Seadragons are delicate, armored fish living exclusively off southern Australia, and as the name suggests, they bear a striking resemblance to mythical fire-breathers. And there are only two species known, until now. Researchers studying specimens of the orange-tinted leafy seadragon and the yellow-and-purple common (or weedy) seadragon in museum collections have discovered a third, vividly red species: the spectacular ruby seadragon, Phyllopteryx dewysea. The findings, published in Royal Society Open Science last week, describe the first seadragon to be discovered in the last century-and-a-half.
An international trio led by Josefin Stiller of Scripps was analyzing DNA using tissue samples from the Western Australia Museum (WAM) when they discovered hints of a new species. They became certain of it after obtaining the complete specimen and the photographs taken shortly after the animal was collected. This 24-centimeter-long male carrying several dozen babies was trawled off the Recherche Archipelago at a depth of 51 meters (167 ft) in 2007. Since that’s unusually deep—the record for common seadragons is 33 meters (108 ft)—the team requested museum specimens that were collected on vessels and from depths of 50 meters (164 ft) or more, and they also combed through WAM’s collection.
These efforts turned up two ruby seadragons archived in the Australian National Fish Collection (one lived at a depth of 72 meters) and a fourth specimen, which had washed up on a Perth beach nearly a hundred years ago. “This new seadragon first entered the Western Australia Museum’s collection in 1919, and lay unidentified for almost a century,” study co-author Nerida Wilson of WAM says in a news release.
The team named it after Mary "Dewy" White, who supported the research. Pictured to the right, the Phyllopteryx dewysea on-deck shortly after being trawled and (a) preserved, with tip of tail and eggs removed for DNA extraction, and (b) 3D scans created with micro-computed tomography (c-f). Scale bars, 1 cm. Notice the 18 trunk segments and a pronounced arch (larger image here).
Mitochondrial markers of the new species differed from the common seadragon (Phyllopteryx taeniolatus) by 7.4 percent, and by 13.1 percent to the leafy seadragon (Phycodurus eques). That’s pretty similar to the 11.6 percent distance between those two previously known species. Click here to see a very cool comparison of the three skeletons. Furthermore, the coloration suggests it lives in deeper waters than other seadragons since red shading would be absorbed at depth, effectively serving as camouflage.
“A CT scan gave us 5,000 X-ray slices that we were able to assemble into a rotating 3D model,” Stiller explains. “We could then see several features of the skeleton that were distinct from the other two species, corroborating the genetic evidence.”
“It has been 150 years since the last seadragon was described and all this time we thought that there were only two species,” Wilson adds. “Suddenly, there is a third species! If we can overlook such a charismatic new species for so long, we definitely have many more exciting discoveries awaiting us in the oceans.” And in museum collections. The team is now putting together an expedition to find ruby seadragons living in the wild.
Images: Western Australian Museum (top), J. Stiller et al., Royal Society 2015 (middle)