Pacific Mole Crab, Hippa marmorata

Pacific Mole Crab, Hippa pacifica. Collected by hand off the beach at Cabo Real, Km 21, Baja California Sur, August 2004. Size 3.0 cm (1.2 inches) x 2.1 cm (0.8 cm).

General information: The Pacific Mole Crab, Hippa pacifica, is one of four Mole Crabs found in Mexican waters, all belonging to the Hippidae Family of mole crabs that are known in Mexico as muy-muy cochitos. In Mexico the Pacific Mole Crab is known as cochito del Pacifico. The Hippidae family is comprised of Emerita Genus and the Hippa Genus. They adapt to conditions of heavy surf and strong currents. In some places they are fairly abundant but difficult to observe because they blend into the background extremely well. Interestingly they reproduce based on food availability and not on seasonal, tidal or water temperature changes. Although hard to catch they are a favorite live bait of the Southern California surf fisherman but not utilized often as bait in Mexico.

Identification: Members of the Emerita Genus have a strongly convex oval shell or carapace that covers the legs. The front legs are without claws (nonchelated) and the back legs (telson) resemble paddles. They have long slender antenna and long slender eye stalks. Members of the Hippa Genus have a similar carapace, but the front (nonchelated) and back legs that are slender and pointed. They have short stubby antenna and short stubby eye stalks.

The Pacific Mole Crab are characterized by having an absence of striations that run across the back half of their shells, their long pointed feet, and long antennae and eyestalks. They also have two small lobes at the top of the shell between the eyes that aid in differentiating this species. They reach a maximum of just over 2.5 cm (1.0 inch) in length. They can be easily confused with the Coldwater Mole Crab, Emerita analoga (differently shaped feet and lines across the back half of the carapace), the Marmorata Mole Crab, Hippa marmorata (differently shaped feet and lines along the margins of the carapace) and the Tropical Mole Crab, Emerita rathbunae (lines covering the carapace completely).

Habitat and Range: The Pacific Mole Crab is found along the shoreline on the West Coast of the Baja, south of La Paz on the east cost of the Baja, along the coast of the mainland from Acapulco south to Guatemala and around all oceanic islands. The Mole Crabs reside buried in sifting sand on wave-swept beaches in areas washed by waves burying themselves near the surface, facing seaward, with only their antennae and eyes out of the sand. They are hard to see due to their cryptic coloration and being buried in sand but then are visible when moving between waves.

Diet: The Pacific Mole Crab collect floating debris from waves draining off the beach with their first pair of legs that transfer food to their mouths.

Conservation Status: The Pacific Mole has not been formally evaluated from a conservation prospectus.  However, they are common and of limited interest to most and should be considered to be of Least Concern.

Synonyms: Cancer arnoldorum, Hippa pacifica, Remipes marmoratus, and Remipes pacificus.