Acute toxicity and environmental risk of teflubenzuron to Daphnia magna, Poecilia reticulata and Lemna minor in the absence and presence of sediment.

This study aimed to estimate the acute toxicity of teflubenzuron (1-(3,5-dichloro-2,4-difluorophenyl)-3-(2,6-difluorobenzoyl)urea) (TFB) for Daphnia magna, Lemna minor and Poecilia reticulata, in the absence and presence of sediment; evaluate the effect of sediment on the TFB bioavailability; and to classify this insecticide according to its environmental poisoning risk for agricultural and aquaculture uses. The tests of TFB acute toxicity were conducted in static system in a completely randomized design with increasing TFB concentrations, and a control group. The TFB has been classified according to the estimated values of EC50 and LC50 by its acute toxicity and environmental risk. The sediment significantly reduced toxicity and bioavailability of TFB in water column. Therefore, the insecticide can be classified as being highly toxic to Daphnia magna, which means the agricultural and aquacultural uses of TFB pose a high risk of environmental toxicity to non-target organisms. However, it was practically non-toxic to L. minor and P. reticulata.

Larvicidal activity of the water extract of Moringa oleifera seeds against Aedes aegypti and its toxicity upon laboratory animals.

In this work, biological effects of the water extract of Moringa oleifera seeds (WEMOS) were assessed on eggs and 3rd instar larvae of Aedes aegypti and on its toxicity upon laboratory animals (Daphnia magna, mice and rats). Crude WEMOS showed a LC50 value of 1260microg/mL, causing 99.2 +/- 2.9% larvae mortality within 24 h at 5200microg/mL, though this larvicidal activity has been lost completely at 80 masculineC/10 min. WEMOS did not demonstrate capacity to prevent egg hatching. After extensive dialyses of the crude WEMOS into watersoluble dialyzable (DF) and nondyalizable (NDF) fractions, only DF maintained its efficacy to kill larvae. Acute toxicity evaluations on daphnids (EC50 of 188.7microg/mL) and mice (LD50 of 446.5 mg/kg body weight) pointed out to low toxicity. Despite the thymus hypertrophy, WEMOS revealed to be harmless in orally and subacutelytreated rats. In conclusion, WEMOS has thermostable bioactive compounds against Ae. aegypti larvae with apparent molecular mass lower than 12 kDa and moderately toxic potential.

Larvicidal activity of the water extract of Moringa oleifera seeds against Aedes aegypti and its toxicity upon laboratory animals

In this work, biological effects of the water extract of Moringa oleifera seeds (WEMOS) were assessed on eggs and 3rd instar larvae of Aedes aegypti and on its toxicity upon laboratory animals (Daphnia magna, mice and rats). Crude WEMOS showed a LC50 value of 1260µg/mL, causing 99.2 ± 2.9 percent larvae mortality within 24 h at 5200µg/mL, though this larvicidal activity has been lost completely at 80ºC/10 min. WEMOS did not demonstrate capacity to prevent egg hatching. After extensive dialyses of the crude WEMOS into watersoluble dialyzable (DF) and nondyalizable (NDF) fractions, only DF maintained its efficacy to kill larvae. Acute toxicity evaluations on daphnids (EC50 of 188.7µg/mL) and mice (LD50 of 446.5 mg/kg body weight) pointed out to low toxicity. Despite the thymus hypertrophy, WEMOS revealed to be harmless in orally and subacutelytreated rats. In conclusion, WEMOS has thermostable bioactive compounds against Ae. aegypti larvae with apparent molecular mass lower than 12 kDa and moderately toxic potential.

