A New Dragon Among Us, Beware to the Lanternfish
|Dragonfish newly discovered Credit: HBOI|
The earth’s biological census currently lists around 28,000 species with a backbone–a relatively small number which now has a new addition. Dr. Tracey Sutton, a fish ecologist at the Harbor Branch Oceanographic Institution in Ft. Pierce, Fla., has discovered a new species in a bizarre and elusive family of deep-sea predatory fish known collectively as dragonfish. The find, reported in the current issue of the journal Copeia, is the first new dragonfish species discovered in more than a decade.
"The fact that we are still finding new species in one of the best-studied oceanic regions in the world tells us there is still a lot more out there to be known," says Sutton, who is also a leader in the ambitious international effort to identify all ocean animal and plant species known as the Census of Marine Life.
According to the World Wildlife Fund, the Earth is losing species at a rate not seen for 65 million years, since the extinction of the dinosaurs. The study of biodiversity and astrobiology share the common thread of viewing the planet as a whole and attempting to see its future by examining its past. The present moment in history has been characterized as the first time in which one species– humans– are in one way or another ‘responsible’ for the entire biosphere: changing it, maintaining it, and of course, possibly extinguishing it. As Harvard professor of evolutionary biology , Andrew Knoll, remarked: " [For astrobiology] everything we know about life in the universe comes from life on Earth. In a sense, putting current diversity at peril for those who would like to understand biology as a planetary phenomenon is like burning a library."
As the director of the Hayden Planetarium, Neil Tyson, wrote about the marvels of biodiversity: "I do not know whether biologists walk around every day awestruck by the diversity of life. I certainly do. On this single planet called Earth, there co-exist (among countless other life forms), algae, beetles, sponges, jellyfish, snakes, condors, and giant sequoias. Imagine these seven living organisms lined up next to each other in size-place. If you didn’t know better, you would be hard-pressed to believe that they all came from the same universe, much less the same planet".
The first specimen of the new species, dubbed Eustomias jimcraddocki, was large, compared to the average pencil-sized dragonfish at about six inches long and roughly the size of a hot dog. Sutton named it after Jim Craddock, a legend in the deep-sea fish biology field.
Sutton discovered the fish during an expedition to Bear Seamount, off New England, that was sponsored by the National Oceanic and Atmospheric Administration’s Office of Ocean Exploration. Now the head of Harbor Branch’s Fish and Plankton Ecology Department, he was at the time a Postdoctoral Scholar at the Woods Hole Oceanographic Institution in Massachusetts.
|Alien species, terrestrial biodiversity.|
Sutton plucked the new dragonfish from a net being used to sample the study area’s marine life. While identifying the catch on board, he realized that the specimen represented a new species. Later he traveled to the Smithsonian Institution and Harvard to do some fish sleuthing. In museum collections at those institutions, he found 13 additional specimens collected in the Atlantic over the past 30 years that had previously been either unidentified or misidentified. This work verified that the new species was in fact unique.
Dragonfish are so rare that scientists have often been forced to study and describe new species based on a single specimen. "I really wanted more than just one fish," says Sutton, "so I was relieved to find more."
As with all dragonfish, which live at depths ranging from about 600 to 3,000 feet, the new species has menacing teeth, and a mouth that can jut out to engulf prey as wide as it is. They also have small organs along their bellies that produce light, or bioluminescence, and that may serve as camouflage to make the fish blend in with faint sunlight from above, thus appearing invisible to potential predators below.
The distinguishing feature of dragonfishes is a long thin protrusion known as a barbel anchored at the fish’s chin that trails below its body. The barbels look like tree branches, and each species has a unique barbel pattern. At the end of the barbel is a bioluminescent organ the animals use like a fishing lure to attract prey, mainly lanternfish. If the barbels served only this function, scientists would expect all dragonfishes to have similar barbels. However, because the protrusions are so varied, some theorize the fish may also use them to identify other members of their own species for reproduction.
As astrobiologists speculate about diversity as one might imagine arising in unusual environments either terrestrially or on a distant, extrasolar planet, the discovery of new species in some of the most thoroughly studied places on Earth is noteworthy. As Tyson concluded: " Try describing a snake to somebody who has never seen one: "You gotta believe me. There is this animal on Earth that 1) can stalk its prey with infrared detectors, 2) swallows whole live animals up to five times bigger than its head, 3) has no arms or legs or any other appendage, yet 4) can slide along level ground at a speed of two feet per second!"
The new Dragonfish glows with biologically-produced light, camouflages itself against glinting sunlight to any prey below it, and uses its own fleshy fishing pole to lure another bizarre species, the lanternfish, to its death. The new species is apparently rare enough to individualize the pattern of this lure also to identify itself to the opposite gender for what must be rare encounters for reproduction.