Studies on motilityin vitroof an ectoparasitic monogenean,Diclidophora merlangi

Abstract

SummaryAn isometric transducer system has been used to record spontaneous motor activity inDiclidophora merlangi in vitro. Motility took the form of either continuous irregular contractions or bursts of activity with intermittent quiescent periods. Maximal activity was recorded from specimens at 5–8 °C in artificial sea water (ASW). Decerebration induced a period of enhanced motility which subsided within 1 h. Water turbulence elicited large, rapid contractions of the longitudinal body musculature which did not habituate or fatigue. Induced water turbulence at frequencies higher than 3/min inhibited spontaneous movements, resulting in a progressive reduction in contraction amplitude and, eventually (30/min), the abolition of any response to water movement. The neurotoxin tetrodotoxin failed to modify worm activity. Excitatory responses from both intact worms and strip preparations were obtained with 5-hydroxytryptamine, dopamine and noradrenaline, but aminergic antagonists failed to block their effects. Atropine stimulated contractility, whereas the effects of acetylcholine or carbachol were inconsistent. Nicotine increased muscle tone but the effect was unaltered by atropine, mecamylamine ord–tubocurarine. Muscarine, hemicholinium, neostigmine and eserine were without apparent effect.