The cephalic neuroendocrine system of the dragonfly Orthetrum chrysis (Selys) (Anisoptera: Libellulidae)

In O. chrysis 8 groups of neurosecretory cells are present in the brain: 2 medial and 2 lateral groups in the protocerebrum, 2 ventral groups in the tritocerebral lobes and 2 optic groups in the optic lobes. The cerebral neurosecretory cells are classified as AI-, A 2-, B- and C cells. A1 cells are present in the medial groups of the ultimate instar larva and in the adult, while A2 cells are confined to the medial and lateral groups of the larval stage. The B- and C cells occur in all groups of the larval and adult dragonflies. The axons of neurosecretory cells of all the groups form distinct neurosecretory pathways inside the brain. Only a single pair of nerves, the nervi corporis cardiaci, emerges out of the brain and each of them enters the corpus cardiacum on its own side. In the larva as well as in the adult the corpora cardiaca mainly function as storage organs for cerebral neurosecretory material and, secondarily, may also produce their own hormone. The corpora allata are composed of a large number of cells and sometimes they appear as syncytial structures. Cerebral neurosecretory material is never found in the corpora allata or along with any of the nerves of these glands.