Structure and alleged functions of avian pineals

Abstract

The pineal is structurally very diverse among the avian species that have been examined. In some birds, especially owls, the pineal is virtually absent. Sympathetic innervation is provided by projections from the superior cervical ganglia. Several cell types are present in the pineal body, among which are large cells, associated with lamellar bodies, that are commonly considered to be abortive or vestigial photoreceptors. Diurnal cycles of serotonin and melatonin content of the pineal are responsive to photoperiod, and there is a small amount of evidence that the avian pineal may serve as a pacemaker for diurnal rhythms of activity. Pinealectomy indicates a role for this body in controlling gonadal function, but the evidence is not consistent. Indole amines may be the mediators of this presumed endocrine role, but the supporting evidence is not very convincing. © 1970 by the American Society of Zoologists.