widest at a point further back than that of the female. The
cheliped
A chela ()also called a claw, nipper, or pinceris a pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds. ...
s of the male are relatively larger than the widest point of the female. The right claw is larger than the left and both claws are sharp, curved, and stout. Each segment of the walking legs has a dorsal crest.
Habitat
The butterfly crab resides on rocks within the subtidal and low intertidal zones.
When its intertidal habitat is exposed to the atmosphere during extreme low
tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide tables ...
, it can be found clinging to the substratum in rock crevices or at the base of the seagrass ''
Phyllospadix
''Phyllospadix'', surfgrass, is a genus of seagrass, a flowering plant in the family Zosteraceae, described as a genus in 1840. ''Phyllospadix'' grows in marine waters along the coasts of the temperate North Pacific.
It is one of the seagras ...
''.
It has been found to a depth of .
Etymology
The genus name "''Cryptolithodes''" means "hidden stone",
while its species name "''typicus''" denotes it as the genus'
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...
. The nickname "butterfly crab" is derived from the crab's carapace, which resembles a butterfly, and the nickname "turtle crab" derives from the way its carapace covers its appendages from above and the sides.
See also
*''
Cryptolithodes sitchensis'', the umbrella crab
*''
Cryptolithodes expansus''
*
Intertidal ecology
Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study th ...
References
Further reading
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External links
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{{Taxonbar, from=Q3932595
King crabs
Crustaceans of the eastern Pacific Ocean
Crustaceans described in 1849
Taxa named by Johann Friedrich von Brandt