Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC50 48 h for Daphnia similis of 5.1 ng L-1, LC50 96 h for Chironomus xanthus of 2.67 mu g L-1 and LC50 48 h for Danio rerio of 33 mu g L-1. (C) 2011 Elsevier Ltd. All rights reserved.

Skeletal abnormalities in humpback whales Megaptera novaeangliae stranded in the Brazilian breeding ground

Skeletal tissues of 49 humpback whales Megaptera novaeangliae that stranded between 2002 and 2011 along the Abrolhos Bank seashore and its adjacent waters in Brazil were studied. Twelve (24.5%) animals presented pathological changes in one or more bones. Degenerative changes and developmental malformations were most frequent (10.2% each), followed by inflammatory/infectious and traumatic lesions (8.2% each). Infectious diseases led to severe lesions of the caudal vertebrae of 2 whales. In one of these individuals, the lesions involved 6 caudal vertebrae, leading to ankylosis of 3 vertebrae. Degenerative changes were observed in the vertebral columns of 3 animals, involving the joints of 13 ribs of 1 individual, and in the humerus of 1 whale. Traumatic lesions, such as osseous callus in the ribs, were observed in 4 animals. In 1 whale, the rib showed severe osteomyelitis, possibly resulting from the infection of multiple fractures. Developmental abnormalities such as spina bifida on 3 cervical vertebrae of 1 whale, fusion of spinal processes on thoracic vertebrae of 1 individual and fusion of the first 2 ribs unilaterally or bilaterally in 4 animals were found. Chronic infectious conditions found in the axial skeleton may have restrained spinal mobility and had detrimental effects on the general health of the animals, contributing to stranding and death. To our knowledge, this is the first systematic study on skeletal lesions in stranded humpback whales.

Batrachochytrium dendrobatidis in amphibians confiscated from illegal wildlife trade and used in an ex situ breeding program in Brazil

This paper describes an outbreak of chytridiomycosis affecting a group of Dendrobates tinctorius, a Neotropical anuran species, confiscated from the illegal wildlife trade and housed in a private zoo in Brazil as part of an ex situ breeding program. We examined histological sections of the skin of 30 D. tinctorius and 20 Adelphobates galactonotus individuals. Twenty D. tinctorius (66.7%) and none of the A. galactonotus were positive for Batrachochytrium dendrobatidis (Bd). Multiple development stages of Bd infection were observed. The reasons for the interspecific difference in the rate of infection could not be determined, and further studies are advised. Because the examined population consisted of confiscated frogs, detailed epidemiological aspects could not be investigated, and the source of the fungus remains uncertain. The existence of ex situ amphibian populations is important for protecting species at higher risk in the wild, and ex situ amphibian conservation and breeding programs in Brazil may be established using confiscated frogs as founders. However, this paper alerts these programs to the urgency of strict quarantine procedures to prevent the introduction of potential pathogens, particularly Bd, into ex situ conservation programs.

Screening bacterial metabolites for inhibitory effects against Batrachochytrium dendrobatidis using a spectrophotometric assay

Certain bacteria present on frog skin can prevent infection by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), conferring disease resistance. Previous studies have used agar-based in vitro challenge assays to screen bacteria for Bd-inhibitory activity and to identify candidates for bacterial supplementation trials. However, agar-based assays can be difficult to set up and to replicate reliably. To overcome these difficulties, we developed a semi-quantitative spectrophotometric challenge assay technique. Cell-free supernatants were prepared from filtered bacterial cultures and added to 96-well plates in replicated wells containing Bd zoospores suspended in tryptone-gelatin hydrolysate-lactose (TGhL) broth medium. Plates were then read daily on a spectrophotometer until positive controls reached maximum growth in order to determine growth curves for Bd. We tested the technique by screening skin bacteria from the Australian green-eyed tree frog Litoria serrata. Of bacteria tested, 31% showed some degree of Bd inhibition, while some may have promoted Bd growth, a previously unknown effect. Our cell-free supernatant challenge assay technique is an effective in vitro method for screening bacterial isolates for strong Bd-inhibitory activity. It contributes to the expanding field of bioaugmentation research, which could play a significant role in mitigating the effects of chytridiomycosis on amphibians around the world.

Evaluation of the Sensitivity of Freshwater Organisms Used in Toxicity Tests of Wastewater from Explosives Company

Explosives industries are a source of toxic discharge. The aim of this study was to compare organisms sensitivity (Daphnia similis, Danio rerio, Escherichia coli and Pseudomonas putida) in detecting acute toxicity in wastewater from two explosives, 2,4,6-TNT (TNT) and nitrocellulose. The samples were collected from an explosives company in the Paraiba Valley, So Paulo, Brazil. The effluents from TNT and nitrocellulose production were very toxic for tested organisms. Statistical tests indicated that D. similis and D. rerio were the most sensitive organisms for toxicity detection in effluents from 2,4,6-TNT and nitrocellulose production. The P. putida bacteria was the organism considered the least sensitive in indicating toxicity in effluents from nitrocellulose.

Cylindrospermopsis raciborskii exudate-Cu complexes: impact on copper dynamics and bioavailability in an aquatic food chain

The increasing contamination of aquatic environments motivates studies on the interactions among natural dissolved organic matter, metals, and the biota. This investigation focused on the organic exudates of the toxic cyanobacteria Cylindrospermopsis raciborskii as a Cu carrier through a three-level aquatic trophic chain (bacteria, protozoa, and copepod). The effects of bacteria activity and growth on the metal-organic complexes were evaluated through changes in free Cu2+ ions, total dissolved, and total particulate Cu. To be sure that the added copper would be complexed to the exudates, its complexing properties were previously determined. The cyanobacteria exudate-Cu complexes were furnished to bacteria that were further used as a food source to the protozoan Paramercium caudatum. This was then furnished as food to the copepod Mesocyclops sp. The results showed that, in general, the cyanobacterial exudates decreased Cu bioavailability and toxicity to the first trophic level (bacteria), but because the heterotrophic bacteria accumulated Cu, they were responsible for the transference for the otherwise low availability metal form. Both the bacteria and protozoan organisms accumulated Cu, but no metal accumulation was detected in the copepods.