Morphological evidence for a probable secretory site of the male sex pheromones of Nauphoeta cinerea (blattaria, blaberidae). 2. electron microscope studies.

Abstract

Light and electron microscopy of the glandular epithelium of intersegmental membranes between sternites three and seven and tergites two and eight of various age groups of Nauphoeta cinerea male adults and one age group of female adults discloses differences in the epithelia of the intersternite and intertergite. The intersternal epithelium appears thicker, more glandular, and stratified. Altogether, seven cell types are recognizable, six in the male and two in the female. They are designated as types 1, 2a, 2b, 2c, 3, 4, and 5. Of these, types 1, 2a, 3, and 4 are recognizable on the sternum; types 1, 2b, and 5 on the tergum of the mature male integuments. Types 1 and 2c are found on the sternum of mature female. The cell types undergo morphological differentiation after adult emergence and show different stages of secretory activity. Type 1 are squamous cuticle-secreting cells; type 2a, 2b, and 2c are columnar-glandular and contain electron-transparent secretory vesicles of various sizes, which increase greatly in number and size in the 5-day-old adult males when the glands are most active. The vesicular size and number also differ between types 2a, 2b, and 2c cells of the same age group. The vesicles are assumed to be derived from smooth endoplasmic reticulum. The type 2 gland cells are also provided with a secretory end apparatus lined by cuticle and bordered by microvilli through which the secretion is believed to be released by exocytosis. The end apparatus leads into a cuticular ductule that opens to the surface of the cuticle as a cup-shaped receptacle, which is more conspicuous in the male intersternite. In the active gland cells, the mitochondria near the end apparatus are swollen and vacuolated. Type 3 cells are seen only on the intersternum and are believed to secrete the cuticular ductule that proceeds from the end apparatus. Type 4 cells are also recognizable only on the male intersternum and contain closely packed, electron-dense bodies, which are most numerous in mature (5-day-old) males. Type 5 cells with their dense cytoplasm are located basally in the intertergal epithelium. The functional significance of type 4 and 5 cells in the males and type 2c cells in the female is not clear. On the basis of differences in morphology, pheromone activity, and sexual behavior, it is suggested that the pheromones secreted by the intersternal and intertergal glands in the male are different, the former secreting a seducin that attracts the female to the male and the latter an "aphrodisiac" acting as a contact pheromone important in accomplishing mating.