World First: Australian Scientists Spot The Ruby Seadragon In The Wild

Image: Della Vedova

A species of seadragon known only from museum specimens has been spotted in the wild for the first time by Aussie researchers.

The scientists used a remote-controlled camera to film the Ruby Seadragon, or Phyllopteryx Dewysea, at a depth of more than 50 metres - deeper than other seadragons go, and deeper than recreational Scuba divers can go.

That probably explains why the species hasn't been spotted until now, they say.

Researchers at Scripps Institution of Oceanography and the Western Australian Museum first described the species in 2015, from four specimens preserved in museum collections which had been misidentified as common seadragons.

Video footage of the ruby seadragon shows off its intense red colour and reveals that its habitat is very different from the algal reefs occupied by its relatives. The footage also reveals some striking differences between the three species.

"Until recently, no one had ever suspected a third species of seadragon existed," Professor Greg Rouse, Scripps Oceanography, lead researcher of the study said, "this discovery was made thanks to the great benefit of museum collections."

Its closest relatives, the leafy and common seadragon, inhabit much shallower depths of 3-25 meters. It also doesn't have 'leaves' on its body for camouflage, using its red colour to help hide it in the depths instead.

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

The researchers were also surprised to find that the ruby seadragon has a tail which it may use to hold on to objects to avoid being swept away by strong sea surge. Common and leafy seadragons cannot bend their tails, which raises questions about the evolution of tails in this group of organisms, according to the researchers.

Further study is needed to clarify whether the ruby seadragon has re-acquired a prehensile tail that was lost in a common ancestor, or if the absence of a prehensile tail in the common and leafy seadragons has independently evolved in each of the species.

"There are so many discoveries still awaiting us. Western Australia has such a diverse range of habitats," Nerida Wilson, Western Australian Museum, a coresearcher of the study said "and each one is deserving of attention."

To obtain their first live observations of the ruby seadragon, the researchers explored the Recherche Archipelago in Western Australia in April 2016. They were able to observe two ruby seadragons for nearly thirty minutes which yielded insights into the morphology, habitat, and behavior of the fish.

There remains a lot to understand about the ruby seadragon, such as whether it is facing any threats, or how widespread its distribution is. Researchers are only just beginning to understand how leafy and common seadragon populations are connected, and have much to understand about the newest member of the group.

[BioMed Central]

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