Mouthless Land Crab, Cardisoma crassum

Mouthless Crab, Cardisoma crassum. Photographs taken just west of the Puerto Los Cabos Marina, Baja California Sur, August 2020. Size: 10 cm (3.9 inches). Photographs and identification courtesy of Robert North.

Mouthless Land Crab, Cardisoma crassum. Crab collected within the confines of the San José River Estuary, Los Cabos, Baja California Sur, September 2012. Size: 3.3 cm (1.3 inches) x 2.8 cm (1.1 inches).

General information: The Mouthless Land Crab, Cardisoma crassum, also known as the Giant Land Crab and in Mexico as cangrejo azul, cangrejo terrestre gigante, cangrejo terrestre sin boca and moro sin boca, is a member of the Gecarcinidae Family of land or terrestrial crabs. There are twenty-one family members that have been placed in six genera. Reproduction involves external fertilization with each female producing between 175,000 and 850,000 eggs in annual cycles. The females return to the sea to release their larvae, where they develop and then return to land as magalops.

Identification: The Mouthless Land Crab is a mid to large-sized crab that is characterized by having an oval thick, inflated shell that is wider than it is deep and one claw (chelae) that is larger than the other. They have a wide forehead with eyes on stalks that are set near the sides of the body. Mouthless Crabs have a purplish-blue shell, red legs and whitish pincers. The juveniles are more highly colored than the adults. The males are brighter in color than the females. Their shells are covered with hair. A key to identification is a pair of small pointed triangularly shaped teeth at the top of the shell between the origin of the eye stalk and the primary claw. Otherwise the shell is without teeth. They have a strong triangular shaped pointed spine at the upper corners of the shell and their carpi have strong spines. They possess a series of gills and the shell covering the gills has blood vessels that can extract oxygen from the air. The females normally outnumber males by a ratio of three to two. Their shells reach a maximum of 13.2 cm (5.2 inches) in width and 300 g (11 ounces) in weight. The females and males are of similar size and easily differentiated via the clear differences in the ventral sides.

Habitat and Range: The Mouthless Land Crab resides in coastal environments that may include brackish water, estuaries, and mangroves within fresh water river basins adjacent to salt marshes as they require access to the sea for breeding and larval development. They reside in burrows with multiple entrances that they build in dry mud within plant roots, including mangroves; they are also found around rocky crevices. The Mouthless Crab is a resident of Mexican coastal areas of the Pacific Ocean ranging from Todos Santos, to Loreto, Baja California Sur southward along the southeast coast of Baja, and from Los Mochis, Sinaloa southward along the coast of the mainland to Guatemala.

Diet: The Mouthless Land Crab is an omnivore that consumes plant materials and on occasion, dead animal matter.

Conservation Status: The Mouthless Land 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. They are an important food source in southern Mexico. They are caught by hand and sold fresh in local markets. They are subject to a high level of illegal commercial exploitation, including their utilization by the pet trade due to their attractive colors. They are also an important food source for alligators, birds and raccoons.

Synonym:  Cardiosoma latimanus