Neste trabalho, o extrato aquoso das sementes de Moringaoleifera (EASMO) foi avaliado quanto aos seus efeitos biológicos sobre ovos e larvas de Aedes aegypti no 3ºestágio de desenvolvimento e sua toxicidade sobre animais de laboratório(Daphnia magna, camundongos e ratos). O EASMO bruto revelou uma CL50 de 1.260 µg/mL, causando 99, 2 ± 2, 9 por cento de mortalidade em 24 h na concentração de 5.200 µg/mL, embora o mesmo não tenha sido capaz de impedir a eclosão dos ovos. A atividade larvicida extinguiu-se após aquecimento do extrato a 80ºC/10 min. Diálises sucessivas do EASMO bruto resultaram em duas frações solúveis em água (Fração dializável, FD; Fração nãodializável, FND), dentre as quais apenas a FD mostrou ação larvicida. Testes de toxicidade aguda realizadosem dáfnias (CE50 de 188, 7 µg/mL) e camundongos (DL50 de446,5 mg/kg de peso corpóreo) evidenciaram baixa toxicidade. Apesar da hipertrofia tímica, o EASMO mostrou ser atóxicoapós tratamento subagudo via oral em ratos. Conclui-se, portanto, que o EASMO apresenta substâncias com capacida de larvicida contra Ae. aegypti, as quais possuem massa molecular aparente menor que 12 kDa e potencial tóxico moderado.

Acute lethal and sublethal effects of neem leaf extract on the neotropical freshwater fish Prochilodus lineatus.

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 h LC(50) of neem leaf extract for juveniles P. lineatus was estimated as 4.8 g L(-1); the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L(-1) or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L(-1) and 5.0 g L(-1) neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L(-1). Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species.

Toxicidade aguda do inseticida Paration Metílico e do biopesticida azadiractina de folhas de Neem (Azadirachta indica) para alevino e juvenil de pacu (Piaractus mesopotamicus) / Acute toxicity of the insecticide methyl parathion and of the biopesticide azadirachtin from neem leaves (Azadiractha indica) to alevine and juvenile pacu (Piaractus mesopotamicus)

Os objetivos deste trabalho foram calcular a CL(I)50-96H do inseticida organofosforado paration metílico e do biopesticida azadiractina para alevinos e juvenis de pacu (P. mesopotamicus). Também pretendeu-se avaliar o efeito do peso corpóreo sobre a toxicidade aguda do paration metílico e do neem para o pacu, bem como classificar o risco ambiental do uso de paration metílico e do neem para o controle de parasitas e patógenos de pacu. Foram realizados dos experimentos, em condições laboratoriais, para a determinação da concentração letal (CL(I)50-96h). A CL (I)50-96h calculada do paration metilico foi de 3,97mg/L para os alevinos e de 9,89 mg/L para os juvenis. Para a azadiractina foi de 1,20mg/L para os alevinos e de 1,18mg/L para os juvenis. As concentrações de 1,0 mg/L de paration metilico para os alevinos e de 7,5 mg/L para os juvenis e as de 0,29 e 0,59 mg/L de azadiractina não provocaram mortalidade nos animais expostos e podem ser utilizadas como referência em estudos de controle de parasitas em pacu. O paration metilico foi menos tóxico para os alevinos e para os juvenis de pacu do que a azadiractina, indicando a necessidade de cuidados com a utilização de extratos aquosos de neem no ambiente aquático

Optimum maintenance techniques for carrying out bioassays with the freswater prawn Macrobrachium rosenbergii and acute toxicity of potassium dichromate / Optimum maintenance techniques for carrying out bioassays with the freswater prawn Macrobrachium rosenbergii and acute toxicity of potassium dichromate

Bioensaios foram conduzidos com pós-larvas do camarãode água doce Macrobrachium rosenbergii (peso médio = 0,023 ñ 0,009 g) com a finalidade de determinar as condições apropriadas para a manutenção destes organismos em testes de toxidade aguda. Os resultados indicaram que os camarões podem ser mantidos em jejum pelo período de 96 horas, sem que o hábito canibalístico seja estimulado, enquanto a aeração artificial nos aquários foi esencial para a manunteção dos níveis ideais de oxigênio na água durante este mesmo período. Testes de toxidade aguda (24h) também foram conduzidos com a substância de referência dicromato de potássio. As concentrações Letais Médias (CL50 -24h) foram estimadas de acordo com quatro métodos estatísticos: Binomial, Moving Average, Probit and Trimmed Spearman Karber, e variaram de 134,25 to 164,38 µg L -1 de cromo hexavalente. Distúrbios no comportamento natatório, perda de equilíbrio, ligeiras mudanças na pigmentação natural do corpo e um notável incremento na frequência de muda foram observados como sinais de intoxicação nos camarões