Seahorses are pipefish remade into upright horse-headed swimmers
A seahorse is any of forty-seven Hippocampus species—small marine bony fishes with horse-like heads, segmented bony armour, grasping tails, and independent eye movement. The genus name comes from Greek hippokampos, fusing the words for horse and sea monster.
Anatomy and genetics show they are highly modified pipefish; fossils are scarce. Molecular clocks place the split in the Late Oligocene, perhaps as new shallow seagrass meadows rewarded upright sit-and-wait hunters.
Sizes run from 1.5 to 35 centimetres. Instead of scales they have thin skin stretched over rings of bony plates, the ring count differing by species, and each species also wears its own crown-like coronet. Unusually for a fish, the neck is flexible and well defined. They are dismal swimmers, fluttering a dorsal fin and steering with the pectorals; the dwarf seahorse, H. zosterae, manages only about 1.5 metres an hour, the slowest fish known, so most time is spent with the tail wrapped around something fixed.
That upright stance may be the point: it lets a seahorse snap up small shrimp from farther away than a pipefish can. With no stomach and a very simple gut, they must eat almost constantly, ambushing crustaceans from cover. They live in shallow tropical and temperate seas between about 45 degrees south and 45 north, in seagrass, estuaries, reefs and mangroves, with colonies even in the Thames Estuary. In the Mediterranean, males keep to about a square metre while females roam roughly a hundred times that.
Breeding reverses the usual roles. After days of courtship, including a synchronized predawn dance, the female places up to 1,500 eggs in a pouch on the male's tail, and he carries them for 9 to 45 days before releasing tiny, fully formed young, often mating again within hours or days.
Source: Seahorse
