Squid-fishing for the wily Taningia danae

Since I asked for it, and since so many were promptly forthcoming with a copy, I'd better give you a quick summary. Kubodera et al. have formally published their observations of the eight-armed deep sea squid, Taningia danae, that were in the news last February. There isn't much new information in the papers; it's all based on a handful of video observations of hunting squid in their native habitat, so it's more on the side of anecdote than anything else right now. It's still just plain cool.

That photo is of their video gear. It's a platform with lights and cameras that's lowered on a cable to almost a thousand meters. What I thought was cute, though, was that object jutting off at about 45°—that's a fiberglas fishing pole with a short length of monofilament line dangling the bait in front of the cameras. It's so jaunty to strap a pole to your robot and send it off to go fishing.

And here's what it's all about: catching a squid in action. This is a specimen of Taningia, about 1 meter long, charging the bait, flaring its arms outwards, and snagging it with its ventral most pair of arms as it swings around.

There are two main things learned from the movies. Taningia is a deep-water squid that uses vesicles of ammonia in its tissues to maintain neutral bouyancy—when you see these kinds of squid dead and hauled up on the deck of a boat, they are incredibly soft and flabby, almost jelly-like in consistency, sort of like some college professors. They certainly don't give the impression of being a dynamic sort of animal, and some species found at this depth are thought to be passive fishers, with long dangling feeding tentacles that they use to snare passing meals and haul up to their beak. That is not the case here; Taningia is a fast-moving, aggressive predator.

The other surprise is the way the squid used its photophores. It has light generating organs on its arms, and in the run up to the bait it flared its arms wide and flashed 1-2 second long bright pulses of light at its prey. It's unclear what the purpose of such displays might be. It could be to startle or disorient prey (the bait was dead, so unfortunately we did not see how an animal reacts to the appearance of a brightly blinking squid), or it could be to illuminate a target so the squid can more accurately orient towards it.

Obviously, more study is needed.

Kubodera T, Koyama Y, Mori K (2007) Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae. Proc Biol Sci 274(1613): 1029-34.