HISTOLOGY OF THE CORPORA ALLATA OF MELANOPLUS DIFFERENTIALIS (ORTHOPTERA: SALTATORIA)

Abstract

An histological study of the corpora allata of M. differentialis with reference to their functions in control of nymphal development and the production of ripe eggs and o-viducal secretion. 4 classes of cells were recognized: (a) connective tissue and tracheal cells; (b) undifferentiated cells; (c) normal secretory cells; (d) giant secretory or polyploid cells. The undifferentiated cells are small, divide mitotically, and do not contain secretory granules or vacuoles; they show greatest mitotic activity at the beginning of each developmental stage but occasionally divide at other times. The secretory cells, both normal and polyploid, show changes related to secretory function which are fundamentally the same in nymphs and adults and in both sexes. When inactive they are reduced in size and resemble undifferentiated cells; when active they increase in cytoplasmic and nuclear volume, the cytoplasm becomes filled with strongly acidophil granules, and intra-and intercellular vacuoles then appear. At the height of secretory activity of the gland its appearance suggests that materials are flowing from central regions to the periphery. In the 5th nymphal stage, at the end of which only nymphal characters are produced, secretory material is elaborated throughout the intermolt period and is actively released during the latter half of the stage. In the 6th stage, which terminates with the production of adult characters and metamorphosis, the glands are active only during a brief period which begins on the 2d or 3rd day after molting and ends around the middle of the stage. The corpora allata are inactive on the day of the final molt, but elaboration of secretory material begins immediately thereafter. Full secretory activity is achieved shortly before the appearance of oviducal secretion and yolk in adult females, and at an equivalent time in adult males.