Seahorses are bony fish but they lack the corresponding scales. Instead, their skin is stretched over bony plates, giving the appearance of an exo-skeleton. A prehensile tail allows seahorses to cling to vegetation preventing them from being washed away in the current.
Feeding predominantly on small crustaceans, an adult seahorse can eat 50 times a day. Seahorse fry can eat up to 3000 pieces of food per day to fuel their growth, ultimately growing to between 1.5 cm and 35.5 cm in length.
Seahorses form the genus Hippocampus, which includes 54 individual species, and are so named for their horse-like head. Hippocampus derives from the Ancient Greek hippos and kampos which means "horse" and "sea monster" respectively.
Distribution and Habitat
Seahorses can be found throughout the world, tending to frequent shallow waters in tropical or temperate seas. Here they can find the seagrass beds, estuaries or reefs where they can find easy shelter from currents and also the prey they feed on.
Perhaps surprisingly, there are two species of seahorse that can be found around the British coastline; the spiny seahorse and the short-snouted seahorse. The latter of which has been found in the Thames estuary.
Contrary to the majority of other animal species, the male seahorse invests the most effort in rearing young, taking care of the fertilised eggs in a brood pouch located on his front after a courtship period that can last several days. During the courtship dance the female deposits her eggs into the male seahorses brood pouch while he fertilises them with his sperm.
After a gestation period of between one and 5 weeks the male undergoes a a birth process including contractions which can last up to 12 hours.
Newborn seahorse fry are independent from birth, spending the first weeks drifting in the plankton layer. One in a thousand will survive to adulthood, the rest succumbing to predation.
It seems that the reason for the swopping of reproductive roles is that the energetically costly process of making eggs in females is offset by the males then taking on the role of gestation. This means that seahorses can produce significantly more young with more breeding cycles in their relatively short lives.
Due to insufficiencies in data it isn't fully known whether seahorse species face extinction. However they do face a number of threats, all of which come down to the action of humans.
It is estimated that the trade in traditional Chinese medicine takes up to 150 million wild seahorses a year while the trade in curios and souvenirs takes around one million seahorses which are left to dry in the sun. In addition, the number of seahorses taken from the wild as part of the pet trade is also estimated at around one million, but perhaps only 1,000 will survive the first six weeks.
Alongside the extraction of seahorses from the wild, the worldwide reduction of coral reefs and seagrass beds will also ultimately effect the survival of this group of fish as their available habitat rapidly diminishes.
- Seahorses are a group of bony fish.
- Their binomial name translates as "horse sea monster".
- Male seahorses become "pregnant".
- During courtship male and female seahorses dance for up to 8 hours.