I just stumbled upon a video I took of trematodes from Carpinteria Salt Marsh Reserve, a salt marsh in Santa Barbara County in California. These trematodes have multi-host life cycles and their first intermediate host is the California hornsnail (Cerithidea californica). Trematode eggs get into their snails hosts either by being consumed by the snail or by snail-hunting miracidia which hatched from the trematode egg. Once inside the snail, the trematodes castrate their host (how’s that for rude house guests?) and use the energy that the snail would have put towards reproduction on producing more trematodes. Eventually, the trematode is ready to leave the snail as a cercariae and swim off in search of its second host.

I spent a lot of my summer “shedding cercariae”, which means I was recreating the conditions under which parasites decide to leave their snail host. Placing snails under a warm lamp was all it took and the parasites could be seen swimming around in search of their next host. In the video below you’ll see a California horn snail with little white cercariae swimming around it frantically:

If you’re interested in learning more about these trematodes, check out this blog post on how trematode colonies consist of “queens” and “soldiers”. The researchers who did the study are Ryan Hechinger, Armand Kuris, and Alan Wood. Look for upcoming posts on other research done by Ryan and Armand!

One Response to “Swimming cercariae”

  1. Calimecita

    I hate parasites, while at the same time I have to admire their incredible specializations. Also, many years ago, I hated having to learn all those complex cycles, especially in the case of trematodes with 2 or more intermediate hosts.
    But this is fascinating! It’s been quite a few years since I took my last Invertebrates course and I don’t remember learning anything like this, so thanks for this blog entry!

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