SEROTONIN AND NEUROPEPTIDE IMMUNOREACTIVITIES IN THE INTRAMOLLUSCAN STAGES OF 3 MARINE TREMATODE PARASITES

Using an indirect immunofluorescence technique interfaced with confoca l scanning laser microscopy, whole-mount preparations of three genera of marine trematode larvae, Cryntocotyle lingua, Cercaria emasculans a nd Himasthla leptosoma, were screened for 5-hydroxytryptamine (5-HT) a nd selected neuropeptide immunoreactivities (IRs). IRs for pancreatic polypeptide (PP), peptide YY (PYY) and FMRFamide were found in the cen tral nervous systems of the three species of cercariae, immunostaining the paired ganglia and central commissure and the longitudinal nerve cords, with slight differences in both distribution and intensity of I Rs being observed for the different antisera used. PP, PYY and FMRFami de IRs were evident in both central and peripheral components of the n ervous system in the rediae of C. lingua. 5-HT IR was confined to the peripheral nervous systems of the cercariae of C. emasculans and the r ediae of C. lingua, appearing in the form of a network of immunoreacti ve fibres and associated large cell bodies. A moderate substance P IR was observed in the nervous system of the cercariae of C. lingua. The patterns of immunostaining described were compared with those obtained using antiserum directed to the C-terminal decapeptide amide of neuro peptide F (NPF), a native parasitic peptide from the cestode Moniezia expansa. Results demonstrated that serotoninergic and peptidergic comp onents were present in the nervous systems of all of the trematode lar vae studied and that some, if not all, of the IR for PP. PYY and FMRFa mide was due to the presence of a trematode NPF homologue.