''Placetron wosnessenskii'', common name the scaled crab, is a
species of
king crab found in most waters off
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
's west coast. It is the
only species in the genus ''Placetron''.
Description
Major characteristics include a soft leathery abdomen, a wide
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 ...
narrowing at the anterior end much like a trapezoid, similar shaped chelae, and coloration ranging from a clouded green to reddish sometimes with banding along the legs.
The name of this decapod is derived from the scale like pattern that covers its legs and partially covers its carapace. The odd structure of the
chelae
A chela ()also called a claw, nipper, or pinceris a pincer (biology), 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 ...
which are spoon-like in nature and are largely covered in setae.
Range and habitat
The scaled crab is found in waters ranging from
Pribilof Islands to
Puget Sound.
In most instances it is found at depths of up to , but may also inhabit shallow intertidal areas.
Possible areas on habitation include rocky substrates either near drop offs or among boulders.
Biology
The carapace width has been measured in size from . Being a lithode crab it has an asymmetrical body.
Diet of the scaled crab is known to include
brittle stars as they have been witnessed feeding on the
echinoderms
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...
. Few other
prey species have been observed but it can assumed that other food sources are similar to those of similar crab species. The crab themselves are prey to the
sea otter
The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of the weasel family, but among the small ...
and presumably other large predators. Females and males differ in the structure of their abdomen. The female's abdomen is covered in plates whereas the male's is covered in vestigial plates. These plates give the male a rubbery look and feel to their abdomens.
Many have been observed to have a
symbiotic
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
relationship with certain species of
sea anemone
Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...
. They may be found inhabiting areas containing ''
Metridium senile'' and ''
Metridium giganteum
''Metridium farcimen'' is a species of sea anemone in the family Metridiidae. It is commonly known as the giant plumose anemone or white-plumed anemone. It is found in the eastern Pacific Ocean from Alaska down to Catalina Island, California.
...
''.
Similar species
Quick inspection of the scaled crab can lead to confusion since at a glance the crab can resemble the helmet crab, ''
Telmessus cheiragonus'', in many ways. The two though can be easily told apart by the scaled crabs soft abdomen and characteristic pattern of scales.
References
{{Taxonbar, from=Q3934140
King crabs
Crustaceans of the eastern Pacific Ocean
Monotypic arthropod genera