Color at Night: Geckos can distinguish hues by dim moonlight
Susan Milius
Of all the vertebrates, a gecko has just become the first to ace behavioral
tests for seeing color in very low illumination.
People, for example, go color-blind in light equivalent to dim moonlight,
but helmet geckos, Tarentola chazaliae, don't. They can still tell a blue
from a gray of the same intensity, report Lina S.V. Roth and Almut Kelber,
both of the University of Lund in Sweden, in an upcoming Biology Letters.
Earlier physiology had shown that most vertebrates deploy two systems of
light-sensitive cells in their eyes. Two or more types of cone cells work
together to sense color in abundant light, and a single type of rod cell
detects light more sensitively, but only in black and white. Thus, when the
seeing gets tough, people forgo color vision and rely on their rods.
Lizards, however, lack rods, presumably because they evolved for a long period as strictly daytime creatures.
Copyright �2004 Science Service -------------------- Lyle Puente President Global Gecko Association
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