Flat Spider Crab, Herbstia camptacantha

Flat Spider Crab, Herbstia camptacantha, Male. Crab provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, September 2009. Size: 3.0 cm (1.2 inches) x 3.0 cm (1.2 inches).

General Information: The Flat Spider Crab, Herbstia camptacantha, is a decapod brachyuran crab and a member of the Majidae Family, which includes the spider crabs that are also known as decorator crabs. They are known in Mexico as Mexicano cangrejo araña. Although first reported off the coast of Panama in 1893, the Flat Spider Crab was not reported in Mexican waters until 1979.

Identification:  The Flat Spider Crab are a brown in color with long legs and an oval-shaped body with a triangularly shaped carapace (shell) and covered with short spines. The legs have many heavily marginal spines and the chelipeds (claws) are long and thin. A key to identification is that the shell is nearly flat and the first walking legs are about the same as the second. The Flat Spider Crab has a maximum shell width of of 2.5 cm (1.0 inch).

Diet:  Like other spider crabs the Flat Spider Crab is an omnivore scavenger eating dead or decaying organisms as well as algae. due to spider crabs being very difficult to research the exact diet of the Flat Spider Crab is unknown.

Habitat and Range:  The Flat Spider Crab are found in all Mexican waters of the Pacific with the exception that they are absent from waters south of the state of Oaxaca along the coast of the mainland. They are a low intertidal species found around algae covered rocks at depths up to 61 m (200 feet). They are not commonly found inshore but are more common offshore and  subtidally.

Conservation Status:  From a conservation perspective the Flat Spider Crab has not been formally evaluated. However, they are common and of limited interest to most and should be considered to be of Least Concern.

Synonyms:  Fisheria depressa, Herbestiela camptacantha, and Mithrax sonorensis