Demography of the sessile rotifers, Limnias ceratophylli and Limnias melicerta (Rotifera: Gnesiotrocha), in relation to food (Chlorella vulgaris Beijerinck, 1890) density

Abstract

We developed a simple method to culture two sessile rotifers, Limnias ceratophylli and Limnias melicerta, which should be applicable to other sessile species, and examined effect of the concentration of Chlorella vulgaris on population growth of these species. Limnias ceratophylli had higher population abundances at higher food levels. For both species, intrinsic rate of increase (r), derived from population growth study, varied from 0.12 to 0.16 day−1. Differences in r varied depending on food level for L. ceratophylli, but not for L. melicerta. Both species had little mortality during 2–3 weeks and thereafter survivorship declined until 5–7 weeks depending on food concentration. Mean life expectancy at birth for L. ceratophylli and L. melicerta was 29–34 days and 28–33 days, respectively. Generation time was shorter for L. ceratophylli. Gross and net reproductive rates were higher for L. ceratophylli. For both species, increase in food density resulted in significant decrease of average lifespan and life expectancy at birth. Gross reproductive rate and rate of population increase of both species were not significantly affected by food density. Generation time was significantly affected due to increase in algal food only for L. ceratophylli but not for L. melicerta.