Untersuchung über den Wasserwechsel der Seeigel und seine Bedeutung für Atmung und Exkretion

Abstract

Measurements of the quantities of sea water taken in by the mouth and expelled by the anus show that Echinus esculentus L. drinks water at more or less regular intervals. The amounts of water taken in through the mouth increase allometrically in relation to body volume. Upon stimulation, drinking rate may rise to more than ten times the basic rate. Since the amount of water leaving the body through the anus exceeds that entering through the mouth, additional water must be absorbed through the body surface and excreted by the gut. The amount of water influx via body surface is especially high in smaller individuals. Drinking, influx and excretion of water are discussed with regard to respiration and excretion: hasty drinking, caused by stimulation, can increase the supply of oxygen to the perivisceral cavity, and subsequent excretion supports the removal of metabolic wastes. The following mechanism of water influx is proposed and discussed: As a consequence of excess K+ and Ca++ ions in the ambulacral system, due to an ion pump, there exists a small inward directed osmotic gradient causing water to enter the lumina of the expanded tube feet. When the tube feet contract, most of the absorbed water is forced through the ampulla walls into the perivisceral cavity, from where it is actively excreted by the gut, together with metabolic wastes. © 1972 Biologischen Anstalt Helgoland.