What parasitic copepod is commonly found attached to Greenland shark eyes?

Ommatokoita elongata is a parasitic copepod commonly found attached to Greenland shark eyes.

This small crustacean is a specialized marine parasite associated particularly with Greenland sharks and other sleeper sharks. It attaches around the eye, where its presence can damage or cloud the host’s vision. Researchers have proposed that the copepod may obtain food from tissues or fluids around the eye, although details of the relationship have been studied from limited observations.

The parasite is often described as bioluminescent, and one hypothesis is that its glow could help attract prey toward the slow-moving shark. That interpretation remains a proposed explanation rather than a simple proven fact about every infection.

Greenland sharks inhabit cold North Atlantic and Arctic waters and are among the longest-lived vertebrates known. The copepod’s scientific name is easy to confuse with names of salmon lice, which are different parasitic crustaceans found on salmon and other fish.