Common sea dragons are endemic to the waters off of the southern coast of Australia.
They can be found in several habitats including 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 °C (54 and 73 °F), and 10 to 50 meters (33 to 164 feet) deep, although they most often are found between 8 and 12 meters (26 and 39 feet) deep.
The lifespan of a common seadragon is up to 10 years.
A common seadragon reaches 45 centimeters (18 inches) in length and has a narrow body with a long, tubular snout.
Common seadragons are a reddish color, 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.
They have a long dorsal fin along the back and small pectoral fins on either side of the neck, which provide balance.
Seadragons usually live a solitary life, but males and females pair up to breed.
They are not sessile, but they are not very good swimmers, either. Because they are poor swimmers, each year a number of individuals are found washed ashore on the beaches of southern Australia.
Common seadragons do not have teeth or a stomach; therefore they eat almost constantly while covering wide areas searching for prey. They feed on mysid shrimp, a favorite food, and other small crustaceans, plankton, and larval fishes. They swallow their prey whole, creating suction to suck the food item into their small mouth by expanding a joint on the lower part of their snout. This feeding technique is similar to how a pipette works.
Like seahorses, seadragon males are the sex that cares for the developing eggs.
The male sea dragon incubates the fertilized eggs in a specialized spongy textured brood patch on the ventral surface of his tail. This area is composed of small cup-like indentations which each hold a single egg laid there by the female. The approximately 250 eggs remain attached until they hatch 4 to 6 weeks later. Sea dragons are completely independent upon hatching. The young feed on the remaining yolk sac and then graduate to consuming zooplankton.
The common seadragon is classified as “Least Concern” on the IUCN Red List of Threatened Species.
While the common seadragon 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 seadragons most.
The common seadragon is most closely related to the other member of its genus, the ruby seadragon (Phyllopteryx dewysea), and also the leafy seadragon (Phycodurus eques)
The common seadragon is the marine emblem of the Australian State of Victoria.