THE KNYSNA SEA HORSE- HIPPOCAMPUS CAPENSIS

Like Knysna itself, the sea horse's greatest asset - its unusual beauty - is, sadly, its greatest weakness. The Knysna sea horse, which is one of the strangest fishes of the Knysna Lagoon, is a favourite with visitors and locals alike. An understanding of its uniqueness may help to ensure its continued existence.From our earliest history, men and women have been fascinated by the sea horse. It features in the myths and legends of many cultures, and has been depicted in art, crafts and jewellery.

During this century, however, fascination has lead to the threat of extinction: no longer content with the depiction of the animal, man has found it necessary to collect and keep it in captivity. This has been made possible by the invention (and increased safety and popularity) of scuba diving, as well as by the invention of the marine aquarium. Sea horses are in demand as aphrodisiacs in the east, and have been collected for the curio industry (where they have been dried and encased in resin to serve as key holders, paper weights, etc.).

THE GENUS HIPPOCAMPUS - THE SEA HORSES

Seahorses are found in most of the world's shallower seas - from Tasmania in the south to the English Channel in the north.

All seahorses belong to the genus Hippocampus and all have similar breeding habits. There are between thirty and forty known species, ranging from the largest - the Eastern Pacific Sea Horse (Hippocampus ingens),which measures up to 40 cm - to the smallest - the New Caledonian Sea Horse(Hippocampus hargibanti), which is only 15 mm long.. Although specimens of up to 12cm in length have been recorded, the average Knysna seahorse is about 7cm long. It is the world's only known estuarine seahorse species and is found in the Keurbooms, Swartvlei and Knysna estuaries - and only in areas within these estuaries where dense vegetation is present. It occurs nowhere else in the world and, because of its limited distribution and environmental degradation within its range, is listed as endangered on the lUCN's Red List.

A MALE PREGNANCY!

Seahorses are known as the chameleons of the sea because of their ability to change colour to blend in with their surroundings in much the same way as chameleons do (and, like the chameleon, their eyes can move independently).

The tail is strong and prehensile (adapted to seize and grasp), and a seahorse that has wound its tail around a holdfast of plant material, sponge or rope can be almost impossible to dislodge. Although seahorses appear unusual they are, in fact, true fishes with backbone, gills, swim bladder and fins. Their bodies are enclosed by an insect-like armour of bony plates covered by skin. The dorsal (back) fin is used for propulsion through the water, and the pectoral (side) fins are used to stabilise and steer. The unusual arrangement of their fins makes them slow swimmers, and seahorses rely on camouflage to escape detection by predators.

Enemies of the seahorse include crabs, larger fishes and man, and they're susceptible to fungal, parasitic and bacterial disease. And, because they tend to live at shallow depths, storms can also contribute to their mortality by dislodging their holdfasts and throwing them ashore.

It's thought that most species mate for life and their reproductive habits are quite unusual: pregnancy occurs in the male! He has a brood pouch in his belly, and can easily be distinguished from the female because her belly is much slimmer than his (he looks like he has a 'beer belly').

The Knysna seahorse becomes sexually mature between 6-9 months after birth, depending on the water temperature and the availability of food.Their mating ritual typically takes three days to complete: the couple grips onto a hold fast, dancing around it in graceful display and frequently swimming in tight parallel formation to other hold fasts. On the third morning of the ritual, the female's ovipositor (the organ with which she places her eggs in the male's pouch) begins to protrude from her body. The male indicates that he is ready to mate by arching and jack-knifing his body vigorously, thus compressing his pouch and pumping water in and out of it. When both male and female are finally ready, they let go of their hold fast and swim slowly upwards as she transfers her eggs into his brood pouch to. The entire clutch of eggs is transferred in one action, which typically takes about six seconds.

After the ovipositor is withdrawn and the brood pouch is closed, the male sways gently for a short while to settle the eggs, and both he and the female settle to the bottom again to take up their normal positions with their tails wrapped around their holdfasts. [read on]