Comparative acute toxicity of neonicotinoid and pyrethroid insecticides to non‐target crayfish (Procambarus clarkii) associated with rice–crayfish crop rotations

BACKGROUND: Most insecticides used to control rice water weevil (Lissorhoptrus oryzophilus Kuscel) infestations are pyrethroids. However, pyrethroids are highly toxic to non‐target crayfish associated with rice–crayfish crop rotations. One solution to the near‐exclusive reliance on pyrethroids in a rice–crayfish pest management program is to incorporate neonicotinoid insecticides, which are insect specific and effective against weevils but not extremely toxic to crayfish. This study aimed to take the first step to assess neonicotinoids as alternatives to pyrethroids in rice–crayfish crop rotations by measuring the acute toxicities of three candidate neonicotinoid insecticides, clothianidin, dinotefuran and thiamethoxam, to juvenile Procambarus clarkii (Girard) crayfish and comparing them with the acute toxicities of two currently used pyrethroid insecticides, lambda‐cyhalothrin and etofenprox. RESULTS: Neonicotinoid insecticides are at least 2–3 orders of magnitude less acutely toxic (96 h LC₅₀) than pyrethroids to juvenile Procambarid crayfish: lambda‐cyhalothrin (0.16 µg AI L^?1) = etofenprox (0.29 µg AI L^?1) ? clothianidin (59 µg AI L^?1) > thiamethoxam (967 µg AI L^?1) > dinotefuran (2032 µg AI L^?1). CONCLUSION: Neonicotinoid insecticides appear to be much less hazardous alternatives to pyrethroids in rice–crayfish crop rotations. Further field‐level neonicotinoid acute and chronic toxicity testing with crayfish is needed. Copyright © 2009 Society of Chemical Industry     

Acute toxicity of chlorantraniliprole to non‐target crayfish (Procambarus clarkii) associated with rice–crayfish cropping systems

BACKGROUND: Chlorantraniliprole, a novel anthranilic diamide insecticide, was recently introduced into the United States where rice–crayfish crop rotations are practiced to control rice water weevil (Lissorhoptrus oryzophilus Kuschel) infestations. Chlorantraniliprole has high margins of mammalian safety and excellent insecticidal efficacy, but its toxicity to non‐target crayfish is uncertain. In this study, the acute toxicity of chlorantraniliprole to the red swamp crayfish Procambarus clarkii Girard was determined using aquatic and feeding assays. RESULTS: The aquatic 96 h median lethal toxicity (LC₅₀) data indicate that technical‐grade chlorantraniliprole is highly toxic (US EPA category) to crayfish with an LC₅₀ of 951 µg L^?1 (95% CL = 741–1118 µg L^?1). A no observed effect concentration (NOEC) of 480 µg L^?1 was recorded. Neither the 36 day chronic feeding study, where crayfish fed on chlorantraniliprole‐treated rice seed in aquaria, nor the 144 h acute feeding test, where crayfish fed on rice seeds treated with chlorantraniliprole, produced mortality or abnormal behavior. CONCLUSION: Chlorantraniliprole is three orders of magnitude less acutely toxic to P. clarkii than lambda‐cyhalothrin and etofenprox, two pyrethroid insecticides also used in rice, and is less likely to cause acute crayfish toxicity in rice pond ecosystems. Based on acute toxicity data, the use of chlorantraniliprole should be more compatible with rice–crayfish crop rotations than pyrethroids. Copyright © 2010 Society of Chemical Industry     

QUANTITATIVE TC-99m-MDP JOINT SCINTIGRAPHY IN A LENTIVIRUS-INDUCED ARTHRITIS OF GOATS

Caprine arthritis-encephalitis (CAE) is a lentivirus-induced disease of goats used as a model for the study of lentiviral infections. Tc-99m-MDP scintigraphy was investigated as a method to quantitate the severity of joint inflammation in CAE virus-induced arthritis in six goats (12 carpi). Carpal/metacarpal Tc-99m-MDP uptake ratio was compared to a clinical indicator of joint inflammation and histopathologic grading. Quantitative joint scintigraphy provided a better correlation (r = 0.75, p < 0.001) with histopathologic grading than the clinical indicator (r = 0.18, p > 0.10). Quantitative Tc-99m-MDP joint scintigraphy should be used when non-invasive quantitation of joint inflammation is needed for pathogenetic studies of CAE.     

Conservative management of a ruptured gastrocnemius muscle in a male llama.

Rupture of the gastrocnemius muscle was diagnosed in an obese llama using physical examination and ultrasound imaging. Conservative therapy consisting of the use of a cast to immobilize the affected limb permitted the muscle to heal. Only mild, residual gait abnormalities were observed on follow-up examination.     

Hydrogen-helium mixtures at megabar pressures: implications for jupiter and saturn

Models of Jupiter and Saturn postulate a central rock core surrounded by a fluid mixture of hydrogen and helium. These models suggest that the mixture is undergoing phase separation in Saturn but not Jupiter. State-of-the-art total energy calculations of the enthalpy of mixing for ordered alloys of hydrogen and helium confirm that at least partial phase separation has occurred in Saturn and predict that this process has also begun in Jupiter.     

Utilization of ascorbate-2-sulfate in fish

Although most vertebrate animals synthesize L-ascorbic acid (C₁), some animal species lack the ability to produce L-gulonolactone oxidase and are thus dependent upon a dietary source of vitamin C. Fish are unique among this latter group in that they store a chemically stable form of vitamin C and appear to metabolize this compound differently from other vitamin C-requiring organisms. Ascorbate-2-sulfate (C₂) contributes to total body stores of ascorbate, but the commonly used assays for ascorbate concentrations in tissues and body fluids do not generally measure C₂. An HPLC assay distinguishes between and measures both C₁ and C₂. Modification of the less exact but commonly used DNPH method can provide adequate data to estimate total vitamers C, C₁, and (by difference) C₂. Since vitamin C is a required component of feed for salmonids, catfish, eels, shrimp and carp, use of C₂ in feed formulation would provide a bioavailable form of ascorbate which is heat and water stable at pH 4–13.     

The cellular and molecular toxicity of sporidesmin

ABSTRACT

The fungal metabolite sporidesmin is responsible for the hepatogenous photosensitising disease facial eczema in livestock. Toxicity is due to a sulfur-bridged epidithiodioxopiperazine ring that has wide biological reactivity. The ways in which the toxin causes hepatobiliary and other tissue damage have not been established. Hypotheses include direct interaction with cellular thiols including protein cysteine residues or production of reactive oxygen species resulting in oxidative stress. Comparison with the cellular effects of the structurally related compound gliotoxin suggests additional mechanisms including interaction with cell adhesion complexes and possible downstream consequences for regulated necrosis as a response to tissue injury. Revision of hypotheses of how sporidesmin affects cells has the potential to generate new strategies for control of facial eczema including through identification of proteins and genes that are associated with resistance to the disease.