Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata

We studied the reproductive behaviour of the blue-ringed octopus, Hapalochl aena lunulata, in the laboratory by examining 15 male-male and nine male-fe male interactions. The initiation of physical contact was independent of se x, size or residency status, and there were no noticeable changes in behavi our such as sexual displays associated with courtship or aggression prior t o contact. Males did not distinguish between females or other males and cop ulated (defined as the insertion of the hectocotylus into the mantle cavity of another octopus) readily with both. Spermatophores were released in all copulations with females but not with males. The duration of copulation wa s significantly longer in male-female interactions (median 160.5 min) than in male-male interactions (median 30 s). Although male-male copulations end ed passively with the withdrawal of the hectocotylus by the initiating anim al, male-female copulations were always terminated by the females following an intense struggle. These studies suggest the inability of male H. lunula ta to determine the sexual identity of potential mates prior to the inserti on of the hectocotylus and demonstrate the active role of the female during copulation. (C) 2000 The Association for the Study of Animal Behaviour.