First live ruby seadragon spotted in Western Australia

By Karl Gruber 13 January 2017
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Live ruby seadragons have been recorded for the first time ever in the waters of the Recherche Archipelago, off Western Australia.

FOR THE FIRST time, scientists have caught a glimpse of living ruby seadragons, a species identified only two years ago in a museum collection.

In early 2015, researchers from the Western Australian Museum (WAM) in Perth and the Scripps Institution of Oceanography in California first discovered the ruby seadragon. The new species was hidden within the collections at WAM for over a century, disguised as a common seadragon.

Morphological and DNA analyses of four museum specimens led to the identification of the ruby seadragon species (Phyllopteryx dewysea), only the third known seadragon species in the world.

“Until recently, no one had ever suspected a third species of seadragon existed. This discovery was made thanks to the great benefit of museum collections,” said Professor Greg Rouse, from the Scripps Institute, lead author of the new study, published today.

Now, a team from WAM and Scripps have ventured into the realms of this iconic fish in the Recherche Archipelago, near Esperance, where they had the first recorded glimpses of two wild specimens.

ruby seadragon

The ruby seadragon was discovered to be a distinct species from museum specimens two years ago. (Image: Scripps Oceanography/UC San Diego)

Using a mini remotely operated vehicle, it took scientists a few days to find the tiny dragons, each measuring about 250mm in length. The two seadragons were found swimming in waters over 50m deep, well beyond the limits of recreational scuba diving, and researchers think this is why the species went undiscovered for so long.

The two specimens were filmed for about 30 minutes, revealing new details about their anatomy, habitat and behavior. For instance, scientists confirmed the lack of leaf-like appendages in this species, a signature characteristic of the common and leafy seadragon. They also observed a prehensile tail, not found in their seadragon relatives, but common on some far relatives such as the seahorse or pipefish.

“It was really quite an amazing moment when we discovered that the ruby seadragon lacks appendages. It never occurred to me that a seadragon could lack appendages because they are characterised by their beautiful camouflage leaves,” said Scripps graduate student Josefin Stiller, a co-author of the new study.

These leafy appendages help the common and leafy seadragons camouflage within the sea grass and kelp meadows where they live. However, there is no kelp or seagrass where the ruby seadragon lives, so such appendages would serve no purpose and researchers argue that the loss of its leafy appendages occurred through evolution, which also led to its red colouration, which serves as a camouflage in the deep, dimly lit water where this fish lives.

As for the prehensile tail, researchers think it may help the species hold on to objects in the mist of strong sea currents found in their habitat.

Overall, the finding hints at the great diversity still out there in Australian waters, waiting to be found.

“There are so many discoveries still awaiting us in southern Australia,” said Wilson, a co-author of the study. “Western Australia has such a diverse range of habitats, and each one is deserving of attention.”