INCREASED SEXUAL REPRODUCTION IN BRACHIONUS-PLICATILIS (ROTIFERA) WITH THE ADDITION OF BACTERIA AND ROTIFER EXTRACTS

Previous works revealed that sexual reproduction of brachionid rotifers increases with increasing population density. It is also known that the renewal of environmental water suppresses sexual reproduction in Brachionus plicatilis O.F. Muller populations. The cause of these actions, however, remains unknown. In this study, we investigated the effects of bacterial additions to axenic rotifer B. plicatilis cultures as well as the the effect of rotifer extracts on sexual and asexual reproduction. Out of 17 bacterial strains tested, rotifer sexual reproducion (mixis) rates were 4-10 times higher than controls with addition of three Pseudomonas strains, a Moraxella strain and a Micrococcus strain. Rotifer mixis rate also increased with the addition of a water soluble extract from 1000 rotifers to 5 ml axenic rotifer cultures. Similar results were obtained for resting egg formation.