Flattop Crab

Animal Unique | Flattop Crab | Flattop Crab is a small crab with a shell reaches a diameter of only about ¾ inch. The shield is round and compared to other crabs, the claws seem huge compared to the rest of the crab. If the claws are opened, you can see that the base of the movable "finger" has a bruise. Flattop Crab is a kind of marine porcelain crab found in the eastern Pacific. It is a filter feeder, and also wipe food from rocks. This crab is found along the coast and at a depth of 90 meters on the west coast of North America from California to Alaska. It prefers areas with strong currents and can be found under rocks, especially those embedded in gravel or sand under seaweed and mussel beds in both exposed and sheltered shores.

Scientific classification
Kingdom:     Animalia
Phylum:     Arthropoda
Subphylum:     Crustacea
Class:     Malacostraca
Order:     Decapoda
Infraorder:     Anomura
Family:     Porcellanidae
Genus:     Petrolisthes
Species:     P. eriomerus

Flattop Crabs differs from the true crabs in having four instead of five pereiopods limbs or walk normally visible and are more akin to king crabs and hermit crabs. This little Flattop Crab has a carapace up to 20 millimeters wide with a rounded outline. The body, legs and claws are dorsally flattened. There are a couple of long antennae just off the eyes. The large claw-bearing carpi of the chelipeds have parallel sides and two times as long as they are wide. The limbs are covered with tufts of setae that are most noticeable when the animal is underwater. This porcelain crab is predominantly red-brown or bluish-gray, but the palps, a part of the mouth parts and the knuckles of the cheliped dactyls are blue.

Flattop Crab is a filter feeder eriomerus surviving largely on diatoms that collect the setae on its mouthparts. It also uses the tufts of setae on its chelipeds on deposits by wiping the surfaces of rocks for consumption. Females usually have two broods a year. The larvae are free living and are part of the zooplankton. The zoeal larval stage has a characteristic long rostrum. Men, women and some young people can come together in small groups, and in this, only the dominant males are likely to mate. 

 

Flattop Crabs are not true crabs, but belong to a group called anomurans, making them more akin to crabs and hermit crabs king. An easy to distinguish between perceived and real cabins anomurans is that in anomurans, normally only four pairs of legs are visible, where as in real crabs, five pairs can be seen.

Like other porcelain crabs, Flattop Crab sometimes throws off limbs as a distraction when trying to escape a predator, a process known as autotomy. In this species, however, the claws of the cast limb grip still strong after the divorce. The part is regrown by the porcelain crab over the period of several molts.

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