LOCALIZATION, QUANTITATION, AND CHARACTERIZATION OF NEUROPEPTIDE-F-IMMUNOREACTIVE AND FMRFAMIDE-IMMUNOREACTIVE PEPTIDES IN TURBELLARIANS AND A MONOGENEAN - A COMPARATIVE-STUDY

Over the past decade it has become clear that the nervous systems of p latyhelminths are both complex and highly developed, particularly in p eptidergic elements. The central position of an ancestral flatworm in the evolution of the Bilateria has placed a greater importance on the study of modern flatworms. Using antisera generated to the C-terminal region of platyhelminth neuropeptide F and the molluscan neuropeptide, FMRFamide, in immunocytochemistry at both Light and ultrastructural l evels, immunoreactivities have been localised within the nervous syste ms of three species of triclad turbellarians, Dugesia lugubris, Dendro coelum lacteum, and Polycelis nigra, and one species of monogenean tre matode, Diclidophora merlangi. Extensive immunostaining was obtained w ith both antisera throughout the central and peripheral nervous system s of all species studied, but intensity and abundance was significantl y greater in the turbellarians. Indirect electron-immunogold labeling demonstrated that immunoreactivity to both neuropeptides was often col ocalised in neurosecretory vesicles, although discrete populations of vesicles were also observed. Radioimmunoassay of extracts of all speci es confirmed that neuropeptide F immunoreactivity was consistently mor e abundant than FMRFamide immunoreactivity, and that the levels of bot h in the three turbellarians were several orders of magnitude greater than those found in the monogenean. Chromatographic analyses of turbel larian extracts revealed that neuropeptide F and FMRFamide immunoreact ivities were attributable to different peptides. These data imply that the neuropeptidergic systems of turbellarians are considerably more e xtensive than those of monogeneans, and would suggest that a regressio n has occurred in the latter as a consequence of the adoption of a mor e sedentary parasitic lifestyle. (C) 1995 Wiley-Liss, Inc.