Poultry, Fisheries & Wildlife Sciences
Open Access

A Short Note on Leafy Seadragons

Han Xu^{* *}Correspondence: Han Xu, Department of Aquaculture, University of Plymouth, Drake Circus, Plymouth, United Kingdom, Email:

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Description

Phycodurus eques is also known as leafy seadragons which is particularly well camouflaged with elaborate, ornate skin filaments that hang from the head, body and tail making this animal virtually indistinguishable from the floating sea weed in which it lives. Usually green to yellow in color. The body is covered in protective jointed plates instead of scales and long, sharp spines line its dorsal edge. Leafy sea dragons are very poor swimmers and rely on their camouflage to avoid predation. They are relatively large compared to their closely related species and reach lengths of up to one foot (30 cm) long. Leafy sea dragons eat small, plankton crustaceans but are small enough themselves and have sufficient vision to see and attack individual prey (unlike large filter feeders). Their heads are relatively large compared to their very small mouths, so they are able to concentrate enough pressure at their mouths to easily suck in their prey.

Like in seahorses and pipefishes, male leafy sea dragons care for the fertilized eggs. They do not have a specialized pouch like male seahorses but instead carry the eggs under the tail. There, they remain exposed to the elements but safe, and the male provides them with necessary levels of oxygen through a specialized, nearby organ. Newly hatched leafy sea dragons receive no further parental care. They reach sexual maturity in approximately two years. The leafy sea dragon is a popular species in public aquaria and its trade is tightly regulated. There are very few people licensed to collect leafy seadragons, and a more significant threat to their populations comes from their accidental capture in fisheries targeting other species. Scientists consider this species to be near threatened with extinction. Without continued careful management of the human activities that affect leafy sea dragon populations, the species could become more seriously at risk of being lost.

Unlike seahorses, sea dragons do not have a pouch for rearing their young. Instead, the male carries the eggs fixed to the underside of his tail from where they eventually hatch. When male sea dragons are ready to receive eggs from the female, the lower half of the tail on the male appears wrinkled. During mating, females lay 100-250 eggs onto a special ‘brood patch’ on the underside of the male’s tails, where they are attached and fertilized. This brood patch, consisting of cups of blood-rich tissue each holding one egg, and is specifically developed by the male for use during the breeding season (August-March). The bright pink eggs become embedded in the cups of the brood patch, receiving oxygen via the cups’ blood vessels. During each breeding season, male leafy sea dragons will hatch two batches of eggs. After a period of about 6-8 weeks from conception, the male ‘gives birth’ to miniature juvenile versions of sea dragons. As soon as a baby sea dragon leaves the safety of their father’s tail, they are on their own. For 2-3 days after birth, baby sea dragons are sustained by their yolk sacs. After this, they hunt small zooplankton, such as copepods and rotifers, until large enough to hunt juvenile mysids. Sea dragons grow to a length of 20 cm after one year, reaching their mature length at two years. In the wild, young sea dragons are preyed upon by other fish, crustaceans and even sea anemones. Young sea dragons look more delicate, and are often differently colored than adults, and may hide in different types of seaweeds. The leafy sea dragon is a rare sight and a very fragile creature. Handling of any sort is discouraged due to the likelihood of injuring this animal. They do seem to enjoy having their picture taken though. Leafy sea dragons, Phycodurus eques, are listed as Near Threatened (NT) on the IUCN Red List of Threatened Species.