Although the visible light-sensitive opsins in ME photoreceptors have now been characterized, the functional relevance of visible light photoreception
in MEs remains largely a mystery (see Introduction).
Several theoretical estimates of brightness perception based on scotopic [Berman and others, 1990; Berman, 1992; Berman and Liebel, 1996] or cirtopic photoreception
[Berman, 2008] are shown in Fig.
and circadian entrainment in nonmammalian vertebrales.
It has been also suggested that cytochrome c oxidase and certain dehydrogenases may play a key role in the photoreception
process, particularly in the near infrared (NIR) frequency range .
In most phyla, although simple photoreception
is almost universally present, no eyes evolved, but eyes evolved later in Annelida, Mollusca, Onychophora, and Chordata.
Visual topics include a model of the propagation of visual signals, color discrimination, visual communication is Elasmobranchs, perceptions of like fish, UV communication, pigments in deep water, spectral sensitivity, and photoreception
without images while those on electric communication include measuring and visualizing fields, plasticity of the electric organ discharge waveform, evolution of signals, social signals during courtship, integration with other senses and the neuroethology of senders and receivers.
Circadian organization and photoreception
in an Australian dasyurid marsupial (Sminthopsis macroura).
In non-mammalian vertebrates including birds, reptiles, fish and amphibians there is another method of control of circadian responses by extra retinal photoreception
in which light directly impacts on the brain instead of indirectly via the retina and the nerves which supply the pineal gland as in mammals.
A recent study in onychophorans found arthropsin expression in the neural tissues of the central nervous system (CNS) but not in the eyes, suggesting that arthropsins may be involved in extraocular photoreception
(Eriksson et al.
However, in complex multicellular organisms, not all cell types have the necessary sensory capabilities, such as photoreception
, to entrain the circadian oscillator.
Recently, there has been a paradigm shift in the understanding of photoreception
for circadian, neuroendocrine, and neurobehavioral responses in humans.
Rhabdomeric photoreceptors are known to achieve photoreception
only via [G.