Your commute may be bad, but at least you don’t have to worry about blood-sucking parasites.

This species undertakes daily migrations from coral reefs to food-rich seagrass beds, returning home to the reefs in the morning. (Unlike most fish, which have vertical migrations, grunts move horizontally through the ocean.)

During the grunts' trek—up to a kilometer long—they're highly susceptible to infestation by tiny, parasitic crustaceans called gnathiids. ("Meet 5 'Zombie' Parasites That Mind-Control Their Hosts.")

In part because gnathiids aren’t very active on the reef during the day, Sikkel wondered if the fish's nightly journeys help them avoid the parasite, which can be fatal.

In experiments published in March, Sikkel and colleagues found support for this hypothesis: Grunts forced to stay