Identification Requests

During my plankton grab in St. Simon this year, I had so many different kinds of plankton to observe. Some, like the crab larvae, I could identify by sight. Some I needed to do a bit of research on. The exact species of this bristle worm, for example, is something of a mystery to me, but I’m reasonably sure of what it is (interestingly from a behavioral standpoint, this worm swam right up to my phone’s flashlight; freshwater plankton tend to be a bit photophobic, I’ve noticed, but tidal plankton tended to be attracted to lights, making them much easier to catch).

Other creatures still sort of evade identification, either because I lack the vocabulary to describe them thickly enough, or because I’m not sure where to start looking for what they are (are they plankton or some kind of monocellular organism?). So I turn to you all today to request some information. The first thing is what I’ve almost certainly incorrectly identified as a trocophore.


It was marine life, actively mobile and visible to the naked eye as a whitish speck. It looked like a highly mobile mote of dust. Magnified, it appeared to have to eye spots and a large dent in the middle of it. It’s cilliated.

Trocophore Larva 4

My closeups are, unfortunately, a bit blurry, but you can see that it seems, anyway, to be multicelled. Unless the granules you see in it are its cytoplasm.

The other thing I caught was some kind of crustacean. I identified it as some kind of hermit crab, but I’m not 100 percent convinced of that.

It made its home in what seemed to be the broken off tube of a marsh reed. As with the other, it was visible to the naked eye, but not easily spotted. What makes me think it’s not a hermit crab is I observed it swimming by flitting in and out of the tube.

Hermit Crab

So I turn it over to you all. Any thoughts on what these might be?

3 Comments Add yours

  1. Manu Prakash says:

    @Matt: great work. Could you please share with everyone how you do your plankton collections .. Also a picture of the location would also add context to the site.

    Now, on for identification – let’s first start with the larvae. It’s absolutely a multi-cellular larvae. I can see the cilia surrounding the larvae (they swim quiet actively in slow water); also – it appears to be a grastula – with a fold.

    Also; I noticed the blur on your lrns; that comes from things accumulating for long time. Take the lens out; use clean tissue paper and water and wipe the lens – and let it dry well. You will see; the blurr will go away 🙂


  2. Matt.Rossi says:

    @Manu that makes perfect sense; now that I look it up, I see it’s a starfish gastrula. See, it’s always the vocabulary that makes it difficult to search.

    You’re right, also, about the build up on the lens. Saltwater is particularly bad if it gets on the lens because it leaves behind a mineral deposit.

    I’ll post in a little bit about the tool I use to catch plankton. A plankton net’s pretty easy to make, actually.

  3. Manu Prakash says:

    @Matt: I would love to see the plankton net you use/build. Imagine all the people living next to the ocean..


Leave a Reply