Mexican Spider Crab, Libinia mexicana

Mexican Spider Crab, Libinia mexicana. Provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, September 2009. Size: 3.3 cm (1.3 inches) x 2.5 cm (1.0 inch). Identification courtesy of Dr. Richard Brusca, Tucson, Arizona.

General information: The Mexican Spider Crab, Libinia mexicana, is a brachyuran crab and a member of the Majidae Family, which includes the spider crabs that are known in Mexico as cangrejos. It is known locally as cangrejo araña de Mexicana. Spider crabs are rarely studied and not much is known about their reproduction, behavior, or diet.

Identification: The Mexican Spider Crab is an odd looking crab with an inflated oval carapace (shell) and a long tubular rostrum (snout). The shells range from 5.0 cm (2.0 inches) to 6.5 cm (2.5 inches) in length and bear short brown hairs (pubescence) with six dorsal spines in a row down the middle of the back plus several other spines on both sides of the median row. The claws (chelae) are white and much longer than the first walking legs which in turn are longer than the second pair.

Habitat and Range: The Mexican Spider Crab is a low intertidal species found at depths up to 50 m (164 feet) in an around algae covered rocky rocks. They are a frequent by-catch of shrimp trawlers. They have a limited range being found only throughout the Sea of Cortez.  The collection photographed below was made off the southwest coast of Baja documenting a possible range extension for this species.

Diet:  The diet of the Mexican Spider Crab is unknown but most likely as a deep water dwelling crab most likely they scavenging the bottom floor for decaying organisms, other small invertebrates and algae.

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