Observations on the Effects of Changes of Hydrostatic Pressure on the Behaviour of Some Marine Animals

Abstract

An apparatus and experimental method for the investigation of the effects of changes of pressure on the behaviour of marine animals is described.In 43 of a total of 53 species examined in this apparatus definite responses to abrupt pressure changes of 1000 millibars or less have been observed, increased pressure generally causing increased activity and movement upwards or towards the light, and decreased pressure causing decreased activity and movement downwards or away from the light. The relative importance of light and gravity in the orientation of these movements is generally correlated with the degree of development of the light and gravity receptors in the species concerned.The possible significance of these pressure responses in nature is discussed and it is suggested that pressure may be an important factor affecting the distribution of marine plankton, particularly during the hours of darkness.