Seahorses Are Weird

Though they look more like a stallion or a chess piece, seahorses are actually fish. They exhibit several other oddities than just their horsey looks, though.

While most fish are covered in scales, seahorses have bony plates over which a thin layer of skin is stretched.

They have a vertebral column running through the center of their body to the tip of their tail, which is prehensile and propels them through water.

Finally, and oddest of all, seahorses are the only known animal where the male gets pregnant. As they intertwine their tails to mate, the female extends a tube, called the ovipositor, into the male's "brood pouch" and deposits eggs. The male fertilizes the eggs and carries them for a few days or weeks, depending on the species. When it's time for the baby seahorses to go off on their own, the male pumps his tail until the swim out of the pouch.

This illustration of a seahorse's vertebral column was created by Elina Mer for the Princeton University 2006 Art of Science Competition.

--Bjorn Carey

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Credit: Elina Mer/Princeton U. 2006 Art of Science Competition