Deep sea lanternfish help transmit parasites to sperm whales and giant squid, new research shows.

These parasitic worms, known as Anisakis brevispiculata, infect dwarf and pygmy sperm whales, strange and poorly-understood creatures found worldwide. The study, published recently in Deep-Sea Research Part I, sheds light on these mysterious creatures—as well as the parasites, closely related species of which can infect humans and cause severe symptoms.

“Anisakis are pervasive everywhere in the ocean,” and yet very little is known about them, says Francisco Aznar, associate professor in zoology, in the Marine Zoology Unit at the University of Valencia in Spain and one of the study coauthors.

Lanternfish are bioluminescent, producing light in the dark, deep sea habitat where they spend