"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

January 20, 2010

January 20 - Neoechinorhynchus emyditoides

Neoechinorhynchus emyditoides is a species of acanthocephalan, or thorny-headed worm. These parasites often have very complex life cycles involving multiple trophic levels. The vertebrate host of this species is a turtle and, as the picture shows, a single turtle can have hundreds of worms – in some cases, more than 1000! - filling its intestine. The acanthocephalan eggs are expelled in the turtle’s feces and are eaten by ostracods, tiny crustaceans, where they develop into a stage called an acanthella. When fish eat the ostracods, the acanthella travel to the fish’s liver and await the fish’s ingestion by a turtle. There are 10 species in this genus and they are extremely difficult to tell apart. This photo likely contains a mix of both N. emyditoides and Neoechinorhynchus pseudemydis. The host in this case was a red-eared slider (Trachemys scripta) collected from Reelfoot Lake, Tennessee.

Nomination and photo by Mike Barger.


  1. So how DO you know if there are different species to begin with?

  2. A very good question. I think it's best to quote Mike Barger, who studies these creatures and sent in the information to me, because he just says this so well. According to Mike, "the males cannot currently be identified to species, and the females can only be identified based on the contour of the posterior end (they variously have digitiform processes, clefts, bumps, etc.) and their mature eggs (some of which are, to me anyway, shockingly beautiful)."

    Sounds like a perfect place for some DNA bar-coding to me!

  3. I would very much like to see these shockingly beautiful eggs! Would Mike Barger share some photographs?

  4. Thanks Susan!

    It would be interesting to barcode them, and in this case it calls for some more serious phylogenetic analysis (rather than just blast everything you have), which is all the more exciting.