NEUROSECRETORY-CELLS IN THE POSTERIOR CECA OF THE AMPHIPODS ORCHESTIAAND NIPHARGUS - ULTRASTRUCTURAL CHARACTERIZATION

The epithelium of the midgut posterior caeca of the amphipods Orchesti a cavimana and Niphargus virei includes, besides previously studied ma in cells, basal cells which have been structurally evidenced as neuros ecretory cells, and comparatively described employing electron microsc opical techniques. The functional involvement of this new cell-compone nt in the physiology of the caecal epithelium is then comparatively di scussed, as both epithelia are involved in analogous transporting acti vities during the molt cycle, but their cellular equipment is differen t. In Orchestia, where paracrine cells, a third cell-component of the caecal epithelium, have been previously observed, the neurosecretory a ctivity of basal cells is lower than in Niphargus which does not inclu de any paracrine cells. Thus, it is proposed that paracrine cells of O rchestia may have functions partly equivalent to those of basal cells of Niphargus in the regulatory processes of the physiology of the caec al epithelium.