Monday, April 14, 2014

Leafy Sea Dragons and Their Amazing Adaptations

The leafy sea dragon, or Phycodurus eques, is a fascinating creature.  Although it sounds fierce, it is a small fish that has no teeth.  They can get up to 18 inches in length and normally live about 5 to 10 years.  They are only found in the southern coastal waters of Australia and they are listed as near threatened because many scientists believe that their species is becoming less common.  Part of this listing is due to the lack of research of their reproduction tendencies.  They thrive in the temperate reefs of Australia by hiding among the boulders, kelp, and seagrasses.  As mentioned before, they don't have teeth, so you must be wondering what their feeding strategy is.  Instead of biting their prey, they suck it down their long tube snout like a seahorse would.  Their diet is mainly composed of small invertebrates such as zooplankton and shrimp as well as larval fishes.  These small fishes must rely on their excellent camouflage to protect them from their predators.  As the name implies, they have many leaf-like protrusions all over their bodies.  This helps them to blend in with the seagrass and kelp in the reefs where they reside.  Their camouflage and color changing ability keeps them safe from their main predators, other fishes.

The above photographs show the amazing body structure of these organisms and their incredible ability to blend in with their surroundings.  Some research that is currently being done looks at their patterns of movement and habitat use.  In this study, 9 adult leafy sea dragons were tracked  near West Island, Australia using ultrasonic telemetry.  Leafy sea dragons lack a caudal fin and are weak swimmers.  Their leafy protrusions are not used for propulsion; they are only for the function of camouflage.  They use their small pectoral and dorsal fins to swim.  These fins are transparent and help them move to create the illusion of floating seaweed.

This research study had the four main goals of describing patterns of sea dragon movement, comparing the proportion of sea dragon positions over different habitats within the available habitats, determining the degree of movement or habitat use varies from day to night, and testing tagging effects on movement.  They found that all fish except one moved within a well defined home range of up to 5 ha. They determined this using the minimum convex polygon method.  They also found that there were long periods, up to 68 hours, of no movement and there were some short bursts of movement.  The fish were found to move about equally during the day and night.  There were no significant differences in movement based on tagging.  No fish were harmed in the removing of the transmitters, but the researchers did suggest that the lack of tagging effect may be due to the tags being attached to bony appendages, away from their bodies.  The sea dragons spent more time over Posidonia seagrass and less time over Amphibolis seagrass than expected.  This was concluded to be simply based on the area of habitat available.  This preference could be due to habitat selection or a response to factor such as prey abundance and water movement. There is still a lot of reproductive stately research that can be done on these organisms.  They are heavily protected just because there are not many of them.  Check out this quick video that summarizes some of their main features and characteristics!


Connolly, R. M., Melville, A. J. and Preston, K. M. 2002. Patterns of movement and habitat use by leafy sea dragons tracked ultrasonically.  Journal of Fish Biology. 61: 684-695.


  1. I've always loved leafy sea dragons!! Their leafy appendages make them such interesting creatures. I was surprised to find out that they only live in the coastal waters of Australia. Since they are similar to seahorses, and seahorses have a much wider range, I would have assumed that the sea dragons would too. Do you know how long they have been listed as being near threatened?

  2. I always thought that these were a type of sea horse! I'm glad I finally know for sure. I think their camouflage ability is unbelievable. I would love to see how their "leafy" appendages have changed ancestrally to become the master of disguise it is today.

  3. Great question! I also found it interesting that they had such a small range. They have been listed as near threatened since 2001.

  4. How their appendages have changed would be a great topic for continued research.

  5. I think that the camouflage that the leafy sea dragon exhibits is really cool! It is a shame that they are endangered because of their use in alternative medicine and the impacts that we have. Since they are such weak swimmers do you know how strong of a current they are able to withstand when they are swimming before they are carried away?