Effect of exposure time on the acute toxicities of permethrin, fenitrothion, carbaryl and carbofuran to mosquito larvae

Abstract

Static toxicity tests were used to assess the acute toxicity to third‐instar Aedes aegypti (L.) to short‐term exposures of five insecticides (technical permethrin, microencapsulated permethrin, fenitrothion, carbaryl, and carbofuran). Larvae were exposed to each insecticide for times of 0.25, 0.5, 1, 2, 4, 8, or 24 h, then transferred to clean water and reared to the adult stage. Technical permethrin was most toxic to Aedes aegypti, followed by fenitrothion, microencapsulated permethrin, carbofuran, and carbaryl (24 h LC50 values, based on survival to the adult stage, were 0.45, 3.1, 21.6, 90.0, and 510.0 μg/L, respectively). Acute toxicity increased with increasing exposure time to all five insecticides. However, the relationship between exposure time and acute toxicity differed among insecticides. The increase in acute toxicity was greater over short than over long exposures for technical permethrin, carbaryl, and carbofuran (LC50 values decreased 11.2 to 22.4‐fold over a 0.5‐ to 4‐h exposure, and 2.6‐ to 5.2‐fold over a 4‐ to 24‐h exposure). The opposite was true for microencapsulated permethrin (LC50 values decreased 3.6‐fold over a 0.5‐ to 4‐h exposure, and 6.2‐fold over a 4‐ to 24‐h exposure). Acute toxicity to fenitrothion increased proportionately with increasing exposure time. Some larvae recovered from immobilization following short (0.5‐ to 4‐h) exposures to technical permethrin, microencapsulated permethrin, carbaryl, and carbofuran (EC50 values based on immobilization immediately after exposure terminated were 0 to 15 times lower than corresponding LC50 values). However, ability to recover decreased with increasing exposure time such that no recovery from immobilization occurred after 8 or 24 h exposure. Larvae did not recover from immobilization following exposure to fenitrothion. These results indicate the need for a postexposure observational period to fully assess acute toxicity following exposure to insecticides.

Esfenvalerate toxicity to the cladoceran Ceriodaphnia dubia in the presence of green algae, Pseudokirchneriella subcapitata

“…In invertebrates, exposure to fenvalerate has been shown to reduce alarm response, hence increasing predation risk (Reynaldi et al 2011). Additionally in daphnids it has been shown that exposure to low doses of a toxicant can result in effects on fecundity and can cause delayed mortality (Coniglio and Baudo 1989;Parsons and Surgeoner 1991), therefore animals that were alive at the conclusion of our exposures would not have necessarily recovered. Esfenvalerate exposures in Medaka (O. latipes) affected both reproduction and hatching success (Werner et al 2002).…”

Toxicity analysis of freshwater and marine sediments with meio- and macrobenthic organisms: a review

“…The time of exposure to the test substance is a critical consideration in sediment tests, for extended exposure is associated with greater sensitivity Malueg et al ., 1984a, b ;LeBlanc & Surprenant, 1985 ;Ingersoll & Nelson, 1990 ;Parsons & Surgeoner, 1991) . Thus, the effect of small toxicant doses can sometimes be revealed in the form of sublethal effects after prolonged exposure .…”

GamTox: A Low-Cost Multimetric Ecotoxicity Test withGammarusspp. forInandEx SituApplication

“…studies, as usually the LC 50 s decrease with increasing exposure time, esp. during the first 48 h [7]. After application of a correction factor of 2 to the Daphnia magna studies, sensitivity shifted towards Daphnia magna in some cases.…”