# Aquatic invert (mussel?) ID needed



## KevinS (Sep 23, 2008)

I found something that seems very odd today while I was out herping. I came upon a few puddles formed in the mud of some large tire tracks and saw what appeared to be small clam shells in them. Every so often, one would turn on its edge and move around very quickly across the bottom of the pool, though none of them ever buried themselves. I thought they must not be clams since I'd never see any mussels move that way and pulled one out of the water. Sure enough, it was a bivalved shell. However, it cracked and what came out definitely didn't seem like a mussel to me. 

From one end, a tail protruded and started making a flipping motion (think of a springtail) and from the other end, two "legs" came out and started moving in the same way. I guess this was how they were scurrying across the bottom. I have no idea what these things are though. The best way I know to describe them is a shrimp in a clam shell based on what I've seen so far. I'm even more perplexed as to how they got in these temporary puddles. I'll try to get some pictures on here soon, but I thought I'd go ahead and see if anyone knows what these might be based on the description first.


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## chuckpowell (May 12, 2004)

Depending on how small they are they could be ostracodes. Ostracodes are bivalved crustaceans that live in fresh or marine water and everything in between. They are very small and I don't know of any larger than 0.125". 

Best,

Chuck


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## KevinS (Sep 23, 2008)

These are a little larger than that (I'd estimate 1/4 inch or so for the length of the shell) but I think you nailed it. I've read in a few publications that salamander larvae eat ostracods, but never really bothered to learn what they were. Thanks.


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## chuckpowell (May 12, 2004)

That's a bit large for an ostracod, maybe a clam shrimp - Branchipodia I believe. I've always want to see one, but never had the chance. It also could be something living in a small, old, mollusk shell. 

Best,

Chuck


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## KevinS (Sep 23, 2008)

I don't think it's anything living in old shells since I saw a dozen or so and never found any actual clams or vacant shells. I may have overestimated the size, but I'll try to get pictures with size reference (I snagged 3 of them to try and get an ID if I needed more pictures). Things are a little hectic since I'm starting a new job, but hopefully I can have some pics up by tomorrow evening. I also tried shooting some video of them swimming around when I found them.


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## KevinS (Sep 23, 2008)

After checking out clam shrimp, I think that's the new winner (and here I was already certain they were ostracods). The habitat these were found in makes much more sense for clam shrimp as well. They're really hard to get decent pictures of, but here are my best efforts so far.


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## chuckpowell (May 12, 2004)

Kevin,

Sorry for the delay in posting but I'm out of town. Those are ostracodes. Large ones, but ostracodes.

Best,

Chuck


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## KevinS (Sep 23, 2008)

Thanks for the ID. Just curious, what is it that points you to ostracods rather than clam shrimp?


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## chuckpowell (May 12, 2004)

Shape and size. Their thick, small and dark. Clam shrimp are usually bigger, thinner, and clear. Also 30 years experience and an invertebrate paleontologists. 

Best,

Chuck


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