Animal Diversity Web

Ge­o­graphic Range

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)

• Biogeographic Regions
• australian
  • native

Habi­tat

Phyl­lopteryx tae­nio­la­tus 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
• reef

Phys­i­cal De­scrip­tion

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

Re­pro­duc­tion

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)

Be­hav­ior

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)

• Key Behaviors
• natatorial
• motile

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

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.

Con­ser­va­tion Sta­tus

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)

• IUCN Red List

  Near Threatened
  More information

• IUCN Red List

  Near Threatened
  More information

• US Federal List

  No special status

• CITES

  No special status

Other Com­ments

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

Con­trib­u­tors

Anna Fros­tic (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

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.