''Placetron wosnessenskii'', common name the scaled crab, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of king crab found in most waters off

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

'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 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 tortoises, the unde ...

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-shaped organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through Neo-Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds ...

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 The Pribilof Islands (formerly the Northern Fur Seal Islands; , ) are a group of four volcanic islands off the coast of mainland Alaska, in the Bering Sea, about north of Unalaska and 200 miles (320 km) southwest of Cape Newenham. The ...

Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...

. In most instances it is found at depths of up to , but may also inhabit shallow intertidal areas.

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 star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

s as they have been witnessed feeding on the

echinoderms An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larv ...

. Few other

prey Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not ki ...

species have been observed but it can be 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 Pacific Ocean, North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of ...

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 (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

relationship with certain species of

sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...

. They may be found inhabiting areas containing ''

Metridium senile ''Metridium senile'', the Plumose, Fluffy, or Frilled anemone, is a species of sea anemone in the Family (biology), family Metridiidae. As a member of the genus ''Metridium'', it is a type of plumose anemone and is found in the seas off north-wes ...

'' and ''

Metridium farcimen ''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. ...

''.

References

External links

* {{Portal bar, Crustaceans, Marine life King crabs Crustaceans described in 1892 Crustaceans of the eastern Pacific Ocean Anomura of the Pacific Ocean Crustaceans of North America Monotypic decapod genera