Relationship between the Temperature Given at the Time of Fertilized Egg Formation and Bisexual Reproduction Pattern in the Deriving Strain of the Rotifer Brachionus plicatilis

Abstract

Temperature given at the time of fertilized (resting) egg formation in the rotifer Brachionus plicatilis was discussed, from a point of view that it may cause great difference in bisexual repro-ductivity among the deriving strains. Fertilized eggs were produced at five temperatures (17, 20, 25, 27 and 30°C) in sea water. Neonates from the eggs were employed as stem mothers of respective experimental strains. Every strain consisted of isogenic individuals through keeping parthenogenesis, which was ensured by the individual culture in 0.1 ml seawater medium. Media were renewed at regular intervals of 12, 24 or 36 hours at 30, 25 or 20°C respectively in order to prevent the accumulation of metabolites which is an exciting cause of bisexual reproduction. The temperature given in the process of fertilized egg formation determines the bisexual reproduction pattern of deriving strains. Among the strains derived from the fertilized eggs which were produced at high temperature over 25°C, the appearance rate of mictic females has no relation to temperature. Among those, however, derived from the eggs originating in low temperature below 25°C, it varies inversely with temperature below 25°C, but not affected above 25°C. © 1985, The Japanese Society of Fisheries Science. All rights reserved.