The pineal body and pinealectomy in the cotton rat, Sigmodon hispidus

The pineal body is known to be an important component in the regulation of seasonal reproduction. The gross morphology of the rodent pineal gland is highly variable and this variability may be related to the degree of its involvement in regulating reproduction. The size and complexity of the pineal gland of the cotton rat appear to be well correlated with the known reproductive responses of this species to photoperiod. The cotton rat pineal is a large (2,500 micrometer X 500 micrometer) mass originating from the dorsal diencephalon and extending dorsally to the superior sagittal sinus. The cotton rat pineal is solid and cannot be divided into deep and superficial portions as in some rodents. Animals obtained from the field were found to survive conventional pinealectomy when it was carried out under methoxyflurane anesthesia. These results indicate that the cotton rat could be used as a wild animal model for pineal gland-seasonal reproduction research.