Identification Photos: Panamic Spider Crab, Maiopsis panamensis: The Panamic Spider Crab is a bright red decapod with very long legs and an oval-shaped body. It has eyes on short stalks, a broad flattened carapace (shell), a small abdomen folded under the thorax, and long arms with big pincers.

The Panamic Spider Crab is the largest of the brachyuran crabs with a shell that approaches 10 inches and “wing spans” that approach 4.5 feet! The larger males, up to 8.5 pounds in weight, are more abundant than the females, which grow up to 3 pounds.

The Panamic Spider Crab has been collected at depths between 50 feet and 1,000 feet in the water column over a variety of substrate. Reproduction occurs during November and December. The eggs are incubated via attachment to the female abdomen from spawning to hatching.

The Panamic Spider Crab ranges from Topolobampo, Sinola, Mexico, to Caleta La Cruz, Peru. Shrimp haulers make the majority of spider crab collections as a by-catch. The Panamic Spider Crab can be confused with the much smaller (about one-third of the size) Velvet Spider Crab, Stenocionops ovata, with possibly very large populations living in the northern Sea of Cortez.

The Panamic Spider Crab is a brachyuran crab and a member of the Majidae Family, which includes the spider crabs that are known in Mexico as cangrejos. There are 60 different crabs that live in the Sea of Cortez, the majority of which have shells (carapaces) of less than one inch. The small crabs are found in rocky, intertidal or shallow subtidal environments where they crawl among algae. They are also found in tidal pools. In contrast, spider crabs live in deep water on the continental shelf. They are not well known and rarely studied. Although first reported off the coast of Panama in 1893, the Panamic Spider Crab was not reported in Mexican waters until 1979.

Panamic Spider Crab, Maiopsis panamensis: A rare beach collection made in June 2007 at the commercial fishing beach near Todos Santos, Baja California Sur, Mexico, at 23.24.88 degrees north and 110.13.88 degrees west, documenting a possible range extension for this species. Size approximately 30 cm (12 inches). Note: We are not aware of any quality photos of an intact Panamic Spider Crab. Identification courtesy of Dr. Michel E. Hendrickx, Unidad Academica Mazatlan. Description and photo courtesy of John Snow.