Serotonin and neuropeptide immunoreactivities in the intramolluscan stages of three marine trematode parasites

Abstract

Using an indirect immunofluorescence technique interfaced with confocal scanning laser microscopy, whole-mount preparations of three genera of marine trematode larvae, Cryptocotyle lingua, Cercaria emasculans and Himasthla leptosoma, were screened for 5-hydroxytryptamine (5-HT) and selected neuropeptide immunoreactivities (IRs). IRs for pancreatic polypeptide (PP), peptide YY (PYY) and FMRFamide were found in the central 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 IRs being observed for the different antisera used. PP, PYY and FMRFamide IRs were evident in both central and peripheral components of the nervous 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 rediae of C. lingua, appearing in the form of a network of immunoreactive 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 neuropeptide F (NPF), a native parasitic peptide from the cestode Moniezia expansa. Results demonstrated that serotoninergic and peptidergic components were present in the nervous systems of all of the trematode larvae studied and that some, if not all, of the IR for PP, PYY and FMRFamide was due to the presence of a trematode NPF homologue.

The musculature and associated innervation of adult and intramolluscan stages of Echinostoma caproni (Trematoda) visualised by confocal microscopy

“…Among the trematode larvae previously examined, namely the cercariae of Cryptocotyle lingua, Cercariae emasculans and the echinostome, Himasthla leptosoma, the patterns of 5-HT and FaRP immunostaining were comparable to those in E. caproni throughout both central and peripheral nervous systems (Pan et al 1994). Pan et al (1994) were able to correlate the degree of FaRP expression within developing cercariae when examined within mother rediae with the level of cercarial differentiation, suggesting neuropeptides may be stagespecific messengers in triggering growth and development.…”

“…Pan et al (1994) were able to correlate the degree of FaRP expression within developing cercariae when examined within mother rediae with the level of cercarial differentiation, suggesting neuropeptides may be stagespecific messengers in triggering growth and development.…”

The spatial relationship between the musculature and the 5-HT and FMRFamide immunoreactivities in cercaria, metacercaria and adult Opisthorchis felineus (Digenea)

“…5-HT is generally regarded as the main excitatory neurotransmitter of motor activity in flatworms (see Halton and Maule 2004). The pattern of 5-HT IR neurones in cercariae of O. felineus is similar to those in cercariae of Cryptocotyle lingua, Cercariae emasculans (Pan et al 1994), E. caproni (Šebelová et al 2004) and metacercariae of D. spathaceum and Cotylurus erraticus (Barton et al 1993). The presence of two 5-HT IR neurones in the tail of cercariae has been reported from a. o. Diplostomum chromatophorum (Terenina and Gustafsson 2003b), E. caproni (Šebelová et al 2004) and Echinoparyphium aconiatum (Terenina et al 2006).…”

Is the early left‐right axis like a plant, a kidney, or a neuron? The integration of physiological signals in embryonic asymmetry

“…Such wide conservation of mechanism between the common ancestor of animals and vascular plants requires that protists had access to serotonin-like molecules. Though we do not have access to the protist basal to both plants and animals, we know that protists such as plasmodium and tetrahymena have both serotonin and its receptors (Brizzi and Blum, 1970;Janakidevi et al, 1966;Pan et al, 1994).…”