Date: March 8, 2016
Source: Frontiers
The eyes of an
Australasian butterfly contain a record fifteen classes of light-detecting
photoreceptors, six more than any other insect and far more than necessary for
color vision.
When researchers studied
the eyes of Common Bluebottles, a species of swallowtail butterfly from Australasia , they were in for a surprise. These
butterflies have large eyes and use their blue-green iridescent wings for
visual communication -- evidence that their vision must be excellent. Even so,
no-one expected to find that Common Bluebottles (Graphium sarpedon) have at
least 15 different classes of "photoreceptors" -- light-detecting
cells comparable to the rods and cones in the human eye. Previously, no insect
was known to have more than nine.
"We have studied
color vision in many insects for many years, and we knew that the number of
photoreceptors varies greatly from species to species. But this discovery of 15
classes in one eye was really stunning," says Kentaro Arikawa, Professor
of Biology at Sokendai (the Graduate University for Advanced Studies), Hayama,
Japan and lead author of the study.
Have multiple classes of
photoreceptors is indispensable for seeing color. Each class is stimulated by
light of some wavelengths, and less or not at all by other wavelengths. By
comparing information received from the different photoreceptor classes, the
brain is able to distinguish colors.
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