Publicação
Responses of Daphnia magna and Daphnia similis exposed to chemicals during various generations
| Resumo: | Anthropogenic pressure negatively affects natural environments through the introduction of various types of stressors, from chemical, physical or biotic. Different species may present different sensitivities to such stressors, therefore, this research evaluated the sensitivity of two monophyletic species of daphnids, the tropical Daphnia similis and the model temperate species Daphnia magna to a lead (Pb) exposure, as well as combined with the fungicide mancozeb. Moreover, since aquatic organisms may be exposed for long periods, or pulse exposures, the experimental design used was based on a multi-generation exposure to evaluate offspring sensitivity/fitness, sensitivity and possible recovery through generations. The main goals of this study were: 1) Compare the toxicity of chemical compounds to two daphnid species, representing different climate regimes 2) Compare the effects of Pb between species in a long-term exposure, for more realistic responses 3) Estimate if Pb exposure would affect the sensitivity to other chemicals (e.g. pulse exposure), 4) Evaluate if food quantity affect organisms’ sensitivity to long-term exposures and, 5) Assess organisms’ recovery after a generational Pb exposure. In this context, D. magna presented a lower Pb sensitivity than D. similis, and mancozeb triggered opposite outcomes for the two species tested. The nine generation Pb exposure indicated a diminished Pb sensitivity for both species. A lower mancozeb sensitivity for Pb exposed organisms occurred for D. magna, while D. similis showed an opposite response. The generational assay indicated an enhanced rate of population increase (r) for both species, however, enhanced feeding rate occurred only for D. similis. Other contrasting effects among species caused by a long-term Pb exposure was seen for the Net Reproductive Rate (R0) which was not affected for D. magna and was diminished for D. similis. Meanwhile, early reproduction, reduced lifespan and AChE activity were shown for D. magna but not for D. similis. No disparity was shown between species considering adverse Pb effects. Generational Pb exposure led to carapace malformations, possible Pb granules in neonates’ dorsal region, reddish extremities in neonates (possibly indicating increased haemoglobin content). Considering reproduction, negative effects occurred such as male production, ephippias (or dormant haploid egg), eggs color variation (green and white) and abortion. Pb accumulation in D. magna through generations presented a faster and saturated Pb accumulation under usual food and a gradual concentration increase under food restriction, with a successful recovery (both food regimes). Pb exposure presented a general pattern of D. magna failed retrieval (may be due to ephigenetics) and D. similis successful retrieval (phenotypic acclimation) to levels similar to control (successful) organisms. The effect of Pb on reproduction, respiration, induction of malformation, and other adverse effects suggests that a chronic generational exposure can be harmful to both Daphnia species. The most important highlights of this study were; 1) Daphnia magna and Daphnia similis are capable of diminishing Pb sensitivity across a long-term Pb exposure, 2) Pb pre-exposure can affect daphnids’ sensitivity to other chemicals, 3) Pb exposure may increase the population of acclimated organisms in natural habitats, 4) Both species differ regarding recovery (epigenetics or physiological acclimation), 5) Different responses occur in single and generational exposures from monophyletic species (especially under oligotrophic media, typical of natural habitats). These results indicate the importance of accomplishing ecotoxicological assays with species adequate to the environment being evaluated (and of long-term), for a more realistic ecological risk assessment of contaminated areas. |
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| Autores principais: | Araujo, Giuliana Seraphim de |
| Assunto: | Aphnia magna Daphnia similis Lead Mancozeb Multi-generation Pulse exposure |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Anthropogenic pressure negatively affects natural environments through the introduction of various types of stressors, from chemical, physical or biotic. Different species may present different sensitivities to such stressors, therefore, this research evaluated the sensitivity of two monophyletic species of daphnids, the tropical Daphnia similis and the model temperate species Daphnia magna to a lead (Pb) exposure, as well as combined with the fungicide mancozeb. Moreover, since aquatic organisms may be exposed for long periods, or pulse exposures, the experimental design used was based on a multi-generation exposure to evaluate offspring sensitivity/fitness, sensitivity and possible recovery through generations. The main goals of this study were: 1) Compare the toxicity of chemical compounds to two daphnid species, representing different climate regimes 2) Compare the effects of Pb between species in a long-term exposure, for more realistic responses 3) Estimate if Pb exposure would affect the sensitivity to other chemicals (e.g. pulse exposure), 4) Evaluate if food quantity affect organisms’ sensitivity to long-term exposures and, 5) Assess organisms’ recovery after a generational Pb exposure. In this context, D. magna presented a lower Pb sensitivity than D. similis, and mancozeb triggered opposite outcomes for the two species tested. The nine generation Pb exposure indicated a diminished Pb sensitivity for both species. A lower mancozeb sensitivity for Pb exposed organisms occurred for D. magna, while D. similis showed an opposite response. The generational assay indicated an enhanced rate of population increase (r) for both species, however, enhanced feeding rate occurred only for D. similis. Other contrasting effects among species caused by a long-term Pb exposure was seen for the Net Reproductive Rate (R0) which was not affected for D. magna and was diminished for D. similis. Meanwhile, early reproduction, reduced lifespan and AChE activity were shown for D. magna but not for D. similis. No disparity was shown between species considering adverse Pb effects. Generational Pb exposure led to carapace malformations, possible Pb granules in neonates’ dorsal region, reddish extremities in neonates (possibly indicating increased haemoglobin content). Considering reproduction, negative effects occurred such as male production, ephippias (or dormant haploid egg), eggs color variation (green and white) and abortion. Pb accumulation in D. magna through generations presented a faster and saturated Pb accumulation under usual food and a gradual concentration increase under food restriction, with a successful recovery (both food regimes). Pb exposure presented a general pattern of D. magna failed retrieval (may be due to ephigenetics) and D. similis successful retrieval (phenotypic acclimation) to levels similar to control (successful) organisms. The effect of Pb on reproduction, respiration, induction of malformation, and other adverse effects suggests that a chronic generational exposure can be harmful to both Daphnia species. The most important highlights of this study were; 1) Daphnia magna and Daphnia similis are capable of diminishing Pb sensitivity across a long-term Pb exposure, 2) Pb pre-exposure can affect daphnids’ sensitivity to other chemicals, 3) Pb exposure may increase the population of acclimated organisms in natural habitats, 4) Both species differ regarding recovery (epigenetics or physiological acclimation), 5) Different responses occur in single and generational exposures from monophyletic species (especially under oligotrophic media, typical of natural habitats). These results indicate the importance of accomplishing ecotoxicological assays with species adequate to the environment being evaluated (and of long-term), for a more realistic ecological risk assessment of contaminated areas. |
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