Spinyback Spider Crab

Libinia spinosa is a member of the crab superfamily Majoidea which are commonly known as the spider crabs. The carapaces of this organism can measure up to 89 mm and its leg span can be up to 568 mm. The number of median spines of Libinia spinosa can vary, with 7 being the most common number, but Libinia spinosa with 5, 8, and 10 median spines are also seen commonly. Testes are visibly flat, transparent structures that are coiled anteriorly.

Libinia spinosa is commonly found at both mud and sand bottoms in the Southwestern Atlantic and Pacific oceans. It inhabits Southwestern Atlantic waters ranging from Nova Scotia to Argentina. In the Pacific Ocean, it is found off the coasts of the United States, Baja California, Galápagos Islands, Hawaii, Peru, and Chile. The depths at which this organism is found at range from the intertidal zone to 170 m. It prefers sediment that contains both silt and clay.

Libinia spinosa engage in precopulatory courting using both olfactory and tactile cues, indirect sperm transfer is common. Females have been shown to exhibit sexual selection with their preference for larger males. The trait that has been shown to be most highly correlated with mate acquisition for males is large cheliped size. Males have been shown to exhibit mate guarding where they will maneuver their chelipeds around the female and fight off other males. Precopulatory mate guarding is exhibited significantly longer than postcopulatory mate guarding. Males breed with females by turning the female upside down and below them and subsequently inserting their gonopods into the female's gonophores. Male copulatory organs consist of a long first gonopod and a short stout second gonopod. Females produce 1-3 offspring for each breeding season.