This is a picture I took of the brain of a common East Coast killifish, the mummichog (Fundulus heteroclitus). The red arrows point to metacercariae, which are a stage of trematode found in intermediate hosts. I believe that this parasite is Diplostomum nassa. This trematode will only be transmitted to its definitive host (i.e., the host in which the parasite can sexually reproduce) if the mummichog gets eaten by this host. This is called “trophic transmission”.

4 Responses to “Parasites on the brain”

  1. Emerson White

    You’re back, yay! Quick question, is there any kind of differential staining that can make these guys stand out more?

    • weinersmith

      Yeah! I submitted my last grant of the season and am back to blogging!

      Yes, I could remove this parasite and stain it to make the internal features stand out more. Unfortunately, I was 1) at the lab of a collaborator who I don’t believe had the appropriate stains and 2) I don’t know much about parasite staining techniques. I’m hoping to learn more about stains this quarter and will hopefully have more detailed photos to share as I get more experience. Thanks for sticking with me through the dry spell! 🙂

  2. Daniela Duarte

    Wow! Nice picture there.
    What’s it’s host? Just any vertebrate?

    You’ve got a wonderful blog. Congratz.

    • weinersmith


      I don’t think we’ve worked out all of the details yet, but the first intermediate host is some east coast snail, and the definitive host is probably some predatory bird.

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