Coldwater Mole Crab, Emerita analoga

Coldwater Mole Crab, Emerita analoga. Collected by hand off the beach in the greater San Diego, California area, August 2004. Size: 3.1 cm (1.2 inches) x 2.1 cm (0.8 inches).

General information: The Coldwater Mole Crab, Emerita analoga, is one of four Mole Crabs found in Mexican waters, all belonging to the Hippidae Family that are known in Mexico as muy-muy cochitos. They are also known as the Pacific Sand Crab and in Mexico as muy-muy limanche. The Hippidae family is comprised of Emerita Genus, which has twelve global members, and the Hippa Genus, which has fifteen global members. These crabs are completely harmless lacking the ability to bite or pinch, making them a favorite bait for shore fisherman.

Identification: Members of the Emerita Genus have a strongly convex oval shell or carapace that covers the legs, front legs without claws (nonchelated) and back legs (telson) that resemble paddles, long slender antenna and long slender eye stalks. Members of the Hippa Genus have a similar carapace, but front (nonchelated) and back legs that are slender and pointed, short stubby antenna and short stubby eye stalks. The Coldwater Mole Crabs are characterized by striations that run across the back half of their shells, their short paddle-like feet and short antennae and eyestalks. They reach a maximum length of 2.5 cm (1.0 inch) with females being about 30% larger than males. They can be easily confused with the Pacific Mole Crab, Hippa pacifica (differently shaped feet), the Striated Mole Crab, Hippa strigillata (different shaped feet and lines along the margins of the carapace) and the Tropical Mole Crab, Emerita rathbunae (lines completely covering the carapace).

Habitat and Range: The Coldwater Mole Crab is a very common species that is found along the northwest coast of Baja southward to Guerrero Negro and in the middle third of the Sea of Cortez. They are found within shifting sand on wave-swept beaches in areas washed by waves collecting debris that passes by. They bury themselves near the surface, facing seaward, with only their antennae and eyes out of the sand. 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. The Coldwater Mole Crabs are characterized by striations that run across the back half of their shells, their short paddle-like feet and short antennae and eyestalks. They reach a maximum length of 2.5 cm (1.0 inch) with females being about 30% larger than males. They can be easily confused with the Pacific Mole Crab, Hippa pacifica (differently shaped feet), the Striated Mole Crab, Hippa strigillata (different shaped feet and lines along the margins of the carapace) and the Tropical Mole Crab, Emerita rathbunae (lines covering the carapace completely).

Diet and Reproduction: The Coldwater Mole Crabs collect floating debris from wave draining off the beach with their first pair of legs, then transferring food to their mouths. They primarily eat plankton and any other small organisms and have even been recorded to eat the tentacles of the Man O’ War jellyfish.  Interestingly they reproduce based on food availability and not on tidal or water temperature changes.

Conservation Status:  From a conservation perspective the Coldwater Mole  Crab has not been formally evaluated. However, they are common regionally with a wide distribution and of limited interest to most and should be considered to be of Least Concern. They are commonly encountered along the beaches of San Diego, California. They are small in stature and are of limited interest to most other than they are utilized as a quality bait by surf fishermen.