Friday, October 17, 2014

Searching for Ciona (see-o-na)

Ciona intestinalis; note the two "siphons" that the animal uses for filter feeding.
Ciona intestinalis is probably never going to be the star of its own Nat Geo special.  Charismatic it is not; nor is it megafauna.  But this small tunicate (or sea squirt) is a major player in the Gulf of Maine, and believe it or not is our kissing cousin.

Both my marine bio and my friend Beth Richard's developmental bio labs are interested in Ciona.  Tunicates (which include the sea squirts as well as colonial tunicates) are urochordates -- somewhat similar to the chordates (the group we belong to, along with birds, reptiles, fish, and other mammals).  Chordates have several features in common because we all evolved from a common ancestor.  Some of the characteristics we have in common are a notochord during development (a rod-like structure akin to our backbone); a nerve chord; pharygeal slits (in tunicates, these are used for filter feeding; in humans, these have evolved to become part of our faces and other parts of our anatomy); and a post-anal tail (we've lost ours, but still have a "tailbone").

The similarity of tunicates -- which really look pretty blobby compared to us -- is most apparent in its larval form. Beth searches out tunicates so her students can observe the eggs, sperm, and if they're lucky, fertilized eggs and the larval "tadpole" form.  I've only seen this form once, by chance, and let out a whoop that probably confirmed my students' suspicion that I'm a bit nuts.  So I was more than happy to go out collecting with Beth, in exchange for getting to spend some time checking out the eggs, sperm, and maybe larvae.

How do you collect Ciona?  Well, they grow all over docks, so we headed out looking for a likely spot.  First it was off to Dolphin Marina, where we had a lot of luck finding colonial tunicates -- mostly invasive species that smother whatever their larvae land on.  It's hard not to feel bad for that kelp!

Then we hit a lobsterman's dock, where we had terrific luck.  Beth scooped up a "hunk of junk" as I like to call it, and we'd hit the jackpot.  Take a look at all the amazing organisms attached to the side of docks next time you head to the shore -- you might find some Ciona, and you can impress your friends by telling them the blobs are just your kissin' cousin!

Beth, sneaking up on tunicates.
Searching, or napping?  You be the judge.
A "hunk of junk".
Colonial tunicates of several species.  Poor kelp.
More of the blob.
Ciona intestinalis.
The side of the dock at Dolphin Marina.  Interesting hydroids, mussels, anemones, and tunicates.
A wonderland!

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