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Competition is stiff in the ocean, particularly for males seeking to spread their seed. That’s why animals have evolved all sorts of different mating strategies, including that of the so-called sneaker male, which is often smaller than territorial males and may have the coloration of a female. In this system—commonly seen among fish—a territorial male guards a nest so its mate can lay eggs, but when he’s not paying attention, a sneaker male will dash in and fertilize the spawn.

Scientists generally assumed that each type of male, the smaller sneaker and the larger territorial one, ejaculates the same way: by quivering and squeezing milt through a small fleshy tube onto a female’s eggs. But because they have different mating strategies, a researcher from Japan wondered if each had a different way of spurting his sperm. For white-banded triplefin, a species of small marine fish in the triplefin blenny family, at least, the answer seems to be yes.

Kazutaka Ota, a marine biologist at Osaka Metropolitan University in Japan, observed wild white-banded triplefin off the coast of Japan and found that the two male morphs have unique semen-shooting shimmies.