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Sea Dragon
Anyone who has seen a leafy sea-dragon (Phycodurus equus) on display at Aquarium WA (formally Perth's Underwater World)
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 WA and 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 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,
WA.
A FEW SEA-DRAGON FACTS
Leafy sea-dragons are sometimes found dead on the beach, washed up in a clump of seaweed after a storm. Their flotatin
bladders are very fragile and cannot cope with any sudden changes in water pressure or depth, such as might occur during bad
weather.
Aquarium WA (at Hillarys, Perth, Western Australia) is one of only three aquaria in the world to have legally and successfully
kept leafy sea_dragons on display. Any specimens illegally caught by amateurs usually die quickly because of their captor's
inability to provide them with the correct live food daily.
Threatened species often caught incidentally by shrimp trawlers
Larger, slower-growing species and top predators at risk
Sea turtles and seahorses known to be particularly vulnerable
Researched by wishintreeUK
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