Interspecific effects of the cladoceran- (Moina macrocopa) and the rotifer- (Brachionus calyciflorus) conditioned medium on main life history variables in relation to temperature and algal density

Abstract

Current research on the effects of cladoceran allelochemicals on rotifers has been inconclusive and the allelopathic effects of rotifers on cladocerans are unknown. We sought to fill this knowledge gap with life table demography experiments assessing the interspecific effects of Moina macrocopa-conditioned mediums (MCM) and Brachionus calyciflorus-conditioned mediums (CCM) on the main life history variables under different temperatures and algal densities. Our results demonstrate that, when compared to the allelopathic effects of M. macrocopa on B. calyciflorus, M. macrocopa had higher sensitivity to the allelochemicals from B. calyciflorus. When compared to the controls, the chemically-mediated effects of M. macrocopa on the net reproductive rate (R0), intrinsic rate of population growth (rm) and total number of offspring (NO) of B. calyciflorus were non-significant in many cases while in a few the impacts were stimulatory or inhibitory under different concentrations of MCM, temperatures, and food densities. However, when compared to the controls, the allelopathic effects of B. calyciflorus on the R0, rm and NO of M. macrocopa were stimulatory in many cases; some impacts were inhibitory or non-significant under different concentrations of CCM, temperatures, and food densities. In addition, life expectancy at birth (e0), generation time (T), and average lifespan (LS) of B. calyciflorus and M. macrocopa cultured in the conditioned medium nearly did not differ significantly from the controls. Our results suggest that the interspecific allelopathic effects of B. calyciflorus and M. macrocopa are dependent on the origin and concentration of the allelochemical, life history variable, temperature, and food (algal) density. Additionally, the underlying mechanisms should be further investigated.