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The leafy sea dragon, Phycodurus eques, is a marine fish related to the seahorse. It is the only member of the genus Phycodurus. These creatures are found around southern and western Australia and generally remain in shallow, temperate waters. Their name comes from their appearance, with long leaf-like protrusions coming from all over the body. These protrusions are not used for propulsion; they serve only as camouflage. The leafy sea dragon propels itself by means of a pectoral fin on the ridge of its neck and a dorsal fin on its back closer to the tail end. These small fins are almost completely transparent and difficult to see as they undulate minutely to move the creature sedately through the water, completing the illusion of floating seaweed.
Description
Much like the seahorse, the leafy sea dragon's name is derived from its resemblance to another creature (in this case, a mythical sea monster from Irish legends, called the "Cler"). While not large by sea monster standards, they are very large for sea horses, growing at least 18 inches (45 cm). They feed on plankton and small crustaceans.
The lobes of skin that grow on the Leafy Sea Dragon give it the appearance of seaweed, allowing it to camouflage with its surroundings. Its leafy appearance also allows it to appear to move through the water like a piece of floating seaweed. The Leafy Sea Dragon can also change color to blend in, but this ability relies on the sea dragon's diet, location, and stress levels.
The Leafy Sea Dragon has a long, pipe-like snout that it uses to feed. It primarily eats crustaceans including plankton and mysids, but its diet also includes shrimp and other small fish. It catches its prey using its camouflage ability. Leafy sea dragons oddly enough do not have teeth, which is rare amongst animals that eat small fish and shrimp.
The Leafy Sea Dragon is a cousin of the pipefish and belongs to the family Syngnathidae, along with the seahorse. The Leafy Sea Dragon differs from the seahorse in its appearance, form of locomotion, and the Leafy Sea Dragon's inability to coil or grasp things with its tail. A related species is the weedy sea dragon, which is multi-coloured and grows weed-like fins and can be much smaller than the leafy sea dragon. In the November 2006 issue of National Geographic magazine, marine biologist Greg Rouse is reported as investigating the DNA variation of the two sea dragon species across their ranges.
The leafy sea dragon is the official marine emblem of the state of South Australia. A biennial Leafy Sea Dragon Festival is held by the District Council of Yankalilla, South Australia. It is a festival of the environment, arts and culture of the southern Fleurieu Peninsula, with a theme of celebrating the leafy sea dragon. The inaugural festival in 2005 attracted over 7000 participants and visitors. [1]
Reproduction
As with seahorses, the male Leafy Sea Dragon cares for the eggs. Females deposit eggs on the tail of the male where they grow to maturity. The female produces up to 250 bright pink eggs, then passes them on to the male's tail via a long tube. The eggs then attach themselves to a brood patch, which supplies them with oxygen. It takes a total of nine weeks for the eggs to begin to hatch, depending on water conditions. The eggs turn a ripe purple or orange over this period. After this period, the male pumps its tail until the infants emerge, a process which takes place over 24-48 hours. The male aids in the babies hatching by shaking his tail, and rubbing it against the seaweed and rocks. Once born, the infant sea dragon is completely independent from its parents, eating small zooplankton until large enough to hunt mysids. Leafy sea dragons take about one month to reach sexual maturity.[2]
Movement
The Leafy Sea Dragon uses the fins along the side of its head to allow it to steer and turn. However, its outer skin is solid, limiting its mobility.
Individual Leafy Sea Dragons have been observed remaining in one location for extended periods of time (up to 68 hours) but will sometimes move for extended periods. Tracking of one individual indicated it moved at up to 150m per hour.[3]
Threats
Leafy Sea Dragons are subject to many threats, both natural and man-made. They are caught by collectors, and used in alternative medicine. They are vulnerable when first born, and are slow swimmers, reducing their chance of escape from a predator or other threat. They are also very fragile and thus are tossed around easily in storms, and can be ruptured by changes in water pressure.
They have become endangered through pollution and industrial runoff as well as collection by fascinated divers who are entranced by their unique appearance. In response to these dangers they have been officially protected by the Australian government.
Habitat
The Leafy Sea Dragon is found only in the waters of Australia from Kangaroo Island on the Southern shoreline to Jurien Bay[4] on the Western shoreline. It was once thought to be very limited in its range; however, further research has discovered that the sea dragon will actually travel several hundreds of meters from its habitat, returning to the same spot using its strong sense of direction. Leafy Sea Dragons are found around clumps of sand in waters up to 50 meters deep, hiding among rocks and sea grass.
In captivity
Sea dragons are protected by Australian law. Obtaining them is often an expensive and difficult process as they must be from captive bred stock, and exporters must prove their broodstock were caught before collecting restrictions went into effect, or that they had the correct licenses to collect them. To date, no successful, closed cycle, captive-breeding program has occurred (ie getting a generation of captive-raised sea dragons to breed). Sea dragons have a specific level of protection under fisheries legislation federally and in most Australian states where they occur, such that it is illegal to take or export them without a permit.
They are very fragile and unstable outside their natural habitats. Success keeping them has been largely in the public aquarium sector, due to funding and knowledge that would not be available to the average aquarium enthusiast.
References
- ^ "Leafy Sea Dragon Festival". Community events. District council of Yankalilla (29 September 2008). Retrieved on 2008-10-13.
- ^ "Life History of the Weedy Sea Dragon". Research. Sydney Institute of Marine Science (9 September 2008). Retrieved on 2008-10-13.
- ^ "Patterns of movement and habitat use by leafy seadragons tracked ultrasonically.". Journal of Fish Biology (Oxford: Blackwell) (61): 684-695.. 2002.
- ^ Morrison, Sue; Storrie, Ann (1999). Wonders of Western Waters. Como, Western Australia: Department of Conservation and Land Management. pp. 112. ISBN 0 7309 6894 4.
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