"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 23, 2010
May 23 - Proteocephalus pinguis
Proteocephalus pinguis parasitizes pike (how about them P's??). These are tapeworms (cestodes) that alternate between their fish hosts and copepod intermediate hosts. They have extremely simple scoleces and are small even as adults. The genus contains many other species that have similar life cycles, alternating between vertebrates and copepods. If the first vertebrate host gets gobbled up by a bigger one, then the tapeworms simply infect this host instead.
The photo is from this website.