Animal of the Week -- January 14, 2008

Good morrow good women and gentlefolk,

It was a most pleasing moment last week when a colleague forwarded me a link to a news story, not about a pair of twins getting married (http://news.bbc.co.uk/1/hi/uk/7182817.stm), but about a Pacific giant octopus playing with a Mr Potato head (http://news.bbc.co.uk/1/hi/england/cornwall/7179368.stm). The giant mollusc loves his toy, mostly because it's got crab meat inside it (which is a feature I don't recall from the Mr Potato Head that I had), but also its bright colours and moving parts. Now, as you might guess, the Pacific giant octopus (Enteroctopus dofleini) is a big octopus, reports of a 272 kg, 9 m, specimen are highly doubtful, but a 71 kg live specimen is confirmed. But it turns out that this size record is rivalled among the octopodes by a bizarre freak of the molluscan world -- this week's animal of the week is Haliphron atlanticus (the seven-arm octopus). Of which a dead specimen weighed in at 61 kg, giving an estimated live weight of 75 kg, and had a mantle length (the head-like bit) of 40 cm.

What? I hear you cry. How can there be such a thing? Surely this septapode octopus is a contradiction in terms, and cephalopod oxymoron, a lie, a fabrication, a genetic freak or frankenstein fish. No, I tell you, it is real, a proper species.

The truth is that the distaff representatives of the species have the full complement of octopus legs; but once more, in the face of all we expect to be true about the natural world, the males are missing a limb. In octopuses (please, not octopi) and other cephalopods (squids, cuttlefish, and nautili), the males have a specially adapted limb, the hectocotylus, which is used to deliver sperm to the female. In many other octopuses this arm is larger than the others, but in the seven-arm octopus, this sperm arm is small and coiled up in a small pouch underneath the right eye. During the act, the male unfurls his arm from beneath his eye and makes a special delivery to a cavity under the female's gelatinous mantle. So I guess, "giving her the eye", means something much more intimate in octopus courtship than in human relations.

Bye then!

Peter Hayward
Head Keeper
Animal of the Week