Grower reported pesticide poisonings among Florida citrus fieldworkers

In a 1981 survey of 436 Florida citrus growers, 27 pesticide related poisoning incidents were reported that were to have taken place within one year of the interview date. From these reports it is possible to estimate that there are 376 citrus fieldworker related poisonings per year in Florida. This number of estimated poisonings may be developed into an incidence rate of 113 fieldworker poisonings per 10,000 fieldworkers.     

Resolving People-Park Conflicts through Negotiation: Reflections on the Richtersveld Experience

Protected areas in developing countries play a vital role in promoting the ideal of sustainable development.But 'people-park'conflicts are commonplace,threatening the future of these areas and the long term well-being of local communities. Surprisingly, little attention has been given to applying lessons learned in conflict studies to people-parkconflicts. In contrast to traditional adversarialresponses, negotiated approaches offer considerable potential for transforming people-park conflicts into mutually beneficial relationships.Experiencesin the Richtersveldregion of South Africa demonstrate the cardinal role negotiation can play in addressing key issues underlying people-park conflicts.     

Endocrine disruption of water and sediment extracts in a non-radioactive dot blot/RNAse protection-assay using isolated hepatocytes of rainbow trout

Goal, Scope and Background In order to evaluate the estrogenic activity of sediments and XAD water extracts of selected sites of the catchment area of the River Neckar, a river system in Southern Germany, an integrative assessment approach was used to assess the ecological hazard potential of endocrine-disrupting compounds in sediment and water. Methods The approach is based on estrogen receptor-mediated vitellogenin synthesis induced in isolated hepatocytes of rainbow trout and quantified in a non-radioactive dot blot/RNAse protection-assay in parallel to comprehensive chemical analyses of estrogenic substances. Results and Discussion Numerous investigated extracts revealed an estrogen activity comparable to that of the positive control (1 nM 17?-estradiol corresponding to 270 ng/L in the test medium). Based on a concentration factor of 30 in the extracts and a recovery of XAD resins of approximately 80 %, 17?-estradiol equivalent concentrations between 20 and 26.7 ng/L could be calculated downstream of a sewage treatment plant (< 0.1 ng/L for a reference site). A comparison of the bioassay-derived Bio-TEQs (toxicity equivalents) and the Chem-TEQs revealed a high correlation with a Pearson coefficient of 0.85, indicating that the same ranking of the samples could be obtained with respect to the endocrine disrupting potential with both chemical and bioanalytical analysis. However, the TEQ concentrations computed from chemical analyses were significantly lower than the bioassay-derived TEQ concentrations. In fact, in none of the samples, more than 14 % of the vitellogenin-inducing potency could be attributed to the substances (steroids, alkylphenols, bisphenol A, diethylstilbestrol) analyzed. A comparison of the endocrine disrupting potential of sediments extracted by the solvents acetone and methanol revealed lower biological effects for acetone-extracted samples. Possible reasons may be a masking of endocrine effects in acetone extracts by cytotoxicity, a low extraction efficiency of the solvent acetone, or anti-estrogen potencies of some extracted sediment compounds. Using a mass balance approach, the contribution of the compounds analyzed chemically (Chem-TEQs) to the total endocrine activity (Bio-TEQs) was calculated. Based on the very low detection limits, particularly of the steroids with their high TEF factors, results revealed that a calculation of the Chem-TEQs is associated with considerable scale inaccuracy: Whereas only 7-15 % of the biological effectiveness (Bio-TEQs) could be explained by endocrine substances identified above the detection limits, the assumption of concentrations slightly below the given detection limits would result in a significant over estimation (137-197 %) of the Bio-TEQs. Even the interassay variation of the dot blot assay with different fish donors for primary hepatocyte (factor 2 - 2.5) is relatively low, when compared to the large range of the Chem-TEQ concentrations (factor 20) obtained when applying different modes of calculation. Conclusions and Outlook Overall, only a minor portion of the endocrine activity detected by bioassays could be linked to compounds identified by chemical analysis. In vitro assays for assessment of endocrine activities are useful as sensitive integrating methods that provide quantitative estimates of the total activity of particular receptor-mediated responses. Although discrepancies may also result from different bioanalytical approaches, it is overall likely that bioanalytical and not chemical analytical approaches give the correct estimate of endocrine disrupting potencies in environmental samples. As a conclusion, assessment of endocrine disruption based on chemical analysis alone does not appear sufficient and further research into the spectrum of substances with potential endocrine activity as well as into additive or even synergistic effects in complex environmental samples is urgently needed.     

