RAUNCHY video footage from the depths of the Pacific Ocean has got marine

biologists excited – and perplexed. For the first time, they have witnessed

two deep-sea octopuses having sex – only to discover they have been watching

the intimate embraces of two males of different species. “If you’re going to

see one, and only one, act of mating behaviour between deep-sea octopuses, you

would not expect to see this,” says Janet Voight, assistant curator of

invertebrates at the Field Museum of Natural History in Chicago.

The octopuses were caught in the act by marine biologist Richard Lutz of

Rutgers University in New Brunswick. Last December, the deep-sea submersible

Alvin ventured 2512 metres below sea level to the East Pacific Rise, where it

encountered the two octopuses and filmed 16 minutes of torrid footage.

Voight, an octopus expert, was called in to study the video recording. She

immediately noticed that both octopuses had a specialised arm characteristic

of males – with a groove along its length and a cup-shaped grasper at its tip.

During mating, the male uses the groove to squeeze a protein packet filled

with sperm down toward the grasper, which then grabs the sperm packet and

deposits it in the female’s oviduct, inside her body cavity.

In the video, the smaller octopus – a white-coloured species unknown to

science – was sitting on top of a larger, brown one, also unidentified. The

smaller octopus was rubbing its sexual arm along its partner’s back. Then,

while Voight watched, the white octopus reached under the larger male and

inserted the tip of its arm into the body cavity. The white octopus’s body

began to expand and contract rapidly, a behaviour also believed to signify

mating.


Although in captivity octopuses occasionally indulge in same-sex

encounters, this has never been seen in the wild. Sexual encounters between

distinct species have never been observed.

Could the octopuses be hermaphrodites? This is unlikely, says Voight. There

are no known hermaphrodites among the cephalopods, the class of molluscs that

includes octopuses, squid and cuttlefish. Instead, Voight and Lutz suggest

that maybe the scarcity of octopuses down in the deep ocean makes it of

paramount importance that every time a male octopus encounters another one, it

must thoroughly investigate the possibilities, regardless of species or

gender. If it doesn’t, the male may accidentally pass by a female of the same

species – and perhaps miss a once-in-a-lifetime chance of mating.

The researchers are open to alternative theories. “If anybody can come up

with a good idea,” says Voight, “they should feel free to give me a call”.