Flounder are SOL with mystery eye parasite

Parasites have been found sticking out of more flounder eyeballs than usual. Credit: A. Morton

You think you’ve got problems. Arrowtooth flounder, a flatfish found along the West Coast, have been turning up with more parasites lately.

And not just any parasites. The copepod Phrixocephalus cincinnatus burrows into the eyeball of the flounder and anchors itself inside,tapping into the bloodstream to feed its string of eggs now streaming from the fish’s eye. Fish, of course, have a tough time seeing with them. When the eggs hatch, the eye loses sight completely. Flounder with copepods in both eyes are pretty much screwed.

Shrimp trawlers fishing in British Columbia for years have recently noticed more of the creepy critters on flounder near salmon farms, and Dane Stabel, a parasitology graduate student at the University of Victoria, wants to find out why.

Little is known about the copepod’s biology—no one has ever seen an adult male or any juveniles, and no one knows why the parasite chooses the sanddab over the arrowtooth in California, even though both fish live in both places. With so much still to discover, Stabel offers loads of possibilities for the recent spike: more fish gathering near farms makes it easier for the parasite to spread, for example, and the extra nutrients and waste in the water could compromise the fishes’ immune systems. Half the picture is still missing: the identity of the animal that hosts the copepod for the rest of its lifecycle is a mystery. Stabel suggests it could be a polychaete worm that thrives in sites too polluted for other animals.

Over the summer, Stabel hopes to quantify how many flounder are afflicted to see whether the shrimpers’ reports hold water. Ultimately, he plans to uncover details of the copepod’s ecology—if he can keep quelling his gag reflex.