Tuesday, November 27, 2007

Follow-up on kelp crawlers

A local naturalist, in the comments to my previous post, suggested that the creatures we photographed may have been tunicates, possibly Ciona. Thanks, Hugh.

I have spent most of the evening looking at photos of tunicates of this area, and reading what I could find on their locations. Hugh could be right; Ciona looks possible.

There are five invasive species of tunicate in the area, Ciona savigny, Styela clava, Didemnum sp., Botrylloides violaceus, and Botryllus schlosseri; of these, only Ciona looks like it may match. The colour is right, the shape is almost right, and some of the groupings show circles that may be siphon mouths.

Two similar native species, Corella inflata and Corella willmeriana, are smaller and rounder. They don't match mine. Besides, Corella inflata dies within a few days if exposed to sunlight.

Many tunicates eat anenomes, but Ciona savigny is a filter feeder, eating bits of waste. There are obviously no anenomes on this kelp.

Most of the tunicates live at greater depths, out of the sunlight, but a few are found under docks and floats. Most of them, including Ciona, fasten to firmer ground, though; pilings, rocks, even mussels. These were on kelp.

A couple of the things look definitely like Melibe leonina, which is transparent and usually found on eelgrass. I found one mention of it on kelp.

Several of the other shapes could be Melibe, as well, either singly or in groups. Do Melibe hang out together in flocks? Or could this be a mixed bag, Melibe and Ciona? Do they mix?

And should I report these as invasive species? And to whom? The address I have is for across the border.

Every question leads to a list of questions, doesn't it?


  1. Hi Weeta,

    Could be Ciona, If it is invasive and not previously reported for your local, you might want to report it to the local fish and wildlife (or comparable) agency.

    I'm not sure where you heard that tunicates eat anemones?? That is certainly not the case. Tunicates are filter feeders by design. Maybe you are confusing them with nudibranchs?

    It also looks like you you might have an anemone or zoanthid on the kelp fronds as well the tunicates (the blobby things). Its hard to tell from your pictures, but I definitely see tentacles and radial symmetry.

  2. Lower right corner of photo.

  3. Thanks, Kevin.
    I may have misunderstood the bit about tunicates eating anemones, or someone else did. I couldn't find the site where I (mis)read it, earlier.

    It is too bad that the kelp was several meters below us, off the pier, and not reachable. I should have gone back to land for a long branch or something, and pulled it up to look at it. Next time.

    I see what you mean about tentacles.

    And I will report this. Thanks again.

  4. Those are indeed Melibe leonina. They're often found in aggregations on kelp as well as other algae and sea grass.

  5. Thanks, Leslie!

    And welcome to the blog! (And to Blogger, too. Do you plan to set up your own blog?)

  6. No, it's much more fun to see what everybody else has to say then swoop in on the interesting stuff!
    Cheers, Leslie


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