Tuna Crab

Grimothea planipes

The Tuna Crab, also known as Grimothea planipes, is a bright red crustacean that can grow up to 13 centimeters long. It resembles a true lobster but is distinguished by its shorter abdomen. This species inhabits the eastern Pacific Ocean, primarily along the continental shelf west of Mexico. It is typically found south-west of San Diego, but during warmer years, its range can extend northwards into California, often signaling an El Niño event. The Tuna Crab is pelagic and can be found at depths ranging from 101 to 310 meters, though it is often observed in shallower waters. Tuna Crabs are omnivorous, feeding on protists, zooplankton, and diatoms. They are known to filter-feed on blooms of phytoplankton and zooplankton. This species plays a crucial ecological role by converting primary production into energy for larger marine organisms. They are also preyed upon by sea otters and certain seabirds, especially during El Niño years when they are washed ashore in large numbers. Reproduction in Tuna Crabs involves a precopulatory courtship ritual, and they typically engage in indirect sperm transfer. The species has a unique life cycle where the planktonic larvae are carried out to sea by the California Current but return to the continental shelf using an opposing undercurrent. Despite their ecological significance, Tuna Crabs have not been evaluated for conservation status by the IUCN.