The Mode of Release of Neurosecretory Material in the Freshwater Pulmonate Lymnaea Stagnalis L. (Gastropoda)

Abstract

Among gastropods, a morphologically established neurosecretory system has been found in the cerebral ganglia of some Basommatcphora and Stylommatophora (Van Mol 1960; Kuhlmann 1963; Röhnisch 1964; Joosse 1964; Nolte 1964, 1965; Simpson et al. 1966a; Lever et al 1965; Cook 1966). There are groups of neurosecretory cells at constant location forming typical neurosecretory tracts by which the secretory products are transported into the neurohemal areas. The various criteria for identification of neurosecretory cells by light- and electron-microscopy are the same as used for vertebrates and higher invertebrates (staining properties, elementary granules, etc.). Cautious interpretation may be necessary, as no definitive functions of neurosecretion have as yet been assigned. Nevertheless, the arrangement of the cells and their processes, the enlargement of the storage space by branching out within the neurohemal areas (Nolte 1965), and the termination in proximity to blood vessels or blood sinuses are strongly indicative of the existence of ‘definite’ neurosecretion in these gastropod species.