The neuro-muscular system in cercaria with different patterns of locomotion

The neuro-muscular system (NMS) of cercariae with different swimming patterns was studied with immunocytochemical methods and confocal scanning laser microscopy. Specimens of the continuously swimming Cercaria parvicaudata, Maritrema subdolum and Himasthla elongata were compared with specimens of the intermittently swimming Cryptocotyle lingua and the attached Podocotyle atomon. The patterns of F-actin in the musculature, 5-HT immunoreactive (-IR), FMRFamide-IR neuronal elements, α-tubulin-IR elements in the nervous and sensory systems and DAPI-stained nuclei were investigated. The general plan of the NMS was similar in all cercariae studied. No major structural differences in the patterns of muscle fibres were observed. However, in the tail of C. lingua, transverse muscle fibres connecting the bands of longitudinal muscles were found. No major structural differences in the 5-HT- or FMRFamide-IR nervous systems were observed. The number of 5-HT-IR neurones in the cercarial bodies varied between 12 and 14. The number and distribution of the α-tubulin-IR processes on the cercarial bodies and tails differed from each other. The relation between the number and structure of the α-tubulin-IR processes and the host finding strategy of the cercariae is discussed. A detailed schematic picture of the NMS in the tails of C. lingua and M. subdolum is presented.