Unidentified marine organism

[psyke]

Hey! A while back I've posted a thread asking for help with a Celestron microscope/DSLR camera setup. Since I didn't want to mess up my Cannon sensor just yet in an afocal setup, I've used a cheap usb webcam for this video.

http://www.youtube.com/watch?v=YZuRXtVA13E

This sample was taken from the Black Sea in Romania, Constanta. Even if I remember reading a few other threads about similar organisms, I'm really having a hard time identifying the species. I'll guess it to be a Rotifier but I could be *way* off.

The second question is about that mysterious dark spot. It is not on the eyepiece since there is no eyepiece used. It is not on the objective since it is present at each level of magnification. I can't really see it when I'm looking through the eyepiece though.
L.E.: It is not on the sensor either.
L.L.E.:It actually was on the sensor. My bad.
Any ideas on where else it might be and how could I remove it?

Thank you in advance.

[Bob Ballantyne]

Definately not a rotifer, which is in a small group of organisms known as Rotifera and have no exoskeleton. More "wormlike."

It is an arthropod for sure, most likely a crustacean of some sort. Looks something like the larval form of a cyclops.

Bob B

[Charles Krebs]

That is a nauplius. It is a larval stage of a crustacean. The nauplius of many creatures look quite similar, and I can't help ID it beyond that point.