RESUMEN
The plant genus Ficus is a keystone resource in tropical ecoystems. One of the unique features of figs is the diversity of fruit traits, which in many cases match their various dispersers, the so-called fruit syndromes. The classic example of this is the strong phenotypic differences found between figs with bat and bird dispersers (color, size, presentation, and scent). The 'bird-fig' Ficus colubrinae represents an exception to this trend since it attracts the small frugivorous bat species Ectophylla alba at night, but during the day it attracts bird visitors. Here we investigate day to night changes in fruit scent as a possible mechanism by which this 'bird-fig' could attract bats despite its fruit traits, which should appeal solely to birds. Analyses of odor bouquets from the bat- and bird-dispersal phases (i.e. day and night) differed significantly in their composition of volatiles. We observed a significant increase in relative amounts of sesquiterpene and aromatic compounds at night while relative amounts of two compounds of the fatty acid pathway were significantly higher during day. This finding raises the question whether Ficus colubrinae, a phenotypically classic 'bird-fig', might be able to attract bat dispersers by an olfactory signal at night. Preliminary observations from feeding experiments which indicate that Ectophylla alba is capable of finding ripe figs by scent alone point in this direction. However, additional behavioral experiments on whether bats prefer the 'night-bouquet' over the 'day-bouquet' will be needed to unequivocally answer this question.
Asunto(s)
Conducta Alimentaria/fisiología , Ficus , Odorantes , Dispersión de Semillas/fisiología , Animales , QuirópterosRESUMEN
Abstract: Microplastics can have direct physical effects on organisms in freshwater systems, and are considered as vectors for absorbed environmental pollutants. It is still under discussion if microplastics are relevant pollutant vectors for uptake into aquatic organisms in comparison to further uptake pathways, e.g., via water or sediment particles. We analyzed how the presence of microplastics (polyamide particles, PA) modifies acute effects of the environmental pollutant bisphenol A (BPA) on freshwater zooplankton (Daphnia magna). Daphnids were exposed to PA particles and BPA alone, before combining them in the next step with one concentration of PA and varying concentrations of BPA. The PA particles themselves did not induce negative effects, while the effects of BPA alone followed a typical dose-dependent manner. Sorption of BPA to PA particles prior to exposure led to a reduction of BPA in the aqueous phase. The combination of BPA and PA led to decreased immobilization, although PA particles loaded with BPA were ingested by the daphnids. Calculations based on physiochemistry and equilibrium assumptions indicated lower BPA body burden of daphnids in the presence of PA particles. These results confirm model-based studies, and show that investigated microplastic concentrations are negligible for the overall pollutant uptake of daphnids with water as additional uptake pathway.
Asunto(s)
Compuestos de Bencidrilo/toxicidad , Daphnia/efectos de los fármacos , Nylons/química , Fenoles/toxicidad , Contaminantes Químicos del Agua/toxicidad , Contaminación Química del Agua/prevención & control , Zooplancton/efectos de los fármacos , Adsorción , Animales , Relación Dosis-Respuesta a Droga , Agua Dulce , Pruebas de Toxicidad Aguda , Contaminación Química del Agua/efectos adversosRESUMEN
Currently, there is a trend toward an increasing use of biopesticides assumed to be environmentally friendly, such as Bacillus thuringiensis (Bt). Studies of the Bt toxicity to nontarget organisms have reported low effects at high exposure levels, which is interpreted as indicating negligible risk to nontarget organisms. We investigated the response of the nontarget organism Daphnia magna to waterborne DiPel ES, a globally used Bt formulation. Neonates and adults were exposed for 48 h to a wide range of concentrations, and immobilization and mortality were monitored. Whole body biomarkers (body weight, protein, chitobiase, catalase, xenobiotic metabolism, and acetylcholinesterase) were measured in the adults. The immobilization and mortality of the neonates were affected in a nonmonotonic and inverted U-shaped pattern with EC50s that were â¼105-fold lower than those reported by the manufacturer. The immobilization of adults demonstrated a similar pattern, but significant mortality was not observed. The biomarker results revealed multiphasic dose-response curves, which suggested toxicity mechanisms that affected various physiological pathways. The main particle size in exposure media was in the size range of bacterial spores and crystal toxins. However, the chemical heterogeneity was nonmonotonic, with a change in the phase at the maximum of toxicity (â¼5 µL L-1), which might explain the observed nonmonotonic effects. These results demonstrate the vulnerability of a nontarget organism to a biopesticide that is considered to be safe, while challenging the universal applicability of the central ecotoxicological assumption of monotonicity.
Asunto(s)
Bacillus thuringiensis , Daphnia/efectos de los fármacos , Acetilcolinesterasa/metabolismo , Animales , Catalasa/metabolismo , Desinfectantes/farmacología , Contaminantes Químicos del Agua/toxicidadRESUMEN
Recent studies revealed that freshwaters are not only polluted by chemicals, but also by persistent synthetic material like microplastics (plastic particles <1 mm). Microplastics include a diverse range of characteristics, e.g. polymer type, size or shape, but also their tendency to sorb pollutants or release additives. Although there is rising concern about the pollution of freshwaters by microplastics, knowledge about their potential effects on organisms is limited. For a better understanding of their risks, it is crucial to unravel which characteristics influence their effects on organisms. Analysing effects by the mere particles is the first step before including more complex interactions e.g. with associated chemicals. The aim of this study was to analyse potential physical effects of microplastics on one representative organism for limnic zooplankton (Daphnia magna). We investigated whether microplastics can be ingested and whether their presence causes adverse effects after short-term exposure. Daphnids were exposed for up to 96 h to 1-µm and 100-µm polyethylene particles at concentrations between 12.5 and 400 mg L(-1). Ingestion of 1-µm particles led to immobilisation increasing with dose and time with an EC50 of 57.43 mg L(-1) after 96 h. 100-µm particles that could not be ingested by the daphnids had no observable effects. These results underline that, considering high concentrations, microplastic particles can already induce adverse effects in limnic zooplankton. Although it needs to be clarified if these concentrations can be found in the environment these results are a basis for future impact analysis, especially in combination with associated chemicals.