ID help

[fzs122]

Did you match these images up with anything on the Internet, maybe with Google images?

Yes. That is what led me here.

Thanks for corroborating they may be larval schistosomes (Cercariae). Frankly, I was getting too many conflicting results to determine which route was worth spending more time on before that.

It turns out the shape is identical to what I just found here (thanks to your encouraging information) describing a "free cercaria" of a Trematode.
Wikipedia - Trematode life cycle stages

Since prazi only works on adult flukes, I guess I should wait until fish exhibit fluke symptoms to begin dosing.

Incidentally, I received feedback from elsewhere that it could just be a copepod that has eaten Red Gracilaria. I'm not trying to stir the pot, but I'd sure love to zero in on this some more. I'd be ecstatic if it just ended up being a gut loaded copepod (although I haven't been able to find any further evidence to that end).

 

[Jay Hemdal]

Yes. That is what led me here.

Thanks for corroborating they may be larval schistosomes (Cercariae). Frankly, I was getting too many conflicting results to determine which route was worth spending more time on before that.

It turns out the shape is identical to what I just found here (thanks to your encouraging information) describing a "free cercaria" of a Trematode.
Wikipedia - Trematode life cycle stages

Since prazi only works on adult flukes, I guess I should wait until fish exhibit fluke symptoms to begin dosing.

Incidentally, I received feedback from elsewhere that it could just be a copepod that has eaten Red Gracilaria. I'm not trying to stir the pot, but I'd sure love to zero in on this some more. I'd be ecstatic if it just ended up being a gut loaded copepod (although I haven't been able to find any further evidence to that end).

My first thought in seeing these was also a copepod - due to the twin tails, copepods show those (egg sacs). However, there are no evident body segments, so they are not crustaceans. They are indeed larval trematodes released by some snails.

Side story - I once had a staff diver report that something tried to burrow into her arm while diving in a tropical freshwater tank. She drew a picture for me, it was clearly a larval trematode, but she said it was 1/2” long!