The Victorians thought the seahorse was an insect – and it’s easy to see why. With its hard, bony armour and unusual swimming style, it seems to defy all expectations of what a fish should look like.
But while it might seem like an oddity of the ocean, it’s more simple than we think.
So, why is a seahorse technically a fish?
While it might not look like a typical fish, the seahorse is in fact a true fish – with a swim bladder, fins, a hard skull, and no limbs with digits. We included seahorses in our round-up of the most beautiful fish in the sea.
Unlike other fish, however, the seahorse swims upright, finding seagrass habitats that serve as camouflage for its upright posture. It propels itself forward using its dorsal fin, while the small pectoral fins near its head offer steering and stability.
There are also a number of other factors that set a seahorse apart from other fish. It also has a curled prehensile tail, which can grip or hold objects. Along with pipefish and pipehorses (two other members of the Syngnathidae family), the seahorse is the only fish with a prehensile tail.
Instead of scales, the seahorse has skin stretched over bony plates which give it a protective armour. These plates are fused together, which means seahorses are not as flexible as scaled fish and are more rigid in structure.
Interested in seahorses? Find out more about how and why seahorses change colour, why seahorses look like horses, and the incredible way male seahorses get pregnant.
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Top image: Slender seahorse (Hippocampus reidi) or Longsnout seahorse (credit: Getty Images)