“A fish shaped like a chess piece, where the dads get pregnant.”

The seahorse is a fish that decided not to look like one. It swims upright, terribly, propelled by a tiny fluttering fin at a top speed best described as "eventually." It anchors itself by wrapping its prehensile tail around seagrass and can change color to vanish against the background. But its headline feature is reproductive role-reversal: the female deposits her eggs into a pouch on the male's belly, and he carries, nourishes, and eventually gives birth to the babies in a series of dramatic contractions. Hundreds of tiny seahorses spill out, fully independent, while dad recovers and frequently gets pregnant again within days. Many species also mate for life and greet each other every morning with a little dance. It's a fish, technically, but it's clearly running a different operating system.

Scientific name

Hippocampus

Size

From a fingernail to a banana, depending on species.

Habitat

Shallow seagrass, mangroves, and reefs worldwide.

Diet

Tiny crustaceans, slurped through a snout.

Conservation

VU · Vulnerable

Picnic threat level

Picnic threat: none. Too busy being pregnant and elegant.

Hans Hillewaert, CC BY-SA 4.0, via Wikimedia Commons · Learn more →