Weedy sea dragons, also known as common sea dragons, are endemic to the waters off of the southern coast of Australia. Individuals of this species have been sighted off the eastern coast of Australia in New South Wales, as far north as Port Stephens; along the southern coast; and up around the western coast of Australia as far north as Geraldton, West Australia. (Dawson, 1985)
can be found in rocky reefs, sea weed beds, sea grass meadows, and kelp gardens. In all of these areas, their leafy appendages provide protection by means of camouflage against the sea weed. While this may seem like a broad range of habitat, sea dragons have very specific requirements. The water must be between 12 and 23 degrees Celsius, and 10-50 meters deep, although they most often are found between 8 and 12 meters deep. (Australian Museum, 1999)
- Aquatic Biomes
A weedy sea dragon reaches 45cm in length and has a narrow body with a long, tubular snout. It has two spines above its eye, one spine in front of the eye, and a varying number of leafy appendages, either paired or single, along its body. These purple appendages have a black border, and provide the fish camouflage in its habitat because they resemble floating seaweed. The bodies of these fish are usually red with yellow spots and seven purplish blue stripes near the head. Weedy sea dragons are not sexually dimorphic and have no subspecies, but do have a close relative: Phycodurus eques, the leafy sea dragon. The leafy sea dragon is found in the same geographic range, and differs in appearance only because it has many more appendages. (Scott, 1962)
- Other Physical Features
- bilateral symmetry
While it is not known at what age sea dragons reach sexual maturity, their reproductive strategies are well documented. Like their relatives the sea horses, the male sea dragons brood the eggs. When a male is ready to receive the eggs, which he indicates by wrinkling the lower half of his tail, the female deposits about 250 ruby colored eggs onto his brood patch. The brood patch is made of tiny cups of blood-rich tissue, and each cup holds and nourishes one egg. After eight weeks, the eggs hatch over a period of a couple days. After hatching, the young sea dragons spend two or three days in the yolk sac of the egg, where they continue to be nourished. After the young leave the yolk sac, they feed on copepods and rotifers, although only 60-120 of them will survive, while the others fall prey to sea anemones. The season of breeding is August through March, and during this time the males brood two batches of eggs. The young receive no parental care after they hatch because they are released into the external environment. (Dawson, 1985; Cronulla Dive Center, http://pixie.tig.com.au/~scuba/seadragon.html)
Common sea dragons are solitary animals that have no known predators. They are not sessile, but they are not very good swimmers, either. This is because their bodies are surrounded by protective dermal plates, which inhibit their mobility. Also, they lack a caudal fin, and therefore must rely on their ventral and dorsal fins for swimming. Because they are poor swimmers, each year a number of individuals are found washed ashore on the beaches of southern Australia. (Dawson, 1985)
Communication and Perception
Weedy sea dragons have no teeth, but instead feed by way of suction. Their pipe-like terminal mouth has an intricate system of bones pulled by muscles to create a strong suction force that is directed at food. Their prey include mysid shrimp, sea lice, and larval fish. (Scott, 1962)
Economic Importance for Humans: Positive
Members of this species have often been used in Asia as aphrodisiacs and other medicines. Also, many people go scuba diving off the coast of southern Australia specifically to see weedy sea dragons, which, therefore, promote tourism.
Economic Importance for Humans: Negative
This peaceful species does not in any way negatively affect the human species.
Weedy sea dragons are threatened by aquarium collectors and Oriental herbalists, who can sell their dried and powdered bodies for up to $200/gram. They are also killed by pollution and fertilizer run-off in their shallow, coastal habitats. Because of these threats, weedy sea dragons are a legally protected species in both New South Wales and Tasmania. (Australian Museum, 1999)
A couple beautiful pictures of a weedy sea dragon, and its relative the leafy sea dragon, can be viewed at http://www.austmus.gov.au/fish/focus/seadrag.htm
Anna Frostic (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
uses touch to communicate
Australian Museum, 1999. "Australian Museum Online" (On-line). Accessed March 15, 2000 at http://www.austmus.gov.au.
Cronulla Dive Centre, Accessed March 15, 2000 at http://pixie.tig.com.au/~scuba/seadragon/html.
Dawson, C. 1985. Indo-Pacific Pipefishes. Ocean Springs, Mississippi, USA: The Gulf Coast Research Library.
Hickman, C., L. Roberts, A. Larson. 2000. Animal Diversity. USA: McGraw-Hill Companies, Inc..
Scott, T. July, 1962. The Marine and Fresh Water Fishes of South Australia. Adelaide, Australia: W.L. Hawes, Government Printer.