THE OCULAR TAPETUM LUCIDUM - A MODEL SYSTEM FOR INTERDISCIPLINARY STUDIES IN ELASMOBRANCH BIOLOGY

The ocular tapetum lucidum has evolved in the elasmobranchs as a means of controlling photon capture by the retina. Tapeta may be of two kinds, fixed and modifiable. In the latter,light reflection from the tapetum is modulated by the movement of screening pigment. In this paper I review past studies of the mechanisms by which such pigment movements are controlled. Evidence is presented that indicates that control is located within the eye itself and is most probably a function of the retina. I also suggest that a complete understanding of ocular tapetum lucidum structure and function awaits the results of studies by workers in various fields of elasmobranch biology, making this subject ideal for an interdisciplinary approach.