"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

October 28, 2010

October 28 - Hysteromorpha triloba

Hysteromorpha triloba , a strigeid trematode is a strange looking and generally small parasite found in the digestive tracts of fish-eating vertebrates. The first intermediate host is a snail (e.g., Gyraulus hirsutus), and the second intermediate hosts are fishes of the families Cyprinidae (Abramis sp., Hyborhynchus notatus, Idus idus, Leuciscus sp., and Tinca tinca), Poeciliidae (Poecilia vivipara), and Siluridae (Ameiurus sp.). In the fish intermediate hosts, metacercaria encyst in the musculature (forming white cysts) and the parasite is passed on to the definite host when infected fish are eaten. Definitive hosts include herons, egrets, pelicans, and cormorants.

Other images can be found here.

Contributed by Jessica Light.


  1. I have always said that staining helminths is more of an art than a science and this is a beautiful stain!

  2. this is really beautiful!!
    its like a painting!

  3. And what a name! Hysteromorpha in Ancient Greek means "uterus-shaped".

  4. Thanks Everyone! Everyone should google Harvey Blankenspoor at Hope College and Curt Blankenspoor at Calvin College. They team-teach the Parasitology course at the University of Michigan Biological Station. The course is WONDERFUL. The students get to build our own parasite collections and it's a great experience.

  5. There was a time when every parasitology student learned how to go through a host for parasites, correctly preserve the parasites, and stain and mount them for identification. That time, alas, is no more. Glad it still survives in Michigan.