Rotifer Growth Rate Research Articles

Bacterial additives that consistently enhance rotifer growth under synxenic culture conditions: 1. Evaluation of commercial products and pure isolates

Axenic rotifers ( Brachionus plicatilis Müller) were cultured under aseptic conditions; they were fed either a bacteria-free artificial diet (AD), or axenic Isochrysis galbana, or a combination of axenic Chlorella minutissima and the bacteria-free AD. The medium was inoculated with commercial bacterial additives or cultured strains of marine bacteria. The highest improvements in growth rate (GR) of rotifer populations were obtained with laboratory grown bacteria. Addition of an Alteromonas strain and an unidentified Gram negative strain (B3) consistently enhanced rotifer GR in all experiments, and under all feeding regimes in comparison with control cultures inoculated with microbial communities present in seawater, or maintained bacteria-free. None of the other isolates or commercial products were consistent in their enhancement of rotifer production.

Selection of bacteria enhancing the growth rate of axenically hatched rotifers ( Brachionus plicatilis)

The effect of bacterial strains on the growth rate of rotifers, Brachionus plicatilis, was determined under monoxenic conditions. The first objective was to obtain sterile rotifer cultures starting from rotifer resting eggs using merthiolate or glutaraldehyde as disinfectant. Sterile rotifer cultures were obtained, without affecting the hatching ability of the resting eggs, when 0.05 μl/l glutaraldehyde was used. This disinfection procedure was used to examine the effect of 20 bacterial strains, isolated from well-performing live-feed production systems, on the population growth rate of rotifers cultured under monoxenic conditions. Five out of the 20 bacterial strains tested were able to improve significantly the asexual reproduction of rotifers. The population growth rate ( μ pop) of rotifer cultures treated with GR 12 and GR11 (respectively 0.664±0.043 and 0.622±0.062) was significantly higher than the μ pop of the control treatment (0.512±0.101). Overall, the egg ratio after 48 h was significantly higher in the cultures inoculated with the bacterial strains than in the axenic control treatment. The results show that it is possible to control the microbial community in rotifer cultures started from disinfected resting eggs by adding bacterial strains which have a positive effect on the population growth rate.

Use of a potential probiotic Lactococcus lactis AR21 strain for the enhancement of growth in the rotiferBrachionus plicatilis(Müller)

The effect of a potential probiotic on the growth performance of a rotifer and its inhibition against Vibrio anguillarum was studied. Probiotic strain AR21 had no significant observable effect on the growth rate of rotifers under optimal culture conditions in three consecutive experiments. In the first and second experiments, the AR21 strain exhibited an inhibitory effect against the V. anguillarum strain when rotifer cultures were maintained at a suboptimal feeding regime. The growth rate of the rotifers in suboptimal feeding conditions was significantly higher in the treatment receiving AR21 and V. anguillarum than in the treatment where only V. anguillarum was added.

The importance of Daphnia in determining mortality rates of protozoans and rotifers in lakes

We measured mortality of protozoans and rotifers in three lakes of contrasting zooplankton communities. We also compared protozoan growth in an experiment which controlled Daphnia biomass but varied body size. Mortality was determined as the difference between growth rates over 24 h in containers with and without zooplankton. Growth rates of heterotrophic flagellates and ciliates were high in the presence of a small assemblage of zooplankton and near zero or negative when either Daphnia pulex or Daphnia galeata was the dominant zooplankton species. Growth rates of rotifers were also usually lower in the presence of Daphnia. Mortality rates of heterotrophic flagellates, ciliates, and rotifers were positively related to the mean body size of Daphnia in comparisons among experiments. In an experiment with equal biomasses but different sizes of D. pulex, flagellate growth rates were lower in treatments with large Daphnia. High mortality in zooplankton communities dominated by larger species of Daphnia appears to be important in determining differences in the abundances of protozoans and rotifers among lakes.

Effect of growth rate on the physiological rates of a chemostat-grown rotifer Encentrum linnhei

The physiological rates of a normally omnivorous marine rotifer, Encentrum linnhei, were measured under the steady-state chemostat conditions in which the physiological state of the food-algae was kept constant whilst the rotifer growth rate was changed to preset levels. The specific clearance rate ranged between 50 and 100 μl/μg rotifer C/day (1.5–3.0 μ/rot/day) and varied hyperbolically with growth rate, a similar curve was obtained with the specific ingestion rate which varied between 1–2 μg C/μg rot C/day. A mean respiration rate of 0.45 μg C/μg rot C/day was obtained from oxygen consumption measurements. About 60‰ of ingested energy was found to be egested as paniculate matter and 9–4 °0 dissipated as heat, the latter comparing with a theoretical figure of 4–5‰.From rates, transfer efficiencies were obtained giving a mean net growth efficiency (K2) of 38‰ and a mean overall growth efficiency (K1 of 15‰. A curvilinear increase of Kl with growth rate contrasts with linear and hyperbolic responses found with brachionid rotifers.