Little is known about the reproductive habits of deep-living squids. Using remotely operated vehicles in the deep waters of the Monterey Submarine Canyon, scientists from the Monterey Bay Aquarium Research Institute and University of Rhode Island have found evidence of mating on similar body locations in males and females of the rarely seen mesopelagic squid Octopoteuthis deletron.

In a study published today in Biology Letters, male squid were found to routinely and indiscriminately mate with both males and females.

Most squid species are short-lived and promiscuous, with a single, brief reproductive period. In the deep, dark habitat where O. deletron lives, potential mates are few and far between. The researchers suggest that same-sex mating behaviour by O. deletron is part of a reproductive strategy that maximizes success by inducing males to indiscriminately and swiftly inseminate every same species squid that they encounter.

Direct observations of mating behaviour of deep-sea squid are restricted to a single observation of a possible mating event. Using remotely operated vehicles (ROVs) for exploration and research, has shed new light on our knowledge of deep-sea squid behaviour.

Males of the genus Octopoteuthis deposit spermatophores, complex structures containing millions of sperm, on the female. Here they discharge sperm-containing sacs called spermatangia that implant into the female’s tissue. Empty spermatangia remain attached to a female’s body and provide evidence of recent mating.

Same sex mating behaviour in marine invertebrates is very poorly known, although it has been reported before in cephalopods.

Mating in O. deletron, as in many other squids, is probably rapid, as spermatophores are quickly passed between partners and spermatangia release follows soon thereafter. Mature males and maturing mated females of O. deletron are of the same size, solitary and have only minor morphological differences. The combination of a solitary life, poor sex differentiation, the difficulty of locating a squid of the same species and the rapidity of the sexual encounter probably results in the observed high frequency of spermatangia-bearing males in this species. Apparently, the costs involved in losing sperm to another male are smaller than the costs of developing sex discrimination and courtship, or of not mating at all. This behaviour further exemplifies the ‘live fast and die young’ life strategy of many cephalopods

Further Reading:
Hendrik J. T. Hoving, Stephanie L. Bush, and Bruce H. Robison
A shot in the dark: same-sex sexual behaviour in a deep-sea squid
Biol Lett 2011 : rsbl.2011.0680v1-rsbl20110680.