If this the right species?
Maybe from a blue crab?
Is this a blue crab?
Amazing seafood in local fish market in Valdivia (Chile). Here some crabs called "jaivas".
Isopod on abdomen.
See comment here:
Baby crab found on Texas A&M Corpus Christi University Beach (Ward Island)
Crab found in Packery Channel, Padre Island, Tx
Malacostraca is the largest of the six classes of crustaceans, containing over 25,000 extant species, divided among 16 orders. Its members display a greater diversity of body forms than any other class of animals, and include crabs, lobsters, shrimp, krill, woodlice, scuds (Amphipoda), mantis shrimp and many other less familiar animals. They are abundant in all marine environments and have also colonised freshwater and terrestrial habitats. They are united by a common Bauplan, comprising 20 body...