Effect of pH on survival, reproduction, egg viability and growth rate of five closely related rotifer species

In the laboratory we examined the effect of pH (5-10 with one interval) on survival, reproduction, egg viability and growth rate (intrinsic growth rate-r (m) and population growth rate-r) of five Brachionus rotifer species (B. calyciflorus, B. quadridentatus, B. urceolaris, B. patulus and B. angularis). The pH was shown to exert a major influence on egg viability and growth rate (r (m) and r) for each species. The age-specific survivorship curves within a species were not significantly different at pH 6-10. The optimal pH for each species is near-neutral pH (pH 6-8), and the fecundity decreased as the pH deviated from these values. For each Brachionus species, there was no significant difference between age-specific fecundity curves at pH 7 and 8. At acid pH (pH 5 or 6) higher egg mortality was observed for each species. The r (m) and population r of the five Brachionus species incubated at different pHs were significantly influenced by pH. The pH supporting the highest r (m) or r was obtained at pH 6-8, but varied due to species. In this study B. urceolaris and B. patulus could tolerate a broad range of pH, while the populations of B. calyciflorus, B. quadridentatus and B. angulari declined at acid conditions.