Neuroendocrine Regulation of the Development of Seasonal Forms of the Asian Comma Butterfly, Polygonia c-aureum L: (neurosecretion/seasonal form/butterfly (Polygonia c-aureum)).

Abstract

In the butterfly, Polygonia c-aureum, development of seasonal forms controlled by the photoperiod and temperature was shown to involve a neuroendocrine system of the brain-corpus cardiacum-corpus allatum complex. For analysis of the neuroendocrine system concerned, the innervation of the complex was investigated first by cobalt chloride perfusion staining and then by severance of axons, ablation of the candidate cells, injection of a homogenate of these cells and transplantation of corpora cardiaca using pupae programmed to be either summer-form or autumn-form adults. The results suggested that medial nerve cells produce what is called material producing the summer form. The seasonal forms of the Asian comma butterfly, Polygonia c-aureum L., summer and autumn forms (Fig. la, b), are determined by the photoperiod and the temperature during the larval period (1-3). Previous studies have given the following results on the physiological mechanism involved in the effect of environmental factors in inducing these seasonal forms. First, the mechanism involves neurosecretory cells located somewhere in the brain (2). Second, the nervous connections between the brain and the corpus cardiacum (NCC I+II (4)) and between the right and left brain lobes are indispensable for the effect (2, 5-7). The present study consisted of two series of experiments. One was designed to demonstrate morphologically the axonal connection of the corpus cardiacum with the corpus allatum in this butterfly, like that shown in several other insects (8-13). The other series was designed to locate the neurosecretory cells producing material related to the seasonal form and to see if this material is also present in the corpus cardiacum.