Arthropod assemblages in vegetative vs. humic portions of epiphyte mats in a neotropical cloud forest

Epiphyte mats (contiguous pieces of live and dead epiphytes perched upon branches of trees) are a conspicuous component of tropical cloud forests and harbor diverse meso- and microarthropod communities. We investigated differences in arthropod assemblage structure between the vegetative (green) and humic (brown) portions of epiphyte mats in a lower montane forest in Monteverde, Costa Rica. Because of qualitative differences between the two substrates, we hypothesized that they would support different arthropod communities and that variation in community parameters would be linked to the quantity of brown material present in a mat sample. The green fraction contained twice as many individuals and species per gram dry mass than the brown fraction. Morphospecies composition was very similar between green and brown portions, but the relative abundance of several taxa differed significantly between the substrates. Contrary to our prediction, total arthropod abundance and richness in a sample were not correlated with the proportion of brown material present. In laboratory trials, the most common morphospecies of oribatid mite in this system showed a preference for brown substrates.     

Irreversibility of sulfate sorption on goethite and hematite

Sulfate ion adsorption and desorption experiments carried out on synthetic goethite and hematite and natural hematite show adsorption to be a highly irreversible reaction. All oxides showed an increase in sulfate ion adsorption with decrease in pH. Only a small fraction of sorbed sulfate was desorbable after 48 hr, and only at a pH of 3. Extreme irreversibility of sulfate sorption on these common soil minerals suggests that adsorbed sulfate is more immobile in watersheds than previously considered and that recovery models which inherently assume reversibility may need to be modified.     

High pressure liquid chromatographic determination of zearalenone in chicken tissues

A method is reported for the extraction and analysis of zearalenone in chicken fat, heart muscle, and kidney tissue by using high pressure liquid chromatography (HPLC). Zearalenone is extracted with acetonitrile, cleaned up with hexane, and extracted further with ethyl acetate. Zearalenone is determined by HPLC using a reverse phase radial compression separation system, an ultraviolet absorbance detector, and a mobile phase of acetonitrile-water (60 + 40) (v/v). Recoveries of zearalenone added at levels from 50 to 200 ng/g are in the range 82.6-95.1%.     

Toxigenic type D Pasteurella multocida in New South Wales pig herds—prevalence and factors associated with infection

Between March and July 1987, a study was undertaken to determine the prevalence of and factors associated with toxigenic type D Pasteurella multocida infection in New South Wales pig herds. Toxigenic type D P. multocida was isolated from the nasal cavities of pigs in one (2%) of 50 randomly selected herds. Toxigenic isolates were also recovered from 2 (8%) of a separate group of 25 herds that had purchased pigs from a known infected piggery in South Australia (herd SA). Snout abnormalities were present in 9.4%, 3.2% and 1.8% of grower pigs in the 3 affected herds. Isolation of toxigenic P. multocida was significantly associated (p less than 0.0001) with the occurrence of clinically affected pigs in the herd. Purchase of at least 5 pigs from herd SA was associated with an elevated risk (p less than 0.05) of isolation of toxigenic P. multocida.