© 1970 by The Society for Integrative and Comparative Biology
The Epiphyseal Complex in Fish and Reptiles
Department of Biology, Colgate University Hamilton, New York 13346
From a phylogenetic point of view, few organs of vertebrates have shown such a plasticity of form and presumed function as has the epiphyseal complex. From paired, probably sensory, evaginations through the skulls of primitive vertebrates, the single remnant remaining in the higher vertebrates has evolved into a densely cellular, vascular organ with presumably secretory functions. Too few studies are available from throughout the vertebrate series to allow conclusions as to function. Demonstrated effects on reproductive mechanisms, on phototaxis and pigment migration, on behavior, activity, and a variety of other mechanisms are too inconsistent among and between the various groups to permit generalizations other than the likelihood that the epiphyseal complex directly or indirectly is responsive to some manifestation of light or to its absence. Working backward from this assumption, it seems likely that underlying the activity of these complex structures will be a modulation of some basic, homeokinetic mechanism having much to do with the seasonal adjustment of the organism to its environment.