Leafy Sea Dragon

Anyone who has seen a leafy sea-dragon (Phycodurus equus) cannot fail to make the connection between this tiny gossamer-like creature and the dragons of fairy tales.

This rare and vulnerable relative of the sea-horse might be only around 45 centimetres long and live in an element foreign to its fierce mythical cousin, but in appearance it is unmistakably a dragon.

Sea-dragons actually belong to the same family as sea-horses (Sygnathidae) but differ in appearance from the latter by possessing leaf-like appendages on their head and body, and having a tail that cannot be coiled up.

Unique to the southern waters of South Australia, the leafy sea-dragon's home is inshore areas of seagrass. Unfortunately these are under increasing threat from pollution and excessive fertiliser run-off.

This is not the only danger faced by the sea-dragon. Although having no known predators amongst the marine world, it has become the target of unscrupulous 'collectors' who have denuded the more accessible seagrass areas of this amazing creature.

In 1991, the Australian Department of Fisheries, concerned by the rapidly decreasing numbers of the leafy sea-dragon, declared it a totally protected species.

The sea-dragon is poorly equipped for fleeing from those who wish to catch it. The outer skin or 'hide' of the sea-dragon is solid, limiting its mobility, and the only way it can propel itself along is through rapidly oscillating its ventral and dorsal fins.

However, it blends easily with the background and is agile enough to be able to hunt down tiny mysid shrimps or 'sea-lice', its main quarry. For those creatures, the sea-dragon has all the appearance of a mighty hunter.

Perhaps the most extraordinary thing about the leafy sea-dragon is that it is actually the male of the species which gets pregnant and gives birth. During mating, the female lays 100 - 250 eggs onto a special 'brood patch' on the underside of the male's tail, where they are attached and fertilised.

This brood patch, consisting of cups of blood-rich tissue each holding one egg, is especially developed by the male for use during the breeding season of August to the following March. The bright pink eggs become embedded in the cups of the brood patch, receiving oxygen via the cups' blood vessels.

During each breeding season, male leafy sea-dragons will hatch two batches of eggs.

After a period of about four to six weeks from conception, the male 'gives birth' to miniature juvenile versions of sea-dragons. As soon as a baby sea-dragon leaves the safety of its father's tail, it is independent and receives no further help from its parents.

For two to three days after birth, the baby sea-dragons are sustained by their yolk sac. After this, they hunt small zooplankton, such as copepods and rotifers, until large enough to hunt juvenile mysids.

The leafy sea-dragon is one of two species of sea-dragon found in Australia's southern waters. The common or weedy sea-dragon (Phyllopteryx taeniolatus) is less rare and can be encountered all the way from Port Stephens, New South Wales to Geraldton, West Australia.