Scientific Literature #1
Pesticide is a substance used for destroying insects or other organisms harmful to cultivated plants or to animals.Amphibians have permeable skin that is highly absorbent, making them extremely susceptible to pollutants and pesticides.An abundance of scientific literature has demonstrated the negative effects of an array of commonly used pesticides on amphibians:delayed metamorphosis,immunosuppression, hermaphroditism, sex reversal, and outright mortality. Given the pervasiveness of pesticide applications, negative effects of pesticides could have an impact on amphibians around the world. Toxicity tests were conducted under highly artificial conditions to determine lethal concentrations (LC50). For first we used slightly longer exposure times (1016 d), low concentrations of the pesticide carbaryl (34% of LC504-d) and the results was that it killed 1060% of gray treefrog (Hyla Versicolor) tadpoles. Keep in mind if there was predator cues, the pesticide will be 24 times more lethal, thus killing 6098% of tadpoles. The results of this study illustrate the dangers of extrapolating short-term toxicity results to long-term population effects on nontarget organisms. Conditions of increased exposure times and predatory stress, current application rates for carbaryl can potentially devastate gray treefrog populations.
Moreover the predator-induced stress is ubiquitous in animals and carbaryl mode of action is common to many pesticides, these negative impacts may be widespread in nature.The dramatic changes in amphibian populations observed throughout the world likely have multiple causes, and all forward mechanisms deserve our attention because amphibians have permeable skin that is highly absorbent, making them extremely susceptible to pollutants and pesticides. It is crucial that investigators to continue to take in or contain as part of a whole in more natural experimental conditions to understand the full impact that pesticides may be having on our amphibian fauna.
In this case some methods were used. First and foremost an experiment was conducted in order to determine the chronic(longer-term) effect of carbaryl and predator stress on larval tree frog survival. Requirements needed were eggs from 10 pairs of amplecting tree frogs collected from a pond. The eggs were hatched in filtered tap water and then randomly assigned groups of 10 tadpoles (mean mass 6 1 SE in water 5 56 6 5 mg) to polyethylene tubs containing 10 liters of filtered tap water. Adsorption of carbaryl onto these plastic tubs has been found to be negligible (28). The tubs were placed on two shelves in two spatial blocks in a laboratory under a 15:9 h light:dark cycle. The concentration of a pesticide that is predicted to kill 50% of a test population within a given amount of time under given exposure conditions. Strains and plasmids. E. coli strains DH1 and C41 (DE3) were used as the wild type strain for all studies, except where indicated. Knockouts of fadE and fadE in DH1 were performed as previously described 24. A list of strains and plasmids constructed is given in Supplementary Table 1. Construction of plasmids was carried out with standard molecular biology methods. Growth and production parameters. Strains were cultivated in baffled flasks at 37 uC in M9 minimal medium supplemented with trace elements and the appropriate antibiotics (50 mg l21 ampicillin, 20mg l21 chloramphenicol, 5 mg l21
tetracycline, 100 mg l21 carbenicillin, 100 mg l21 spectinomycin and 50 mg l21
kanamycin). Pathway induction was achieved by the addition of 1 mM isopropylthiogalactoside (IPTG) at an absorbance of 0.51 measured at a wavelength of
600 nm (A600nm). For the thioesterase expression studies, 2% ethanol was added
and the post-induction temperature was 25 uC for production of FAEEs. Xylan
media was prepared by addition of 2%beechwood xylan and 0.2% glucose toM9
minimal media. Metabolites were identified and quantified by gas chromatography
mass spectrometry.The publication costs of this article were defrayed in part by page charge payment.This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. §1734 solely to indicate this fact. www.pnas.orgycgiydoiy10.1073ypnas.031076198 PNAS u February 27, 2001 u vol. 98 u no. 5 u 24912496