Neuropeptides in free-living and parasitic flatworms (Platyhelminthes). An immunocytochemical study

Abstract

The nervous systems of the turbellarians Microstomum lineare and Polycelis nigra and of the cestodes Diphyllobothrium dendriticum and Schistocephalus solidus were studied by means of the peroxidaseantiperoxidase (PAP) immunocytochemical method, with the use of antisera to the neuropeptides FMRFamide, vasotocin, leu-enkephalin, met-enkephalin, neurotensin, somatostatin, and VIP, and to the bioamine serotonin. Anti-FMRF-amide positive perikarya and fibers occurred in all species, while the occurrence of the vertebrate brain-gut peptides and serotonin varied between the species . Anti-somatostatin and anti-VIP gave a negative result . Anti-FMRF-amide and anti-vasotocin positive immunoreactivity was found in the brain and gut of M. lineare, and in the CNS and the peripheral nerve net of the cestodes . We suggest that the brain-gut peptides of free-living flatworms act on the subtegumental region in the cestodes, which lack a gut but absorb their nutrients directly through the tegument .

Immunocytochemical Evidence of Neuroactive Substances in Flatworms of Different Taxa—a Comparison

“…IR to these substances is obtained in all investigated species. Previous studies have revealed anti-FMRF-amide IR in the following flatworm taxa: Catenulida (Wikgren and Reuter 1985), Macrostomida (Reuter et al 1984, 1986, Tricladida (Wikgren et al 1986), Monogenea (Reuter 1987), Digenea (Gustafsson 1987) and Cestoda (Gustafsson et al 1985). The additional findings of FMRF-amide-like IR in the Rhabdocoela, the Proseriata and the Acoela and its occurrence in Coelenterata (Grimmelikhuijzen 1984) support the status of this peptide family as symplesiomorphic in the Platyhelminthes (Wikgren and Reuter 1985) and the substances as ancestral, evolutionarily relatively stable, neuroregulating substances of crucial importance in primitive nervous systems (Grimmelikhuijzen 1983).…”

“…In addition, IR to bovine pancreatic polypeptide (BPP) and to vasotocin antisera has been reported for this flatworm (Wikgren et al 1986, Reuter andPalmberg 1987). In planarians IR has been demonstrated to FMRF-amide, 5-HT, leu-enkephalin, met-enkephahn, neurotensin, somatostatin, ACTH and neurophysin antisera (Schilt et al 1981, Carraway et al 1982, Kerschbaum et al 1984, Wikgren et al 1986). In the monogenean species Gyrodactylus salaris IR has been obtained to anti-5-HT, anti-FMRF-amide, anti-GRF, anti-leu-enkephalin and anti-urotensin I (Reuter 1987).…”

“…In the macrostomid Microstomum lineare, too, FMRF-amide and 5-HT antisera reveal positive fibres and perikarya (Reuter et al 1984(Reuter et al , 1986. In addition, IR to bovine pancreatic polypeptide (BPP) and to vasotocin antisera has been reported for this flatworm (Wikgren et al 1986, Reuter andPalmberg 1987). In planarians IR has been demonstrated to FMRF-amide, 5-HT, leu-enkephalin, met-enkephahn, neurotensin, somatostatin, ACTH and neurophysin antisera (Schilt et al 1981, Carraway et al 1982, Kerschbaum et al 1984, Wikgren et al 1986).…”

“…In the last five years a number of immunocytochemical (ICC) investigations demonstrating biologically active peptides (BAP) in the central and peripheral nervous system (CNS and PNS) of platyhelminths have been published. Immunoreactivity (IR) to the molluscan cardioactive neuropeptide FMRF-amide, to the biogenic amide 5-HT and to nine different vertebrate BAP antisera has been demonstrated in the cestode Diphyllobothrium dendriticum (Gustafsson et al 1985(Gustafsson et al , 1986. In the catenulid Stenostomum leucops positive reactions to FMRF-amide and 5-HT antisera and to three vertebrate neuropeptide antisera, anti-P-endorphin, anti-GRF and anti-substance P, have been reported (Wikgren and Reuter 1985).…”

“…In the catenulid Stenostomum leucops positive reactions to FMRF-amide and 5-HT antisera and to three vertebrate neuropeptide antisera, anti-P-endorphin, anti-GRF and anti-substance P, have been reported (Wikgren and Reuter 1985). In the macrostomid Microstomum lineare, too, FMRF-amide and 5-HT antisera reveal positive fibres and perikarya (Reuter et al 1984(Reuter et al , 1986. In addition, IR to bovine pancreatic polypeptide (BPP) and to vasotocin antisera has been reported for this flatworm (Wikgren et al 1986, Reuter andPalmberg 1987).…”