Wednesday, 29 July 2015

Jelly and Tadpoles are a Bad Mix

Image: UAF
You can't be too picky about what you eat when you live in the Arctic. If you insist on residing amid such bitter cold and ice, you better be prepared for that layer of blubber that clings to everything you eat. Perhaps that's why most Comb Jellies stick to warm, tropical climes.

Most, but not all!

Image: Elisabeth Calvert
Mertensia ovum
Like those other, sun-loving Comb Jellies, the ones that lurk beneath or near Arctic sea ice are basically gelatinous bags that swim around in search of prey. They swim using 8 rows of tiny cilia that look like regiments of eyelashes that fall like dominoes and then raise up again Mexican wave style. They catch their food using two, long tentacles each armed with numerous sticky cells that ensnare prey.

Usually copepods and shrimp make for good eating but... they can also catch other things. And eat them. Even though they're composed almost entirely of stuff they don't want to eat.

Video: Our Oceans
Dryodora gladiformis (?) eating and not eating

Enter the Larvacean. These tiny creatures look just like tadpoles and are related to sea squirts, who also look just like tadpoles, but only when they're young larvae. Sea squirts grow up into weird jug things attached to the sea floor, Larvaceans on the other hand always look like tadpoles.

Sounds like good eating! But there's a great, big, somewhat snotty problem. Larvaceans feed by building a huge structure out of mucus called a "house". The Larvacean lives inside it, carrying it along as it swims and using it to filter out plankton.

To get at the Larvacean, a hungry Comb Jelly has to eat the entire house along with its resident! And its no gingerbread house, either. It's mucus. And even Comb Jellies think that's a bit nasty. So the Comb Jelly opens wide (VERY wide! Because it's basically a gelatinous bag, remember?) and regurgitates the house whilst keeping hold of the Larvacean.

It makes me wonder what kind of strange, internal gymnastics the Comb Jelly might have done to achieve such a trick. Or did the Larvacean just wriggle out and the Comb Jelly was all "welcome to your new house. Sorry for the lack of amenities but not to worry, you shan't be staying long. Bwaaahahahahaaaa!"

I don't know if Comb Jellies do those kind of sinister quips but it's good to see that if you can't deal with the blubber yourself, indigestion will do it for you.


Big thanks to Will for bringing this most impressive gob to my attention!


TexWisGirl said...

this process sounds gross.

Christopher Hall said...

I think the Larvacean did swim out, since the home had stopped moving. Its struggles just moved it out of its home. The jell can then spit out the indigestible, nasty bit. Now, it'd be intentional if the jelly maneuvers to swallow the Larvacean from its front end, so that it swims forward into the "stomach". It'd be hard to find out, if this is one the first times it's ever been taped.

I just HATE it when I have spit out a huge mucus shell.

Joseph Jameson-Gould said...

@TexWisGirl: It probably is!

@Christopher Hall: Yeah, I'm sure you're right. It would be interesting to know if the comb jelly has to do anything in particular to get Larvacean out of there.

Totally agree on the huge mucus shells. Bane of my life!

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