This week we’re exploring a fascinating Australian coastal fish, the introverted Leafy Sea Dragon. That’s right, you read that correctly, “fish”!
Amazingly, Leafy Sea Dragons are actually fish. They have small, transparent fins; a dorsal fin on the back and pectoral fins on the neck. These help the dragons move through the water. They also have a bony skeleton. (In fact, its spine is why it is classified as a vertebrate.) Instead of scales their slender trunks are protected by a bony plates. And, they breath under water with tiny gills.
Despite having dorsal and pectoral fins, leafy sea dragons lack a caudal fin on their tails to help with propulsion. This means they can’t swim very well. Instead, their swim bladder holds gas that allows them to float in place. Sometimes they will rock back and forth amongst the seaweed, kelp beds, and sea grasses. Unlike their sea horse brethren, sea dragons do not have prehensile tails (tails that can grip on to things). This means they can be tossed about by rough waters or other fish.
Life Cycle, Reproduction, and Society
One of the most amazing things about leafy sea dragons, and other pipefish species, is that the father carries the eggs. Unlike sea horses, who carry eggs in a pouch, leafy sea dragons have a soft, spongy brood patch under their tail. In Summer, when the male is ready to mate he’ll turn bright yellow. The female sea dragon then lays about 200 bright pink eggs on the male’s brood patch where they become fertilised. Daddy dragon then carries the young for four to six weeks. When the babies are ready, they begin to hatch over several days. The father helps this process by gently shaking the babies from their eggs.
When the babies first hatch they are just 20mms long. Sea dragons live rather solitary lives and adult sea dragons don’t care for their young, so the babies are on their own in the dangerous waters. Because they are so small they can be picked off by predators. Only about one in twenty young survive. In their first year they’ll grow to about 20cm in length. By two years of age they are fully grown. Adults sea dragons will be between 30cm and 50cm in length. In captivity, leafy sea dragons only live about two to three years. In the wild, there are reports of sea dragons as old as seven and it is estimated that perhaps their average life expectancy is five to ten years.
Newly hatched leafy sea dragons feed from a yolk sac for the first few days of life. When they are big enough, they begin hunting zooplankton, such as copepods (a microscopic crustacean) and rotifers (tiny aquatic animal). As they mature they begin eating larger zooplankton, such as mysids (a tiny crustacean) and sea lice (the larvae of jellyfish and other ocean stingers). A leafy sea dragon hunts its food by snapping its head forward and sucking the shrimps and larvae into its long, tubular, toothless snout before swallowing them whole. They eat up to 1000 little sea creatures a day!
Habitat and Distribution
Leafy Sea Dragons have been recorded at depths of about 20-30 meters off the southern coasts of Western Australia, South Australia, and Victoria. They make their home near rocky reefs and sandy meadows where seaweed, kelp, and sea grasses grow.
One of the most fascinating things about leafy sea dragons is how effective they are at hiding. They look like the leafy kelp where they make their home. Other animals mistake them for kelp when they’re floating in the water among the macroalgae (seaweeds). But, not only do they blend in because of their shape, they can also change colour to match their surroundings. This amazing camouflage keeps them safe from carnivorous fish. Young sea dragons are less effective at camouflage and are sometimes preyed upon by other fish, crustaceans, and sea anemones.
Threats, Protective Status, and Conservation
Despite their amazing camouflage, which protects them from predators, sea dragons are still in danger. Because of limited distribution and threats to their habitat, leafy sea dragons are a protected species. On the IUCN Red List of Threatened Species the leafy sea dragons are given a status of Near Threatened. Rough waters can harm them because they cannot swim well or cling to coral. Swift currents or stormy waters can carry them into rocks and up onto beaches.
Humans are also a danger. Sometimes leafy sea dragons are caught up in commercial fishing or illegally captured as pets. Pollution, water quality, and the loss of sea grasses has decreased the habitable areas where sea dragons make their homes. Unfortunately, there is not enough data so we don’t know how well societies of sea dragons are withstanding these threats. What we do know is that it is very likely sea dragons should be considered endangered as they nearly meet the criteria for that rating and it is a lack of data that prevents the IUCN giving them a more accurate rating.
Time for some questions!
Are there other kinds of sea dragons?
- Yes! The Weedy Sea Dragon (Phyllopteryx taeniolatus) shares a lot of the traits of the leafy but has fewer leafy fronds.
What’s the difference between a sea dragon and a sea horse?
- While very closely related to sea horses, leafy sea dragons differ in a number of ways.
- Appearance: Leafy sea dragons have distinctive leafy fronds on their bodies.
- Movement: Sea dragons have limited movement and tend to float and sway. Sea horses can flap their dorsal fins 30-70 times a second to propel them through the water.
- Carrying Eggs: Male leafy sea dragons carry their young on a brood patch whereas male sea horses carry their young in a pouch.
- Prehensile Tail: Sea horses have a distinctive tail that can coil and grasp allowing the sea horse to grip onto objects.
- Kaylie says: “Also, sea dragons are not horses, they are dragons, and therefore better.”
Ask your own!
- Do you have a question about leafy sea dragons that isn’t answered here? Ask your question in the comments below and we’ll see if we can help you find the answer!
If you love marine animals, our Monthly Colour In Competition features the wonderful marine animal colour ins, including this trio, Lolly, Lizzie, and Laura Belle, the leafy sea dragon sisters from P.I. Penguin and the Case of the Missing Bottle. Grab your pencils, crayons, or crafty things and enter the competition for your chance to win any of our P.I. Penguin books!
Want to know more?
While we were learning about leafy sea dragons we came across some excellent resources and references.
To learn more about leafy sea dragons Near Threatened status, visit the IUCN Red List of Threatened Species:
If you love visuals, watch these fascinating videos:
A great fact-filled segment from Epic WildLife. (2 minutes)
A cute sing-song with basic facts to introduce young children. (2.5 minutes)
A series of very short videos including a two cool videos of leafy sea dragons eating and a fantastic one of leafy sea dragons hatching! (4 minutes – 6 videos ranging from 0:16 to 1:16)
A longer documentary that explores leafy sea dragons in depth. (44 minutes)
And for primarily text based learning, here are some great articles and brochures:
http://www.arkive.org/leafy-seadragon/phycodurus-eques/ (fantastic photographs!)