With the head of a horse, the tail of a monkey, the body of an armadillo, and the eyes of a chameleon, seahorses are one of the most bizarre fish you are likely to come across. Early zoologists initially classified seahorses as insects, and not fish, giving them all the generic name Hippocampus (derived from the Greek ' hippos ' meaning horse and ' campus ' meaning sea-monster). They are grouped into the family Syngnathidae which includes pipefish and sea dragons.
Seahorses have few predators due to their bony bodies, over which their scale-less skin is stretched. Being slow swimmers they rely on camouflage to avoid predators and have the ability to change colour to blend in with their surroundings. Many also have the ability to grow long skin filaments to which seaweed and algae can attach giving the seahorse even better camouflage.
Beating as fast as humming bird's wing, the small dorsal fin which is located half way down the seahorses back is its only method of movement. This makes them slow swimmers. They swim in an upright posture using their pectoral fins, found behind their head, for stabilising and steering. Male seahorses stay within small home ranges of 1m² with females moving within 100m², around their male partners.
Seahorses range in size from 16mm Pygmy seahorse (Hippocampus denise) up to the largest seahorse (Hippocampus abdominalis) which can reach 35cm in length. They are distributed globally in both tropical and temperate marine waters, but are found nowhere in vast numbers. They live among seagrasses, mangroves and corals, and most species occur in the West Atlantic or the Indo-Pacific region.
Believe it or not there are two species of seahorse found around the coastline of the British Isles: the Short Snout seahorse (Hippocampus hippocampus) and the Spiny seahorse (Hippocampus guttulatus). The Spiny seahorse can be found living all the way up the west coast to North Wales whereas the smaller Short Snout seahorse is found on the east coast. Both species tend only to be seen in our waters during the warmer months, migrating south to the Mediterranean during the winter. Sightings are rare due to the seahorse's slow movement and fantastic camouflage amongst eelgrass beds so divers often miss them. Any sightings in British waters should be reported to the Seahorse Trust (www.theseahorsetrust.co.uk), who are collating information regarding the distribution of native seahorses.
Seahorses' eyes are able to move independently looking out for food and predators at the same time. They are ambush predators, lying in wait for small fish and shrimps to come within range. They suck food in through their trumpet-like snouts and swallow it whole as they have no teeth.
Paternal care of th
e young is common in fish; sticklebacks provide a well known example - but where as most male fishes only guard and fan the eggs whilst they develop. Pipefish have taken this a stage further where the eggs are 'glued' onto the bodies of the male. Seahorses exhibit paternal care in its most extreme form. They possess a special enclosed brood pouch into which the female deposits her eggs and the male then fertilises them. Incubation can take between 10 days and 6 weeks depending on species and they can give birth to between 50 and 1500 babies each pregnancy. Male seahorses are often pregnant for as many as 7 months in the year.