The reproductive behaviour of α-, β-, and γ-male morphs in Paracerceis sculpta, a marine isopod crustacean

As studied in the Gulf of California, alpha-males are largest in body size and defend breeding sites in intertidal sponges. Beta-males are smaller and resemble sexually receptive females in behaviour and body form. Gamma-males are tiny and are capable of rapid movements. Resident and intruder α-males used their walking legs, uropods and body positioning to retain or gain access to breeding sites. Intruders were consistently more aggressive than residents in contests, except when breeding sites containing sexually receptive females were limited. Despite their relative quiescence, residents retained their spongocoels in most contests, apparently due to the positional advantage residents gain when situated in the spongocoel. When interacting with α-males, β-males imitated female courtship behaviour, and α-males responded as if β-males were females. Tactile stimulation of α-males by β-males may thus be sufficient to release normal α-male courtship behaviour. -from Author