By Edie Widder, Ph.D., CEO and Senior Scientist - Ocean Research & Conservation Association (ORCA)
June 16, 2019
Trying to imagine what life is like for animals inhabiting the deep ocean is an enormous challenge. Because so many have fantastic eyes, it’s evident that vision plays a major role in their existence. And the light they have evolved to see – living light, called bioluminescence – is apparently equally fantastic. There are built-in flashlights for finding food, glowing lures for attracting prey, sexually dimorphic (i.e., different in males and females) light organs for attracting mates, nozzles that can squirt light into the eyes of an attacking predator, exquisite optical structures on the bellies of many fish, squid, and shrimp that can function as camouflage and a plethora of light organs with no known function. How can we ever hope to find out how all these extraordinary lights are used?
The trick is to be able to observe unobtrusively. That’s what the Medusa is designed to do. By illuminating with red light that most deep-sea inhabitants can’t see and using an optical lure that imitates a common bioluminescent jellyfish, it aims to attract and see the previously unseen.
A very large deep-sea shrimp (Nematocarcinus) inspects the e-jelly. Video courtesy of Edie Widder and Nathan Robinson. Download largest version (mp4, 8.1 MB).
A slickhead (Alepocephalidae) tentatively identified as Bathytroctes macrolepis inspects the e-jelly. These fish are rarely caught in trawls. Video courtesy of Edie Widder and Nathan Robinson. Download largest version (mp4, 4.1 MB).
For the first two deployments of the Medusa during this expedition, we put out more than a mile of line (1,830 meters;~6,000 feet), making these the deepest such observations ever made. Even at such an extreme depth, far below where the last traces of sunlight disappear around 1,000 meters (3,280 feet), we saw evidence of the importance of vision as we observed very large shrimp and fish attracted to the e-jelly. And on the third deployment, to 1,464 meters (0.9 miles), we recorded a shrimp spewing bioluminescence. As far as we know, this is the first time that behavior has ever been recorded in situ.
A shrimp bumps into the Medusa and executes an escape response that includes spewing bioluminescence. Video courtesy of Edie Widder and Nathan Robinson. Download largest version (mp4, 5.4 MB).
With each recovery of the Medusa, we haul the line in anticipating the opportunity to see some new, previously unseen aspect of what life is like for the creatures that inhabit the largest living space on our planet.
