ABSTRACT
The first studies dealing with the teleost pineal organ emphasized its photoreceptive characteristics, and it soon appeared it was involved in the control of functions and behaviors displaying daily rhythms (for reviews see: Zachmann et al., 1992a; Ekström and Meissl, 1997; Falcón, 1999; Boeuf and Falcón, 2001). Indeed, the pineal epithelium contains photoreceptors cells that resemble the retinal cone photoreceptors, both, on a structural and functional point of view. The cone-like photoreceptors establish synaptic contacts with ganglion cells (or second order neurons) that send their axons to the brain. Interstitial cells make the third main cell type of the pineal epithelium, which so resembles to a simplified retina.
