Cephalopod Awareness Days: Striking in the Blink of an Eye

While others turn their prose towards ‘pods like the giant octopus or the flashy nautilus, I’d like to take a moment to appreciate the small, unobtrusive, dirt-common, Long-Finned squid (Loligo pealei). They live fast – reaching adulthood, spawning, and dying in less than a year – and can tolerate a wide range of water conditions. They’re the lab rat of cephalopods: their giant axons have been instrumental in working out how nerve cells work. They can also snag a shrimp out of the water column in a fraction of a second. Now you see food, now you don’t. 

The food-nabbing speed comes from a pair of long, thin hunting tentacles held inside the squid’s eight shorter arms. When the hungry squid spies a shrimp, it turns to face it, points its arms toward the prey, then splays its arms open and shoots its tentacles forward with lightning speed. Within 30 milliseconds, the shrimp is stuck on the tentacle’s suckers and is getting pulled toward the squid's waiting mouth.

  

120 milliseconds of a squid catching a shrimp. (From Kier and Van Leeuwen, 1997)

The tentacles are fast because they’re long and thin. In your arm, bones act as levers and muscles pull them to and fro. Squid are boneless, relying instead on muscles arranged in patterns that oppose one another. When muscles running around the outer edge of each tentacle contract, the entire tentacle gets longer and narrower – and since the squid is already sitting at one end, the shape change shoots the shrimp-catching ends of the tentacle forward. 

 

Reference: Kier, W. M. and J. L. Van Leeuwen 1997. A kinematic analysis of tentacle extension in the squid Loligo pealei. J. exp. Biol. 200: 41-53.

 

 

Comments

[John Sullivan]

Very cool. A squid's would seem to require stereoscopic vision to estimate distance to a prey item and yet the eyes on the squid I remember dissecting were 180° opposed. Any idea if and how they achieve that?

[DianeAKelly]

I had to dive into the library to find an answer to that one: turns out that having a body made up mainly of muscle means that squid can temporarily get binocular vision if they need it by squeezing their eyes toward the front of their head. Nice photos of the process can be found at Cepahalove (http://cephalove.southernfriedscience.com/?p=45).