In the nervous system of the obligatory endoparasite Diphyllobothrium dendriticum immunoreactivity (IR) to growth hormone-releasing factor (GRF), peptide histidine isoleucine (PHI), bovine pancreatic polypeptide (BPP), gastrin, gastrin-releasing peptide (GRP), oxytocin, FMRFamide (FMRF) and serotonin (5HT) was demonstrated by immunocytochemical methods. A very strong GRF-IR was observed in the CNS and PNS of larvae and of the constantly growing adult worms. GRF-IR axon terminals occur beneath the basal lamina of the tegument along the inside of the bothridia, the holdfast organ of the worm. GRF-IR fibres surround the yolk producing vitelline glands and occur in the wall of the vagina. PHI-IR was observed in the CNS and PNS of larvae and adult worms. PHI-IR terminals occur beneath the basal lamina of the tegument along the strobila, the nutrient absorbing surface of the worm. PHI-IR fibres seem to innervate the testicular follicles. FMRF-IR fibres and perikarya occur close to the vitelline glands and the uterine pore and in the male copulatory organ. Numerous large 5HT-IR perikarya with long varicose fibres were observed in the nervous system of the worm. 5HT-IR perikarya occur close to the genital atrium. D. dendriticum is the phylogenetically lowest organism in which IR to PHI has been demonstrated.

No abstract

Immunoreactions (IR) in the nervous systems (NS) of species representing the platyhelminthic taxa Acoela, Proseriata, Tricladida and Rhabdocoela (Dalyellioida, Typhloplanoida, Kalyptorynchia) have been studied by means of the peroxidase‐antiperoxidase (PAP) immunocytochemical method and the whole mount immunofluorescence (FITC) method. Antisera to the molluscan cardioactive neuropeptide FMRF‐amide, to the bioamine 5‐HT and to the vertebrate neuropeptides bovine pancreatic peptide (BPP), leu‐enkephalin, substance P and human growth hormone releasing factor (GRF) were used. Perikarya and fibres positive to FMRF‐amide antiserum (anti‐FMRF‐amide) appear in the NS of all investigated species. Since IR to anti‐FMRF‐amide has been obtained in worms representing taxa of all flatworm classes it is suggested that substances with similar sequences have been inherited from the stem form of Platyhelminthes. IR to 5‐HT antiserum (anti‐5‐HT) observed in the NS of all the investigated flatworms confirm the importance of this bioamine, which may have appeared early in platyhelminth evolution. IR to GRF antiserum was found in the acoel, the triclad and the rhabdocoel species, IR to leu‐enkephalin antiserum in the triclad and rhabdocoel species and IR to substance P antiserum in the rhabdocoels.