part of start stage end stage central pretectum ventral accessory optic nucleus TAO:0000454 ZFA:0000454 zebrafish_anatomy Diencephalic nucleus that is part of the central pretectum and is ventromedial to the magnocellular superficial pretectal nucleus and the caudal pretectal nucleus. The ventral accessory optic nucleus is very large in zebrafish as compared to other cyprinids. From Neuroanatomy of the Zebrafish Brain. diencephalic nucleus unknown adult