Salinity Resistance and Salinity Preference of Two Oligochaetes Aktedrilus monospermatecus Knöllner and Marionina preclitellochaeta N.SP. from the Interstitial Fauna of Marine Sandy Beaches

Abstract

The determination of the salinity of interstitial water by the usual Mohr method is criticized; it is recommended that conductivity measurements be made instead. The work reported on was undertaken on sandy beaches of the Swedish east and west coasts, supplemented by laboratory investigations of two oligochaetes Aktedrilus monospermatecus and Marionina preclitellqchaeta. The latter is being described elsewhere. In the field, Aktedrilus occurred in the sand mainly just above the water line, whereas Marionina was found well above the water line where the salinity of the interstitial water was low. Animals were placed in petri dishes in water of various salinities. Aktedrilus withstood salinities well from 1.3-20%. Marionina survived best in water whose salinity ranged from 2.5-10%;,. An apparatus is described to test salinity preferences of the worms. When offered a choice, Aktedrilus shows a distinct preference to salinities between 2.5 and 5%, whereas Marionina chooses salinities between 0.2 and 0.3%.