HEALTH
Tiny Marine Worm Has Enormous Eyes That See As Well As Mammals
Michael Bok
A tiny, nocturnal worm that lives in the Mediterranean Sea has eyes so large that if a human had them, they would need a big sturdy wheelbarrow and brawny arms to lug around the extra 100kg [220 pounds], scientists say.
Vanadis bristle worms, also known as polychaetes, are tiny, transparent marine worms found around the Italian island of Ponza, west of Naples. Their eyes are so surprisingly large that scientists set out to determine how well they could see, and found they are as sharp as the eyes of mammals.
When neuro- and marine biologist Anders Garm from the University of Copenhagens Department of Biology heard from his colleague Michael Bok at Lund University how big the worm’s eyes are, he set other work aside to study them.
Together, we set out to unravel the mystery of why a nearly invisible, transparent worm that feeds in the dead of night has evolved to acquire enormous eyes. As such, the first aim was to answer whether large eyes endow the worm with good vision, Bok said.
It turned out the worm could use its eyes to see small objects and track their movements. Their study is published in the journal Current Biology.
It’s really interesting because an ability like this is typically reserved for us vertebrates, along with arthropods (insects, spiders, etc.) and cephalopods (octopus, squid). This is the first time that such an advanced and detailed view has been demonstrated beyond these groups. In fact, our research has shown that the worm has outstanding vision. Its eyesight is on a par with that of mice or rats, despite being a relatively simple organism with a miniscule brain, Garm said.
Now, researchers are turning their focus to what may have caused the species to evolve such advanced eyes.
“No one has ever seen the worm during the day, so we don’t know where it hides. So, we cannot rule out that its eyes are used during the day as well. What we do know is that its most important activities, like finding food and mating, occur at night. So, it is likely that this is when its eyes are important, Garm said.
Part of the explanation may be that their eyes are tuned to ultraviolet light, which is invisible to the human eye. That may indicate the worm’s eyes evolved to see their own bioluminescence at night, as a form of communication.
We have a theory that the worms themselves are bioluminescent and communicate with each other via light. If you use normal blue or green light as bioluminescence, you also risk attracting predators. But if instead, the worm uses UV light, it will remain invisible to animals other than those of its own species. Therefore, our hypothesis is that theyve developed sharp UV vision so as to have a secret language related to mating, Garm said.
It may also be that they are on the lookout look for UV bioluminescent prey. But regardless, it makes things truly exciting as UV bioluminescence has yet to be witnessed in any other animal. So, we hope to be able to present this as the first example, Garm said.
The fact that the worm, a fairly simple organism, has such complex eyes is also of interest to robotics researchers.
Together with the robotics researchers, we are working to understand how animals with brains as simple as these can process all of the information that such large eyes are likely able to collect. This suggests that there are super smart ways to process information in their nervous system. And if we can detect these mechanisms mathematically, they could be integrated into computer chips and used to control robots, Garm said.
Vanadis’ eyes may also hold clues to a burning evolutionary question: did eyes evolve just once, into every form we see today, or have they evolved multiple times independently?
Recent research has suggested multiple evolutionary origins for eyes, and the Vanadis’ eyes appear to be another piece of evidence for that theory. They have a simple design, but advanced functionality, and evolved in just a few million years, a short time evolutionarily speaking.
“This means that they must have developed independently of, for example, human eyes and that the development of vision, even with a high level of function, is possible in a relatively short time. Because, this worm is so young on an evolutionary scale, Bok said.
TMX contributed to this article.
