About Pugettia richii Dana, 1851
Pugettia richii Dana, 1851 typically reaches 3–4 cm (1.2–1.6 in) in size. It has one sharp lateral tooth that protrudes from the front of its exoskeleton. Its carapace is usually red; the chelae are bright blue near the tip, with tips that can be orange, white, or red. This small, hard-to-locate crab lives on kelp and benthic algal mats. In a study of five spider crab species in a California coastal kelp forest, Pugettia richii was found to be the most abundant of the group, which also included Loxorhynchus crispatus, Pugettia producta, Mimulus foliatus, and Scyra acutifrons. This species occurs in the rocky intertidal zone ranging from Alaska to northern Mexico. It is abundant in kelp forests and on rocky reefs, and climbs kelp during the night. Populations can reach 300 to 2,100 crabs per single kelp plant, with the highest counts occurring at night. Males are usually found higher up on kelp plants, while females remain near the base of the plants. Larvae of P. richii are very abundant off the coast of California, and were present in 88.5% of collected plankton samples. The species is most commonly found on the algae Cystoseira and within coralline algal mats.
