Fine structure of pleuropodia in Insecta Orthoptera during embrional development

An ultrastructural examination was carried out on the pleuropodia of three species of Orthoptera Acrididae collected in fourdifferent stages of embryonal development in which the pleuropodia, due to their particular morphology, seem to have a greater activity. From the results obtained it was seen that the pleuropodia of the species examined appear as trilobedestroflexions, made up of a monolayer epithelium, of ectodermic origin, having secretory activity that appeared particularlymarked in correspondence to stage 8 of development during which the embryo extends throughout the egg. Incorrespondence to stage 4, which precedes katatrepsis, the secretory activity mainly consists in the production of electrondense granules; in the other stages of development, instead, other than the granules there were also vesicles having not veryelectron-dense contents, which are liberated among the microvilli. As regards the possible role of the pleuropodia, it has been hypothesized that they are active in the production of enzymes necessary for hatching. The ultrastructural aspect found in correspondence to the poles of the pleuropodial cells, suggests that these formations also have a role in hydro-ionic transport, mechanisms that could, for example, involve an exchange of material between the periembryonal space and thehemocele, without excluding, however, other possible roles inherent in the metabolism of the embryos.