Science Buddies: "Ask an Expert"

I have recently been working on a project were you expose Daphnia to a questionably toxic sediments and observe their reaction to them. Before I began this experiment, I began observing tiny organisms in the Daphnia tank that shared no similarity towards them whatsoever, But I concluded that a they appeared from the Daphnia food for this colony only appeared after I put in the Daphnia feed, however their populations have been dramatically increasing and it was made clear that they are most certainly not food. For one thing they are very small and fast, much faster than the Daphnia magna that I purchased, and they don’t share a likeness.I have also observed that another peculiar looking colony has risen but these ones share a remote likeness to the Daphnia magna that I purchased but they are faster, smaller, have larger antennas and apical spine. Can you please tell me what these creatures are for I need to know for my science report.
Can you also please let me know the possible reason for their appearance for they were spotted before anything was done to the daphnia.

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Hi, nerdoc! To be clear, I know very little about Daphnia, so I'm making a totally uneducated guess: is it possible that the Daphnia have reproduced, and what you're seeing is the larvae/offspring? (Try looking up Daphina reproduction and offspring to see what that shows you.) Good luck!

Thank you for your feedback, I asked a scientists at Carolina Biological what the species were and they reported that they were a form of unknown copepods which were accidentally sent with the Daphnia. Copepods are a form of freshwater crustatien just like the Daphnia, but they share multiple differences as they have different strands on DNA and genetic makeup, but thank you for your reply.