A team of scientists at the University of British Columbia (UBC) discovered what seems to be an eye-like structure on single-celled marine plankton known as warnowiids.
According to the researchers, these predatory microbes bear a dark purple spot on their bodies called an ocelloid, which closely resembles the multicellular eye of other animals. It is believed that the warnowiids use this functional eye in order to spot organisms they intend to consume.
Greg Gavelis, a zoology Ph.D. student at UBC and lead author of the study, said the existence of this complex structure is interesting especially on a single-celled organism.
He said the ocelloid contains several sub-cellular organelles that resemble parts of multicellular eyes, such as the lens, iris, retina and cornea.
Despite the discovery of this eye-like structure on the warnowiids, the researchers have yet to identify how the tiny organisms use the ocelloid exactly.
These single-celled creatures are known to hunt transparent cells in the plankton using structures that appear like small harpoons.
Gavelis and his colleagues speculate that the ocelloid somehow helps the warnowiids detect sudden changes in light as it penetrates through the creatures' transparent prey. The eye structure would then send chemical signals to other parts of the cells to show them which direction the prey can be located.
UBC zoologist Brian Leander explained that the internal organization of the ocelloid's retinal component functions similarly to the polarizing filters found in most sunglasses and camera lenses. It is composed of hundreds of membranes closely packed together and arranged in a parallel line.
Finding a definitive answer as to how ocelloids exactly work remains an elusive task as of the moment because of the rarity of spotting warnowiids in the wild, and the aquatic organisms have yet to be grown in laboratories.
The specimens the researchers used for their study were collected off the coasts of Japan and British Columbia.
The UBC scientists studied the minute structure of the warnowiids' ocelloid using advanced microscopy technology found at the university's Center for High-Throughput Phenogenomics. The microscopes allowed the team to produce three-dimensional images of the eye structure at a subcellular level.
The University of British Columbia study is published in the journal Nature.
