Anatomical identification of the neuroendocrine system in the Nothobranchius furzeri brain

The hypophysis functions as a central gland of the neuroendocrine system for regulating fundamental body physiology. Upon aging, several hormones produced by the endocrine system are dramatically altered. Recently, Nothobranchius furzeri (the turquoise killifish) has become a popular model for aging studies because of its short lifespan and highly conserved aging phenotypes. However, the anatomical details of the major neuroendocrine system of the killifish have not been investigated so far. In this study, we have identified the pituitary and pineal glands of the turquoise killifish, which are critical components of the brain endocrine system. These two neuroendocrine glands were weakly attached to the main body of the killifish brain. The pineal gland was located on the dorsal part of the brain, while the pituitary gland was located on the ventral part. Brain sections containing pineal and pituitary glands were performed and revealed that cells in both the pituitary and pineal glands are densely placed than any other regions of brain. Further, three-dimensional images both in pineal and pituitary glands were uncovered their distinctive cellular arrangements. Vasopressin intestinal peptide (VIP) was strongly expressed in the neurohypophysis of the pituitary gland. Glial cells were found inside the pineal gland, while astrocytes covered the outside. These findings illustrate basic features of the neuroendocrine system of Nothobranchius furzeri.