Little monsters under the microscope: Parasites in our Largemouth Bass

“I have no idea what this thing is, some sort of a spiny-headed worm or something,” called out Michelle, a technician in the lab. Transfixed by the insidious creature, she zoomed in with the microscope to take a closer look as she described what she saw. “It looks something like a small leech, but instead of a sucker it has a hardened front end with recurved spines.” “Recurved spines?” I thought, sounds nasty! The little monster was a quarter of an inch long, but under the microscope it was clear that this animal meant business. It had clearly been shaped by evolution to do one thing very well: embed itself and never let go.

The thorny-headed worm, Acanthocephala, under our microscope. Recurved spines on the head (upper left side) enable it to remain lodged in the gastrointestinal lining of its host.

It was our first day looking through the stomach contents of young Largemouth Bass that we had captured this fall, and I was in the process of training each of the technicians on how to properly dissect the stomachs and identify their contents. I was used to seeing the normal diet items, such as zooplankton, aquatic invertebrates, and small fish, but I had never seen something like this! Continue reading