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

¹ Department of Anatomy, Albert Einstein College of Medicine, New York 61, New York

1. The corpora allata of 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.

2. The volume of active corpora allata surpasses that of inactive glands beyond the range of individual variation, which is considerable. The volumetric rise signalling activation 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.

3. The present study shows further that the nuclei participate significantly in the cyclic changes of these organs. During each growth period, the nuclear numbers increase up to several times the original values. When, after ovulation, the corpus allatum returns 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 pycnotic nuclei.

4. The differences in the frequencies with which nuclear pycnosis 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, when secretory products are elaborated, the increase in cell number surpasses the rate of cell destruction. In the regressing gland the latter process predominates over that of cell replacement.

5. With the use of a modified aldehyde fuchsin technique distinct secretory granules have been demonstrated in the corpus allatum cells of Leucophaea. The granules line up along processes of the cells which are directed to the surface of the corpus allatum. This fact, as well as the accumulation of stainable granules in the periphery of the gland, speaks for the release of the active substance into the surrounding hemolymph. The occurrence of pycnotic nuclei in cells filled with secretion granules suggests that these gland cells may become exhausted fairly quickly, perhaps in the course of one secretory cycle.

6. By comparison with the situation in the females, the corpora allata of adult males show considerably less variability. Soon after emergence, a short period of "activation" seems to occur, as judged by the same structural characteristics as in the females. After that a fairly constant level of presumably mild activity appears to be maintained throughout adult life. 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.