Neurosecretion and the endocrinology of nereid polychaetes

Abstract

The endocrine activity of the nereid brain supports caudal regeneration in young worms and inhibits both the onset and progress of gametogenesis and metamorphosis. A single hormone is believed to influence these processes. There is also evidence that the nereid brain, like that of many other polychaetes, secretes a tropic hormone that is indispensable for normal vitellogenesis. It is not known if the inhibitory and tropic functions of the brain are caused by separate hormones. The cellular origin of this endocrine activity is unknown. Some cerebral neurosecretory cells have terminals located in the infracerebral complex on the ventral region of the brain. The infracerebral complex, which has some features of a neuroendocrine organ, also has epithelioid infracerebral cells, one type of which resembles cerebral neurosecretory cells. The infracerebral complex is undoubtedly hormonogenic but the functions and interactions of its various components are unknown. Evidence that cerebral neurosecretory cells of nereids produce neurohormones or control the activity of infracerebral cells is circumstantial. The neuroendocrine status of this neurosecretory system is uncertain in the absence of demonstrated interactions between nervous and non-nervous endocrine tissues. © 1976 by the American Society of Zoologists.