HISTOPHYSIOLOGICAL STUDIES ON THE CORPUS ALLATUM OF LEUCOPHAEA MADERAE. I. NORMAL LIFE CYCLE IN MALE AND FEMALE ADULTS

Abstract

The corpora allata of the insect Leucophaea maderae display a remarkable degree of structural variability in conjunction with changing functional states. This is particularly apparent in adult females, where a regular sequence of activity and inactivity of these glands parallels alternating phases of ovarian development and quiescence. The volumetric rise signalling activation of the corpora allata is accomplished to a large extent by an absolute and relative increase in cytoplasmic content which results in a characteristic "loose" distribution of the nuclei. During each growth period of these glands the nuclear numbers increase up to several times the original values. When, after ovulation, the corpora allata return to a state of inactivity which is maintained during pregnancy, the nuclear-cytoplasmic ratio returns to a level characteristic of the newly emerged female. The accompanying reduction in cell number to the initial level is evident not only from a drop in nuclear counts but from the observation of pyknotic nuclei. The differences in the frequencies with which nuclear pyknosis on one hand, and mitotic figures on the other are observed in various stages suggest the existence of a cellular turnover which seems continuous but whose rate changes periodically. During activation of the corpus allatum the increase in cell number surpasses the rate of cell destruction; in the regressing gland the latter process predominates over that of cell replacement. Distinct secretory granules have been demonstrated in the corpus allatum of Leucophaea. These granules line up along cell processes which are directed to the surface of the corpus allatum. The active substance seems to be released into the surrounding hemolymph. By comparison with the situation in females, the corpora allata of adult males show considerably less variability. Since the available information on the functional role of the corpora allata in male adult animals suggests no pattern of periodicity, the lack of distinct cyclic changes in the morphology of these glands is not surprising.