Famously, seahorses are the only animals where it’s the males who give birth. Before they have sex, they do a little dance where they form a heart-shape before the female inserts her eggs into the male’s brood pouch. He then ejects sperm into the water before sucking it back into his pouch. To give birth, he hangs onto some seaweed with his tail. He then rocks back and forth and the babies pop out in fives, they ping to the surface to take a gulp of air to fill their swim bladders.
It’s believed that this extraordinary way of doing things evolved from the seahorse's ancient relative – also the ancestor of the modern stickleback - whose males keep guard over their fertilised eggs.
Seahorses evolved about 16.5 million years ago. A seahorse's eyes can move independently of each other and they are the only fish with a neck. It can also use its tail to grasp onto objects, to scratch its head, or even wrap it around its neck like a scarf.
They change colour to mimic their surroundings for camouflage and, as a result, it is hard to know how many species there are; several completely differently coloured seahorses may from the same species. As a result of a survey done by Phd student Sara Lourie in 2004, the total number of seahorse species was reduced from around 100 to only 39.
Six species of seahorse are listed as endangered by the World Conservation Union. This is mostly due to overfishing, either for Chinese medicine or through indiscriminate trawling – they often live in the same areas as the profitable shrimp. At least 25 million seahorses are taken from the sea each year.
Seahorses are among the fastest feeders in the animal kingdom, hi-speed cameras have shown them gobbling up the food in under 6 milliseconds.
They also make chirping sounds by rubbing a bony ridge at the back of their heads against the skull's coronet.
Belief that seahorses have magical curative properties is very old. Diascorides (c. 40-90AD) claimed that a mixture of burnt seahorse and goose fat rubbed on a bald pate would encourage hair to grow.
Pliny the Elder (23-79AD) said that they were an aphrodisiac and, when burnt, that they helped cure a sore side.
These days, dead seahorses are still popular in traditional Chinese medicine. As a powder in tea they supposedly help broken bones, asthma or a weak bladder.
In Japan they are considered an aphrodisiac. Pregnant women across Asia wear a dead seahorse around their necks, turning it into a tea when they're about to give birth in the hope that it will keep them and their baby safe.
Seahorses are monogamous.
The hippocampus was first identified by anatomist Giulio Cesare Aranzi in 1564 and was so called because it resembles a seahorse.
The mascot of the National Society of Epilepsy is a seahorse.
Seahorses can consume 3,000 or more brine shrimp per day.
Because of their body shape, seahorses are rather inept swimmers and can easily die of exhaustion when caught in stormy seas.