Morphophysiological and behavioral changes mediated by deltamethrin in aquatic insects

• Ano de defesa: 2014
• Autor(a) principal: Gutiérrez López, Yeisson
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Insetos; Insetos aquáticos; Insetos aquáticos - Comportamento - Locomoção; Insetos aquáticos - Anatomia; Insetos aquáticos - Morfologia; Inseticidas - Toxicologia; Entomologia Agrícola
• Link de acesso: https://locus.ufv.br//handle/123456789/26687

Although there is already a considerable scientific framework on the lethal effects of insecticides on target organisms, there are few records of sublethal effects of these com- pounds and, in the case of aquatic insect fauna, this information is virtually nonexistent. Pyrethroids are potent neurotoxic insecticides that have sodium channels as their primary sites of action. These compounds are widely used in agriculture and in the control of insect vectors of disease, which has allowed that part of the molecules applied in the field end up reaching aquatic ecosystems. Aquatic insects are customarily used as bio-indicators of water quality, which make them excellent study models of the contamination of water bodies by deltamethrin. Within this context, this project was conducted to evaluate the morphophysiology of action as well as behavioral changes in aquatic insects triggered by sublethal exposure to deltamethrin. To this end, the mayflies Callibaetis radiatus were used in experiments aimed at ascertaining both the toxicity and the possible disturbances at cellular and tissue level in the nervous system and midgut resulting from exposure to deltamethrin, and heteropteran predators (Notonectidae), Buenoa tarsalis and Martarega bentoi, were used in experiments aimed to determine the toxicity of deltamethrin and pos- sible changes in swimming activity of these bugs when exposed to sublethal concentrations of this insecticide. Significant reductions in the survival of C. radiatus was observed at concentrations of deltamethrin ≥ 0.5 μg/L. Cytomorphological changes were light in the brain (presence of pyknotic nuclei) and severe in thoracic ganglia (neuronal vacuolization and deformation of bodies, appearance of voids between the perineurium and the cortical region, and the presence of pyknotic nuclei) and in the midgut (retraction of the muscular layer, cytoplasm vacuolization, disorganization of the nucleus and cytoplasm) of C. radi- atus when these insects were exposed to the sublethal concentrations 0.25μg/L. However, immunofluorescence and DNA integrity analysis showed that these changes did not cause cell death. In experiments with aquatic heteropterans, the results showed that B. tarsalis is a more sensitive species than M. bentoi to the presence of deltamethrin. The survival of these organisms was reduced at all concentrations tested, and short-term exposure to deltamethrin caused a change in the pattern of occupation of the water column. Such behavioral disturbances were more severe in females than in males of B. tarsalis, since the locomotory activity of the females was significantly reduced when exposed to deltameth- rin (0.05 μg/L). For the species M. bentoi, the exposure to deltamethrin did not incur in significant differences in the locomotion of these insects. Thus, our findings suggest that exposure to deltamethrin concentrations, even at low concentrations, affects the control of vital processes (metabolism) or behavior (eg, locomotion) of aquatic macroinvertebrates, which can incur in serious environmental imbalances.