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Phycodurus equesGlauert's sea-dragon(Also: Leafy Seadragon)

By Martha Carlson

Geographic Range

Phycodurus eques (leafy seadragon), or Phycodurus eques as it is also known, lives in temperate waters exclusively off the southern coast of Australia as does its nearest relative, Phyllopteryx taeniolatus (weedy seadragon) (Dragon Search 2000; Wheeler 1975).

Habitat

Living at depths of 5 to 15 meters, P. eques resides in areas with clear water, lower light conditions, and prominent vegetation. Such areas include seagrass meadows, seaweed beds, and rocky reefs (Dragon Search 2000; Groves 1998).

Physical Description

P. eques can grow to be 50 cm but averages 30 cm in length (Dragon Search 2000; Groves 1998; Zahl 1978). Typical of Syngnathidae, P. eques exhibits a series of hard, exoskeletal rings around its entire body and a toothless tube-like snout (Groves 1998). Broad, flat appendages resembling seaweed branch from the plates surrounding the body (Groves 1998). Amidst these appendages on the sides of the body are several sharp spines that aid in defense against predators (Dragon Search 2000). The frond-like appendages and thin body vary on adults from green to yellow-brown to light brown; some have thin white lines radiating from the eye and extending over the body (Dragon Search 2000; Wheeler 1975). Color variation occurs and depends on age, location, diet, and environmental stressors (Dragon Search 2000).

Reproduction

Unlike most fish species, in P. eques the male incubates the eggs. The female develops between 200 and 300 eggs. Concurrently, the male forms many capillaries on the tail, which then proceeds to swell, wrinkle, and form about 120 eggcups (Dragon Search 2000). The eggs are then transferred from the female onto the male's tail and fertilized, although little is known exactly how this occurs successfully (Groves 1998). Four weeks is the average incubation period, and hatching occurs over several days to maximize survival rates (Dragon Search 2000; Zahl 1978). For the first few days, a yolk sac provides nutrients. Soon after birth, the newborns are able to swim and hunt successfully. P. eques is approximately 20 mm at birth and grows to 20 cm within one year (Groves 1998). Between one and two years, the fish reaches maturity and can live for seven years in captivity (Groves 1998; Dragon Search 2000). Much of the reproduction, such as yearly breeding frequency, is yet unknown (Groves 1998).

Behavior

P. eques moves very slowly through the water and mimics seaweed, which makes it a master at camouflage. Those predators not fooled by its blending capabilities are often surprised by its bony exterior and long, sharp spines (Zahl 1978). The species tends to swim alone or in pairs (Groves 1998).

Communication and Perception

Food Habits

Mimicking surrounding vegetation, P. eques is able to quietly approach its unsuspecting prey (Groves 1998). The fish uses suction to draw food into its mouth, which it opens by expanding a joint on the lower snout. The major staple to the diet of P. eques is mysid shrimp. Plankton and larval fishes, however, are also part of its diet (Dragon Search 2000).

Economic Importance for Humans: Positive

P. eques has traditionally been of economic importance to the aquarium fish trade. Due to its ornamentation, it is a desirable aquarium fish although difficult to maintain (Zahl 1978). This species also intrigues divers as it is very difficult to spot, and it is one of the many exotic Australian fishes that draw tourists from all parts of the globe (Groves 1998).

Conservation Status

Populations of P. eques have been declining due to both habitat destruction and aquarium harvest. Many conservation efforts including diver education, research efforts, and habitat preservation are currently underway in Australia to protect this species from decline (Dragon Search 2000).

Contributors

William Fink (editor), University of Michigan-Ann Arbor.

Martha Carlson (author), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

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.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

reef

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.

tactile

uses touch to communicate

References

Dragon Search, 2000. "Dragon Search Information Brochure" (On-line). Accessed October 30, 2000 at http://www.dragonsearch.asn.au/brochure/brochure.html.

Groves, P. 1998. Leafy Seadragons. Scientific American, 179: 85-89.

Wheeler, A. 1975. Fishes of the World: An Illustrated Dictionary. NY: Macmillan Publishing.

Zahl, P. 1978. Dragons of the Deep. National Geographic, 153: 838-845.

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