Friday, 13 January 2017

A scientific expedition off the coast of Western Australia led to researchers from The University of Western Australia, the Western Australian Museum and Scripps Institution of Oceanography catching a rare glimpse of the newly discovered ruby seadragon in the wild.

After several days of searching with a mini-remotely operated vehicle in waters more than 50 meters deep, the researchers caught the first-ever field sightings of the fish near Western Australia’s Recherche Archipelago.

As they observed two ruby seadragons on video for nearly 30 minutes, the scientists uncovered new details about their anatomy, habitat, and behaviour.

This latest discovery of the fish in the wild confirmed that ruby seadragons lack ornate leaf-like appendages, a feature that scientists have long considered to be distinguishing characteristics of all seadragons based upon the two known species—common and leafy seadragons. Both species use their leaf-like appendages as camouflage in the lush seaweed and kelp meadows where they prefer to live.

Last year, Scripps Oceanography marine biologists Josefin Stiller and Greg Rouse, and Dr Nerida Wilson of the Western Australian Museum and The University of Western Australia described the previously unknown ruby seadragon from preserved specimens misidentified as common seadragons—one of which was collected nearly one hundred years ago.

Using the preserved specimens, the researchers were able to assemble a rotating 3-D model of the new seadragon using a CT (computer tomography) scan of 5000 X-ray slices. This is when the lack of elaborate appendages common to all other seadragons first stood out to them.

To determine if the fish truly lacked appendages, or if the museum specimens had lost them prior to or during the collection process, the researchers partnered with a remote operated vehicle (ROV) company to help observe the new species in its natural environment, which is too deep for regular scuba diving.

From the new observations, the researchers suggest that ruby seadragons may use their curled tail to hold on to objects in the high-surge waters where they are found.

During encounters with the fish, the researchers also observed it fed by striking at prey, a behaviour common to the species.

These observations of the species in the wild confirmed the fish’s ruby red colouring and that their habitat lacks kelp and seagrass, but instead is dominated by sponges, once considered an undesirable habitat for seadragons.

The researchers believe the ruby seadragon lost its appendages through evolution, and that its red colour acts as a camouflage in the deeper dimly lit waters where it lives. Whether they evolved a curly tail independently from their pipefish ancestors, or simply retained it while the other seadragons lost it, will require further study.

Dr Nerida Wilson from UWA and the Western Australian Museum said there are so many discoveries still awaiting us in southern Western Australia.

“Western Australia has such a diverse range of habitats, and each one is deserving of attention,” Dr Wilson said.

In hopes of safeguarding the new species from overfishing, the research team recommends that the ruby seadragon be protected as soon as possible.

Media references

Mara Pritchard (Western Australian Museum)                                                             (+61 8) 6552 7803

Jess Reid (UWA Media and Public Relations Adviser)                                                   (+61 8) 6488 6876


Media Statements — Research — Science — University News
Oceans Institute — School of Biological Sciences