Sea Dragons

A close up view of a leafy sea dragon. Image taken at the Monterey Bay Aquarium.

Sea dragons are these beautiful and bizarre fish that live off of the coast of Australia and are closely related to seahorses. There are two types of sea dragons-leafy sea dragons (shown above) and weedy sea dragons (shown below).

A weedy sea dragon floats by. Image taken at the Monterey Bay Aquarium.

As you can see, the leafy and weedy sea dragons have camouflage to match seaweed. I like to think of them as the vertebrate versions of  stick insects in the ocean. Just like stick insects matching the movement of branches in the wind, sea dragons will gently float in the water in a manner that matches the movement of the swaying seaweed.  The long leaf-looking branches coming off of their bodies are actually skin growths.

It’s a good thing their camouflage is so effective; these fish rely heavily on their ability to hide for protection. Sea dragons and their relatives, seahorses and pipefish, are incredibly slow swimmers. They are some of the slowest fish in the ocean. Some seahorses would take more than an hour just to swim across a swimming pool.

There’s a couple of reasons why the animals in this family are such slow swimmers. As you can see, it’s tail is not one that will help much when its trying to swim. No, instead of using their tails to push them along like most other fish, these animals have a so-thin-its-see-through fin on their back that ripples and moves them along slowly. In the picture below, you can actually see the rays of this fin.

A full view of a leafy sea dragon. Note the nearly invisible fins. Image taken at the Monterey Bay Aquarium.

But that’s not the only reason they’re so slow. Unlike other fish, sea dragons don’t have scales. Instead they have an armor-like skeleton made of plates and rings, covered in skin. This armor, while tough, bony and often unappealing to potential predators, is not very flexible.  So, getting away is no easy task for the sea dragons. While they do have a few spines they can protect themselves with, they’re better off just not being seen in the first place, and they are very good at that.

A leafy sea dragon. Image taken at the Monterey Bay Aquarium.

I suppose aside from their camouflage, the one thing sea dragons and relatives are most known for is how they produce young sea dragons. That is, in this family, it’s the males that get pregnant and carry the eggs. For sea dragons, the females will stick tiny pink eggs along the underside of the male’s tail (an area called the brood patch). He fertilizes them and then a cup forms around each of the eggs, through which oxygen is transmitted. By doing this, the males ensure paternity, thus eliminated a common problem for males in the animal kingdom. (I suppose it’s better than the stick insect’s way of just riding on top of the females for hours at a time.) Multiple females will attach their eggs to a male until his brood patch is completely full. When these eggs hatch, the young come out tail first and are just miniature versions of the adult.

I have been using images of the same leafy sea dragon, so I wanted to include at least one other, so you can see the variation. Individual sea dragons can change color as well. Here’s another one below:

A different leafy sea dragon. Image taken at the Monterey Bay Aquarium.

The patterns on their face are actually unique to each animal, so researchers and aquarists can use these markings to identify individuals. So look closely at this face. You’ll never see another one like it.