"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

May 22, 2010

May 22 - Placobdella parasitica

Today's parasite, the leech Placobdella parasitica is an excellent parent. Not only can it perform both motherly and fatherly duties simultaneously (it's a hermaphrodite), it also takes good care of its young. These leeches spend most of their lives on turtles, particularly snapping turtles, where they will feed on the blood primarily around the leg pits and tail (where the turtle's formidable jaws can't reach them.) They brood their young on their ventral surface protecting them there until they are big enough to feed on their own, which sometimes means transporting them to their first meal. Despite the caring nature of the leeches post reproduction, the conception of those young is actually quite violent. Leeches will stab small spermatophores into each other in a process known as traumatic insemination. Yipes.

Photo by Mark Siddall.


  1. Very cool. How large are the leeches? By the way, thanks for the blog, I really enjoy reading about the funky parasites out there.

  2. These guys are about 1-3 inches long.

    Glad you like the blog!

  3. I have a picture of a completely engorged placobdella...how can I get it to you?

  4. Sondra - you can email it to me at perkins@amnh.org.

  5. I found one of these in the pond by my house. I took a video with my phone. I live in Tallahassee, FL.

  6. I found one of these in the pond by my house. I live in Tallahassee, FL. I took a video of it with my phone.