Comparison of naphthalene bioavailability determined by whole-cell biosensing and availability determined by extraction with Tenax

A rapid biological method for the determination of the bioavailability of naphthalene was developed and its value as an alternative to extraction-based chemical approaches demonstrated. Genetically engineered whole-cell biosensors are used to determine bioavailable naphthalene and their responses compared with results from Tenax extraction and chemical analysis. Results show a 1:1 correlation between biosensor results and chemical analyses for naphthalene-contaminated model materials and sediments, but the biosensor assay is much faster. This work demonstrates that biosensor technology can perform as well as standard chemical methods, though with some advantages including the inherent biological relevance of the response, rapid response time, and potential for field deployment. A survey of results from this work and the literature shows that bioavailability under non-equilibrium conditions nonetheless correlates well with K_oc or K_d. A rationale is provided wherein chemical resistance is speculated to be operative.     

Inheritance of dominance in honeybees (Apis mellifera capensis Esch.)

Summary Hierarchies in worker dominance are well developed in reproductive workers of the Cape honeybee (Apis mellifera capensis Esch.). Elements that influence worker dominance (trophallactic behaviour, fecundity, queen substance content) are mainly genetically determined. The estimated values for the heritabilities in the broader sense range from 0.27 to 0.89. This genetically based hierarchy leads to new insight into the theory of natural selection in honeybees. Besides selection at the colony level, or selection at the level of reproductives, natural selection also operates at the level of the individual worker bee within a colony.     

Ecology and characterization of yeasts from aquatic regions of South Florida

Mycological investigations, entailing over 400 samples from 120 separate collection stations, of the composite aquatic regions of southern Florida and adjacent areas have been developed. A collection of over 1000 yeasts, representing more than 50 taxa, has been characterized and studied. Highest yeast densities were found in freshwaters with the recovery of yeasts per sample decreasing from 100% to approximately 70% with lowered organic content, increasing salinity and remoteness from land. Average cell population densities, variety of species, and particularly the number of sexual yeasts, decreased in saline samples. The isolation media used were evaluated and have been discussed in terms of yeast densities obtained. Stritly oxidative species of Candida, Cryptococcus, and Rhodotorula and the sexual yeast, Debaryomyces hansenii, were the most widespread in all the habitas studied and the predominant forms in water of relatively low organic content. Selective survival of certain yeasts in the various aquatic environments was suggested. Definite distributional patterns were exhibited by various taxa and the possible existence of indicator species wa suggested. The systematics of the fungi have been reviewed at length and the significance of strain differences considered and discussed as related to the unique characteristics of the various ecological habitats.     

Application of headspace analysis and AOX-measurement to leachate from hazardous waste landfills

The applicability of headspace analysis for the quantitation of volatile organic compounds in leachates from hazardous waste landfills is investigated with respect to standard stability, leachate stability and reproducibility. Between the corresponding data sets, deviations at about 10 % are observed. Besides the analysis of the volatile leachate components, the sum parameters POX and AOX are determined for the leachate samples. From the POX-data, good agreements with the total organic chlorine determined by headspace analysis are received. For determination of AOX, two different methods are applied to the leachates and discussed with respect to the high concentrations of POX determined in all leachate samples.     

SMALL FISH MODELS FOR IDENTIFYING CARCINOGENS IN THE AQUEOUS ENVIRONMENT1

ABSTRACT: Contaminants in water and sediments can be carcinogenic to aquatic wildlife as well as humans. Identifying those carcinogens, however, is difficult because they often occur in low concentrations and exert their effects over a large part of the life span of affected organisms. Furthermore, the carcinogens are often components of complex mixtures. Recent studies suggest that laboratory-reared fish species might be well suited for testing water-associated and other carcinogens. Here, we review the principal carcinogen exposure methods that utilize small fish species or can be adapted to utilize small fish species to detect carcinogens in aqueous environments. Emphasis is placed on methods for which the end-point is tumor induction. The methods discussed are dietary exposures, skin painting, embryo microinjection, early life stage (pulse) exposures, static water exposures, flow-through exposures, and controlled field exposures. Early life stage exposures seem to have the greatest utility with regard to carcinogen sensitivity, ease of administration, disposal of test compounds, and economy of materials and effort. For certain types of carcinogens, however, long-term flow-through exposures are probably required. In summary, small fish carcinogenesis models offer an array of methodologies that can be utilized in a variety of combinations depending on compounds tested, exposure parameters employed, and end points sought.     

Effects of stage of colony cycle,context, and intercolony distance on conspecific tolerance by paper wasps (Polistes fuscatus)

Summary We observed in the field how resident females of the social wasp, Polistes fuscatus, treated female nestmates, non-nestmate first cousins, and unrelated non-nestmates. Behavioral observations were made 1, 3, 4, 6, 7, 8, and 11 weeks after the emergence of a colony's first workers. Resident females were highly tolerant of female nestmates but highly intolerant of unrelated non-nestmates throughout the post-worker-emergence phase of the colony cycle. First cousins were treated either highly tolerantly or highly intolerantly, although most cousins ( 63%) were treated highly intolerantly. The treatment of cousins suggests that they are treated either tolerantly (like nestmates) or intolerantly (like unrelated non-nestmates) depending on whether they fall above or below an acceptance threshold, respectively. Resident females did not significantly change their tolerance nestmates, first cousins, and unrelated females between different observation periods. However, all conspecifics were generally treated the most intolerantly 11 weeks post-worker-emergence, a time in the colony cycle when combs no longer contain brood. This decreased tolerance and its associated variance patterns late in the colony cycle are consistent with a more restrictive acceptance threshold. The optimal level of the acceptance threshold appears to be a compromise between the fitness consequences of accepting unrelated non-nestmates and rejecting one's nestmates. In a laboratory study, resident females were equally tolerant of female nestmates on and off the comb but significantly less tolerant of unrelated females on the comb than off the comb. Thus, females can modify their tolerance rapidly in different recognition contexts. In a second laboratory study, resident females were equally intolerant of unrelated females, regardless of whether they were from colonies 50 m or 50 km distant.Offprint requests to: G.J. Gamboa