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 ofMoina macrocopa-conditioned mediums (MCM) andBrachionus 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 ofM. macrocopaonB. calyciflorus,M. macrocopahad higher sensitivity to the allelochemicals fromB. calyciflorus. When compared to the controls, the chemically-mediated effects ofM. macrocopaon the net reproductive rate (R0), intrinsic rate of population growth (rm) and total number of offspring (NO) ofB. calycifloruswere 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 ofB. calycifloruson theR0,rmand NO ofM. macrocopawere 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) ofB. calyciflorusandM. macrocopacultured in the conditioned medium nearly did not differ significantly from the controls. Our results suggest that the interspecific allelopathic effects ofB. calyciflorusandM. macrocopaare 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.