Placetron wosnessenskii Schalfeew 1892

Vertical rock faces and overhangs associated with Metridium senile or Metridium giganteum, among boulders.

Geographical Range: Pribilof Islands to Puget Sound

Depth Range: Shallow subtidal to 110 m

This lithodid crab has a wide, mostly soft abdomen, which is not held as tightly against the underside of the thorax as some other species do. The chelae are spoon-shaped and have setae along the edges; both are of similar size. The carapace and legs are covered with what looks like scales. Colored greenish gray to reddish dorsally, lighter underneath. Walking legs may have some banding and yellow or orange near the tips. Carapace width to 7.2 cm.

How to Distinguish from Similar Species: At first glance this crab looks superficially like the helmet crab Telmessus cheiragonus or even like the shield-back kelp crab Pugettia producta, but can be distinguished by the wide, soft abdomen, the scale-like appearance, and the modified 5th leg characteristic of Anomurans.

Biology/Natural History: Have been observed eating brittle stars. Predators of this species include river otter. The abdomen of the female is mostly covered with plates; that of the male is soft with vestigial plates. We have sometimes observed this crab sheltering under the anemone Cribrinopsis fernaldi.