A species
Lined seahorse
Hippocampus erectus
The upright fish where dads give birth.
You and the lined seahorse last shared an ancestor about 430 million years ago (on 24 November, if life's history were one year).
Imagine a fish that stands up like a tiny horse. The lined seahorse swims upright, with a horse-like head, a curled tail for gripping and a little crown on its head. Surprisingly, it is a true fish and a close relative of pipefishes and seadragons. Strangest of all, the males get pregnant.
The female passes her eggs into a pouch on the male's belly. He carries them until they hatch, then pushes the tiny young out into the water. Lined seahorses are poor swimmers, so they often hide rather than flee. They come in colours such as yellow, orange, brown, green, grey or black, and each one can quickly change shade to blend with seagrass, coral or mangroves.
Instead of scales, they wear armour made of about 50 bony plates. Often gripping with the tail, they wait in mostly shallow, salty water in the western Atlantic. When tiny shrimp and other small animals drift past, they suck them up.
Eyes that look two ways
Each eye can swivel on its own. The two eyes can also line up to look at the same thing together.
A buzzing back fin
Like other seahorses, it moves with fast beats of the single fan-like fin on its back, up to about 70 beats each second. Two tiny fins by the head help with balance and steering.
A short life
Lined seahorses live only about one to four years.