"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

August 12, 2010

August 12 - Tetrameres sp.

Nematodes often exhibit sexual dimorphism, usually with the males being smaller than the females. An extreme example is found in species of the genus Tetrameres, which live in the glands of the proventriculus of birds. The males look like typical nematodes, long and thin, but the females expand as they become distended with eggs to these bright red, pea-sized individuals that barely resemble nematodes at all, dwarfing the males. As they expand, they can cause pressure necrosis in the tissues of the host.

Post and image contributed by Mike Kinsella.


  1. Can someone please tell me wich especies of tetrameres is showed in this picture?

  2. Tetrameres americana in gallinaceus or Tetrameres crami in Anatidea birds.

    Martín Renato Hernández Castaños

  3. Good picture. I'm studying Vet Parasitology... I'll remember this like the "balloon worm"... Just to make it easier :) Thanks for the information.