October 12 - Acanthocheilus rotundatus

My what big teeth you have! That might be scarier if they weren't on a stomach nematode, but rather the creature that it lives inside. Acanthocheilus rotundatus parasitizes several species of hound sharks (e.g. Galeorhinus galeus, Mustelus griseus). This species was described way back in 1819 and has been found from the Adriatic Sea to the Pacific.

The image is adapted from this paper.