Helmet Crab

Telmessus cheiragonus

The Helmet Crab, known scientifically as Telmessus cheiragonus, is a member of the family Cheiragonidae. This species is typically found in temperate to polar regions, specifically in the Eastern Pacific and Arctic areas, including the coastal waters of Alaska, USA, and Canada. Divers can encounter this crab on rocky and sandy bottoms, ranging from the low intertidal zones to depths of up to 39 meters. Helmet Crabs can grow to a maximum length of 10 cm across the carapace. Their appearance is characterized by a robust and somewhat rounded shell, which resembles a helmet, hence the common name. This species is part of the order Decapoda, which are mostly gonochoric, meaning they have distinct male and female individuals. The crabs engage in a precopulatory courtship ritual, utilizing both olfactory and tactile cues, and typically transfer sperm indirectly. While the Helmet Crab is a species to observe, its conservation status has not been evaluated by the IUCN. Divers encountering this species may find it on the ocean floor, where it blends into its environment, making it a unique sight during a dive.