Activity and respiration in the anemone, Metridium senile (L.) exposed to salinity fluctuations

Activity and respiration in the anemone, Metridium senile (L.), were monitored under both constant and fluctuating salinity conditions. During constant exposure to 50% sea water it was found that the animals retracted the tentacles and that the rate of oxygen consumption decreased by ≈50%. The same response was elicited from animals in 100% sea water in a contracted state. Animals exposed to continually fluctuating salinities were found to retract the tentacles, contract the body wall, and produce amounts of mucus during periods of decreasing salinities. These reactions were reversed during exposure to increasing salinity. Oxygen consumption never ceased entirely in animals exposed to dilute sea water and it was found that during declining oxygen tension M. senile regulated its oxygen consumption until the environmental oxygen tension fell to ≈30% saturation.