Seahorse relatives
Essential facts about seadragons

Seadragons are related to seahorses, pipefish and other members of the family syngnathidae. Like seahorses they have chameleon-like eyes, a horse-like head, and a fused jaw. They feed by sucking tiny marine animals such as sea lice and mysid shrimp through these "snouts." Unlike seahorses, they swim in a horizontal position and the males do not carry their eggs in pouches, instead using a brood patch under their tails to transport them.

How many different kinds of seadragons are there?

There are two species: the leafy seadragon (Phycodurus eques) and the weedy seadragon (Phyllopterix taeniolatus). The word 'Phycodurus' is derived from two Greek words, 'phyco' meaning seaweed and 'durus' meaning tough or strong. 'Eques' is derived from the Latin word equus, which means horse. 'Phyllo' is Greek for 'leaf' and 'opteryx' means feather or wing. Interestingly, although there are only two species, they each have their own genus.

What do leafy and weedy seadragons look like?

Both leafy and weedy seadragons have similar body shapes to seahorses. They have heads characterised by long horse-like snouts and independently rotating eyes. 

Click the image to watch weedy seadragons disappear into their habitat. Video: Keith Martin-Smith/Project Seahorse

Leafy seadragons are adorned with a myriad of leafy appendages, from short, stubby twig-like protrusions to large, branching kelp-like lobes that drift and sway in the current. Couple this with their ability to change colour and hover through the ocean with almost imperceptible fins, and they are true masters of camouflage. You can watch a video of leafy seadragons disappearing into their habitat here:

Weedy seadragons have far fewer leafy appendages, which are more lobe-shaped and also help them blend well with the swaying grassy seaweeds of their underwater habitat. Weedy seadragons are generally more colourful than the weedy seadragons. They are usually redish in colour with yellow, red, orange and purple spots and stripes decorating their bodies. Like leafy seadragons and other syngnathids, they are masters of camouflage and these elaborate markings and appendages help break-up their outline so they can blend into the background.

How big are seadragons?

Both species are fairly large in terms of syngnathids, with adult leafy seadagons reaching a size of 20-24cm (8 – 10 inches) and adult weedy seadragons reaching a maximum of 45cm (18 inches) in length.

Where do seadragons live?

Seadragons are endemic to southern Australian waters, which means that they are found nowhere else on earth. They inhabit a wide variety of habitats including rocky reefs, sea grass meadows and seaweed beds.

Do seadagons use their ‘leaves’ for swimming?

The protrusions from seadragons are only used for camouflage only and not for locomotion. It may be hard to imagine how they swim with such reduced tails. Seadragons have modified pectoral fins just behind their heads as well as a modified dorsal fin on their lower backs. With these fins they are able to slowly move themselves through the water as they keep a look-out for prey and potential mates. 

Why do seadragons have such long noses?

A close-up shot of a leafy seadragon. Photo: Dave Harasti/daveharasti.com

This long nose is actually the mouth of the seadragon where the jaw has been fused into a long tube. This fused jaw is common between all syngnathidae and is the reason for the name of the group, with 'Syn' meaning fused and 'Gnathus' meaning jaw. This adaptation has turned the syngnathids into some of the fastest feeders in the animal kingdom! This long thin tube allows them to suck up tiny prey at an incredible speed. Couple this with the seadragons camouflage and they don’t need to hunt for their food, they simply wait for their food to swim past before quickly sucking them up into their ‘snout’ before the prey has a chance to escape. 

Do seadragons also have pouches?

Unlike seahorses, seadragons actually do not carry their eggs in pouches. Instead, male seadragons have a brood patch, which is a specialised area of skin on the underside of the tail designed to carry eggs. This brood patch consists of a series of tiny cups that hold the eggs while they are fertilised and also make sure the eggs get all the oxygen they need before they hatch. Much like seahorses, the male is responsible for caring for the eggs and the eggs produce fully developed young.

Further reading

 

Banner image of leafy seadragon pair courtesy of Dave Harasti/www.daveharasti.com