Trace metal contents of the pacific oyster (Crassostrea gigas) purchased from markets in Hong Kong

Arsenic, cadmium, chromium, and copper concentrations of the Pacific oyster,Crassostrea gigas, purchased from four different markets were determined in this project. In general, gill tissue had the highest proportion of metal contents (34%–67%) when compared with other tissue parts (mantle, viscera, and adductor muscle), except for arsenic, which showed the highest level in adductor muscle (44%). Smaller oysters (longitudinal length of soft body part less than 6 cm) had higher metal levels than larger ones (longitudinal length of soft body part more than 6 cm), except copper. None of the four metals examined showed an obvious seasonal trend, although cadmium levels seemed to be higher in autumn and winter months. Arsenic, cadmium, and copper levels in oysters purchased from different markets and different months obtained in the present study were higher when compared with past reports. Cadmium levels, as high as 10.98 mg/kg (dry weight basis) have been obtained. This approaches the safety limit that may be hazardous to human health. Continual monitoring of cadmium and other trace metals of toxicological significance to man in Hong Kong seafood is recommended.     

Nutrient transfer functions: the site of integration between feeding behaviour and nutritional physiology

Summary. We describe and extend a graphical approach to quantitative nutrition that focuses on the interplay between behavioural and physiological components of nutritional regulation. The site of integration is the nutrient transfer function, which is the function describing the time course of nutrient transfer between serially connected nutritional compartments (e.g., from the gut to the blood). The relationship between the shape of the nutrient transfer function and the temporal patterns of feeding determines the values of two key quantitative parameters of nutrition: the rate ('power') and the efficiency of nutrient acquisition. The approach can be extended to consider, in addition to the short-term behavioural and physiological decisions made by animals, some ecological determinants and longer-term, life history consequences of such decisions. Most importantly, this category of models can provide insights into the interplay among the various nutrients in an animal's diet. We illustrate this using hypothetical examples, and also present preliminary data for the power-efficiency relationships of protein and digestible carbohydrates in locusts. Finally, we consider existing evidence for the various means available to these and other insects for regulating such relationships. Received 24 September 1997; accepted 9 December 1997.     

Coordinating a group departure: who produces the piping signals on honeybee swarms?

A swarm of honeybees provides a striking example of an animal group performing a synchronized departure for a new location; in this case, thousands of bees taking off at once to fly to a new home. However, the means by which this is achieved remain unclear. Shortly before takeoff, one hears a crescendo of a high-pitched mechanical signal—worker piping—so we explored the role of this signal in coordinating a swarm’s mass takeoff. Specifically, we examined whether exclusively nest site scouts produce the worker piping signal or whether it is produced in a relay or chain reaction fashion. We found no evidence that bees other than the scouts that have visited the swarm’s chosen nest site produce piping signals. This absence of relay communication in piping suggests that it is a signal that only primes swarms for takeoff and that the release of takeoff is triggered by some other signal or cue; perhaps the takeoff of bees on the swarm periphery as they reach flight temperature in response to piping.     

Disease prevention and resistance in social insects: modeling the survival consequences of immunity,hygienic behavior,and colony organization

Understanding the origin of disease resistance in social insects is difficult due to the lack of well-established phylogenies of presocial and eusocial species and the absence of extant basal and intermediate forms. Moreover, comprehensive accounts of infection-control traits in social insect lineages are not available. Therefore, to explore the evolution of pathogen control in social insects we used cellular automata models to analyze the efficacy of immunity and nest hygiene, which we assumed were basal traits, and allogrooming, which likely followed the transition to eusociality, and their interactions with colony demography and patterns of worker spatial distribution. Models showed that nest hygiene provided an immediate survival benefit and that immunity lowered overall disease susceptibility under both constant and periodic exposure scenarios. Allogrooming increased survivorship in chronically challenged colonies but also increased pathogen transmission rates under conditions of periodic exposure. Colonies having demographies biased towards young or old individuals had slightly higher mortality than those with heterogeneous demographies. The distribution of older individuals relative to the nest center had no significant effect on susceptibility and provided only a minor survival advantage. Models indicated that nest hygiene and immunity function on different temporal scales and can interact with demography to lower disease risks. Our results suggest how infection control systems in social insects could have been built upon the inducible immune defenses and nest hygienic behaviors of solitary and presocial ancestors and served as important preadaptations to manage disease exposure and transmission in colonies of eusocial species.     

Diet quality affects an attractive white plumage pattern in dark-eyed juncos (Junco hyemalis)

Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.     

Organic contaminants and trace metals in flounder liver and sediment from the Amsterdam and Rotterdam harbours and off the Dutch coast

Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenylethers (PBDEs), nonylphenols], organotin compounds and trace metals (cadmium, chromium, mercury and zinc) were determined in flounder (Platichthys flesus) liver and sediment from the Amsterdam harbour (North Sea Canal) and Rotterdam harbour (Euromonding) and off the Dutch coast between the Amsterdam and Rotterdam harbour mouths in order to assess the level of contamination in these harbours and to study contamination gradients.