Eric couldn't resist these questions and decided to try feeding the larva in the lab. He thought small crustaceans would be a possible prey item, so offered them brine shrimp (Artemia sp.) and filmed the results.
Sometimes I'm not sure whether to tell you what to look for, or to let you watch and discover what happened for yourself. Tonight I've decided on the latter, but I'll also provide some interpretation after the video.
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Pretty scary, if you're a crustacean!
You can see how the larva's outstretched tentacles create a broad surface area for potential prey capture...and that the larva bends its aboral end (the end opposite the mouth) to aid in prey capture, too!
At about 23 seconds there's contact with prey, but it isn't sustained and the brine shrimp is lost.
But at 40 seconds there's success. And at about 1:06 there's a very impressive capture — with a direct sweep from a tentacle to the oral lobes. The oral lobes open so wide they look like small jaws!
At 1:20 you can see two brine shrimp deep inside the gut of the larva after they've been swallowed.
Eric's sharp eyes also noticed that the larva seemed to be generating a directional flow of water towards the mouth (probably via the movement of cilia on its tentacles) — watch for the small particles moving in that direction at about 1:20 through 1:28. He wondered if this current might aid in moving prey that have been stunned by the nematocysts towards the mouth.
So there you have it — feeding behavior of a tube anemone larva. Looks could be a little deceiving — although this larva spends a lot of time drifting quietly with relatively little motion, once prey is encountered, its actions are fluid, swift, and very effective. Beware! ;)