Neural Transplants and Insect Diapause

Abstract

THE induction and maintenance of larval and pupal diapause are at present thought to be under the direct control of the neuro-endocrine complex associated with the insect brain. Williams¹ found that diapausing pupæ of the cecropia moth, Hyalophora cecropia, could be induced to resume development by either a prolonged (6–12 weeks) exposure to a low temperature (4–6 ° C) or by the implantation of the brain of a previously chilled pupa. Unchilled diapause pupal brains were found to be incompetent to induce development when implanted into an unchilled pupa in diapause. The competence or incompetence of a pupal brain appeared to depend on the activity or inactivity of its neurosecretory cells. When active, the neurosecretory cells are responsible for the production of a hormone that is released via the corpora cardiaca and activates the prothoracic glands, which then produce the growth hormone, ecdysone, responsible for the initiation of development². In the diapause pupa, the neurosecretory activity of the brain is suppressed³, as is its neural impulse activity⁴.