The osmoregulatory function of the vibratile flames and the contractile vesicle of Asplanchna (Rotifera)

Abstract

1.The experimental results provide strong evidence that the vibratile flames and contractile vesicle of Asplanchna are components of an osmoregulatory system.2.In fresh water and at constant temperature, the rate of beat of the vibratile flames of Asplanchns and the rate of output of fluid from the contractile vesicle vary from one species to another.3.An increase in the ionic concentration of the external medium results in a decrease in the rat of beat of the vibratile flames, and this effect is reversible.4.An increase in the ionic concentration of the external medium results in a decrease in the rate of output from the contractile vesicle, and this effect is reversible.5.An increase in temperature results in an increase in the rate of beat of the vibratile flames and in the rate of output from the contractile vesicle.6.The increase in rate of beat of the flames in response to increased temperatures above 22°C id greater than that to increased temperatures below 22°C.7.Correlation of flame and vesicle activity suggests that there is an optimum size for the flame bulbs.8.The vibratile flames of Asplanchna show an activity in inverse relationship to the concentration of the medium, and not an “all or none” effect.9.The medium with which the body fluid of Asplanchna is estimated to be isosmotic is 100–160 mOsm sodium chloride/1 for A. priodonta and 130–175 mOsm sodium chloride/1 for A. brightwelli.10.The estimated internal concentration of Asplanchna is comparatively high. It is suggested that this is concentrated with the maintenance of turgor in the animal.11.The turgor pressure of the body fluid of Asplanchna pridonta is suggested as being of the order of 40 mOsm sodium chloride/1.