Natures wonders: Single celled organism with eye? (Introduction)

by David Turell , Wednesday, July 01, 2015, 20:41 (3431 days ago) @ David Turell

A plankton with a nucleus and an eyelike structure. Fascinating:-http://www.sciencedaily.com/releases/2015/07/150701133348.htm-"Canadian Institute for Advanced Research senior fellows Brian Leander and Patrick Keeling supervised lead author Greg Gavelis at the University of British Columbia and, in collaboration with senior fellow Curtis Suttle, showed that this eye-like structure contains a collection of sub-cellular organelles that look very much like the lens, cornea, iris and retina of multicellular eyes that can detect objects -- known as camera eyes -- that are found in humans and other larger animals.-"The researchers gathered single cells of warnowiids off the coasts of B.C. and Japan, sequenced their genomes, and analyzed how the eyes are built using new methods in electron microscopy that allow the reconstruction of three dimensional structures at the subcellular level.-"They found that a layer of interconnected mitochondria, organelles that supply energy to cells, surrounds a robust lens and makes up the warnowiids's equivalent of a cornea. In addition, a network of interconnected plastids that originated from an ancient symbiosis with red alga radiate from the retinal body.-"Plastids have their own genome and are responsible for harvesting energy from light in photosynthetic plants and algae. The scientists determined that the retinal body contains a plastid genome suggesting components of the light-harvesting machinery may have been adapted to use in detecting light for sensory functions rather than to acquire energy.-"Scientists still don't know exactly how warnowiids use the eye-like structure, but clues about the way they live have fuelled compelling speculation. warnowiids hunt other dinoflagellates, many of which are transparent. They have large nematocysts, which Leander describes as "little harpoons," for catching prey. And some have a piston -- a tentacle that can extend and retract very quickly -- with an unknown function that might be used for escape or feeding.-"The team speculates that the eye-like structures help warnowiids detect their dinoflagellate prey and send chemical messages to communicate with other parts of the cell. Dinoflagellates have a uniquely large nucleus with tightly packed chromosomes that can change the polarization of light passing through them. One possibility could be that warnowiids can detect the light's orientation change as it passes through their transparent prey, showing them in which direction to hunt.-"'The internal organization of the retinal body is reminiscent of the polarizing filters on the lenses of cameras and sunglasses," Leander says. "Hundreds of closely packed membranes lined up in parallel.'"