Subfamily Syngnathinae Higher classification Phyllopteryx | Phylum Chordata Genus Phyllopteryx Rank Species | |
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Similar Leafy seadragon, Pipefish, Phycodurus, Seahorse, Syngnathidae | ||
Common seadragon or weedy seadragon (Phyllopteryx taeniolatus) is a marine fish related to the seahorse. Adult common seadragons are a reddish colour, with yellow and purple markings; they have small leaf-like appendages that resemble kelp fronds providing camouflage and a number of short spines for protection. Males have narrower bodies and are darker than females. Seadragons have a long dorsal fin along the back and small pectoral fins on either side of the neck, which provide balance. Common seadragons can reach 45 cm in length.
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The common seadragon is the marine emblem of the Australian State of Victoria.
Range
The common seadragon is endemic to Australian waters of the Eastern Indian Ocean and the South Western Pacific Ocean. It can be found approximately between Port Stephens (New South Wales) and Geraldton, Western Australia, as well as Tasmania.
Habitat
The common seadragon inhabits coastal waters down to at least 50 m deep. It is associated with rocky reefs, seaweed beds, seagrass meadows and structures colonised by seaweed.
Biology
These fish are slow-moving and rely on their camouflage as protection against predation; they drift in the water and with the leaf-like appendages resemble the swaying seaweed of their habitat. They lack a prehensile tail that enables similar species to clasp and anchor themselves.
Individuals are observed either on their own or in pairs; feeding on tiny crustaceans and other zooplankton by sucking prey into their toothless mouths. Like seahorses, seadragon males are the sex that cares for the developing eggs. Females lay around 120 eggs onto the brood patch located on the underside of the males' tail. The eggs are fertilised and carried by the male for around a month before the hatchlings emerge. Seadragons, seahorses and pipefish are among the few known species where the male carries the eggs. The young are independent at birth, beginning to eat shortly after. Common seadragons take about 28 months to reach sexual maturity, and may live for up to six years.
Mating in captivity is rare since researchers have yet to understand what biological or environmental factors trigger them to reproduce. In captivity the survival rate for common seadragons is about 60%.
The Aquarium of the Pacific in Long Beach, California and the Tennessee Aquarium in Chattanooga, Tennessee in the USA, and the Melbourne Aquarium in Melbourne, Australia are among the few facilities in the world to have successfully bred common seadragons in captivity, though others occasionally report egg laying. In March 2012 the Georgia Aquarium in Atlanta, USA, announced a successful breeding event of common seadragons. As of July 2012, the Monterey Bay Aquarium has also successfully bred and hatched out baby common seadragons on exhibit.
Threats
The common sea dragon is classified as Near Threatened (NT) on the IUCN Red List 2006. While the common sea dragon is a desired species in the international aquarium trade, the volume of wild-caught individuals is small and therefore not currently a major threat. Instead, habitat loss and degradation due to human activities and pollution threaten common sea dragons most. The loss of suitable seagrass beds, coupled with natural history traits that make them poor dispersers, put the future of sea dragon populations at risk. This species is not at present a victim of bycatch or a target of trade in Traditional Chinese Medicine, two activities which are currently a threat to many related seahorse and pipefish populations.
Conservation
It is illegal to take or export these species in most of the states within which they occur. A database of seadragon sightings, known as 'Dragon Search' has been established with support from the Marine and Coastal Community Network (MCCN), Threatened Species Network (TSN) and the Australian Marine Conservation Society (AMCS), which encourages divers to report sightings. Monitoring of populations may provide indications of local water quality and seadragons could also become an important 'flagship' species for the often-overlooked richness of the unique flora and fauna of Australia’s south coast.
Captive breeding programs are in place for the weedy sea dragon, headed up by Sea Life Melbourne Aquarium. The dragon has been difficult to breed in captivity, though in 2015 research observing the creatures in the wild and trying to replicate the conditions in captivity had researchers making changes to the light, water temperature and water flow proving to be key. In December 2015 at the Melbourne aquarium had eggs hatch and the aquarium's weedy sea dragon population significantly increased, reporting in March 2016 that 45 fry were still going strong—an outcome which represents a 95 per cent survival rate.
Related species
The common seadragon is in the subfamily Syngnathinae, which contains all pipefish. It is most closely related to the other member of its genus, the ruby seadragon (Phyllopteryx dewysea), and also the leafy seadragon (Phycodurus eques). Haliichthys taeniophorus, sometimes referred to as the "ribboned seadragon" is not closely related (it does not form a true monophyletic clade with weedy and leafy seadragons).
The common seadragon was previously the only member of its genus until the discovery of the Ruby seadragon in 2015.
Ongoing research
In the November 2006 issue of National Geographic magazine, marine biologist Greg Rouse is reported as investigating the DNA variation of the two seadragon species across their ranges.