Clock-shift experiments with Savannah sparrows, Passerculus sandwichensis, at high northern latitudes

Orientation can be difficult for nocturnal bird migrants at high northern latitudes because of the large changes of magnetic declinations, rapid longitudinal time-shifts experienced during a long-distance flight and the invisibility of stars during the polar summer. Both sunset cues as well as geomagnetic cues have been shown to be of great importance in the orientation system of Savannah sparrows, Passerculus sandwichensis. We used clock-shift experiments to investigate whether geomagnetic and sunset cues were used for migratory orientation by wild-caught young Savannah sparrows at high geomagnetic latitudes in Northern Canada. We exposed birds to a 4-h slow clock-shift, expecting a 60° clock-wise shift in orientation after the treatment. Under natural clear skies in the local geomagnetic field, the birds responded by showing a significant axial mean orientation directed towards the position of the setting sun in the NW and towards their preferred migratory direction in the SE. After exposure to the clock-shift for 6 days and nights the birds showed a clear response to the treatment and shifted significantly towards NNE. Birds that first oriented towards NW in the experiments before clock-shift tended to shift clock-wise, thus reacted to the clock-shift in the expected way. The reaction of the individual birds that originally oriented towards SE seems to vary. In summary, our birds did not select a constant angle (menotaxis) in relation to the sun's position during the experiments, but presumably were affected by the sun showing phototaxis or followed their magnetic compass. Possible explanations of the unexpected experimental results are discussed. Electronic Publication     

Coefficient of variation of sea surface temperature (SST) as an indicator of coral bleaching

Coral bleaching has become a major problem on reefs around the world in recent decades. It is believed that mean temperature alone is the primary force driving this ecological phenomenon. We propose that variance in temperature in the short term is just as important as the mean. Thirty years of daily sea surface temperature (SST) data have been collected by the University of Puerto Rico at Mayaguez Marine Laboratory in La Parguera, PR. These data were collated and analyzed initially (by Amos Winter) for their relationship to coral bleaching in this area. We found that the data fell into three categories: high mean temperatures associated with severe bleaching, cooler mean temperatures associated with no bleaching, and years of high SSTs but with no coral bleaching. Here, we examined the relationship between mean temperature during those months in which bleaching occurred, temperature variance (as measured by standard deviation), and coefficient of variation (CV; i.e., SD standardized by the mean). We also derived a critical threshold temperature and level of resolution in time for calculating these statistics to clearly describe the circumstances of bleaching versus non-bleaching events, particularly at marginal bleaching temperatures. These characteristics were compared for the four warmest months of the year (July–October) for four warm bleaching years (1969, 1987, 1990, and 1995), four cool non-bleaching years (1984, 1985, 1986, and 1988), and two warm non-bleaching years (1994 and 2000). No relationship was found between the mean SST and SD in terms of predicting bleaching. The two primary statistics which, in concert, did indicate bleaching, however, were the short-term, biweekly mean temperature and its the associated CV. Bleaching occurs in association with both high temperatures and a high CV. The CV becomes a critical determinant of bleaching only when temperatures are ∼29.1–29.8°C. The warm, non-bleaching years were generally characterized by a CV of < 1.9 and a temperature range between 28.5 and 29.9°C. We conclude that increased mean SSTs alone are not sufficient to induce coral bleaching; a high variance in SST at marginal, lower bleaching temperatures can induce bleaching, and likewise, a low variance of such will not induce bleaching. This variance is most clearly described by the CV.     

Ingestion rate,assimilation efficiency and energy balance in Mytilus chilensis in relation to body size and different algal concentrations

Basing on a quantification of filtration, ingestion, assimilation, biodeposition, excretion and respiration rate, energy budgets were established in Mytilus chilensis Hupé in relation to body size and three different food concentrations of the unicellular green alga Dunaliella marina. The present quantifications revealed that in M. chilensis the ingestion rate only increases slightly with an increase in food concentration which, however, is counterbalanced by a significant decrease in assimilation efficiency in such a way that assimilation rate finally is nearly constant and independent of the food concentrations tested. The quantifications of these results are given by the a-values of the general allometric growth equation P=aW^b relating the energy disposable for growth and reproduction (P; cal d^-1 to body size (W; dry-tissue wt, g). The best energy budget was obtained at the lowest food concentration tested (0.8 mg algal dry wt l^-1; at 12°C and 30 S) with an a-value of 58.8, while the energy budget at the highest food concentration (2.14 mg l^-1) was only slightly lower with an a-value of 49.8; the b-values were 0.49 and 0.51, respectively. The net growth efficiencies (K₂) decreased with increasing body size (from 20 mg to 3 000 mg drytissue wt) from 76.7 to 47.9% at the lowest food level and from 72.6 to 44.0% at the highest food level tested. These relatively high net growth efficiencies seem to reflect optimal experimental conditions. Furthermore, by a comparison of estimated growth (calculated on the basis of the best energy budget) with growth actually quantified in culture raft mussels in the south of Chile during the highest production period of the year, it is obvious that the energy budgets established really reflect the conditions experienced by the mussels in their natural environment.This research was supported by grants S-80-3 and C-80-1 of the D.I.D.-UACH, by CONICYT, Found. Volkswagenwerk, Found. Fritz-Thyssen, by the GTZ, DFG and by the DAAD     

Target-site sensitivity in a specialized herbivore towards major toxic compounds of its host plant: the Na+K+-ATPase of the oleander hawk moth (Daphnis nerii) is highly susceptible to cardenolides

The caterpillars of the oleander hawk moth, Daphnis nerii (Linnaeus, 1758) (Lepidoptera: Sphingidae) feed primarily on oleander (Nerium oleander). This plant is rich in cardenolides, which specifically inhibit the Na⁺K⁺-ATPase. Since some insects feeding on cardenolide plants possess cardenolide-resistant Na⁺K⁺-ATPases, we tested whether D. nerii also possesses this strategy for circumventing cardenolide toxicity. To do so, we established a physiological assay, which allowed direct measurement of Na⁺K⁺-ATPase cardenolide sensitivity. Using Schistocerca gregaria, as a cardenolide-sensitive reference species, we showed that D. nerii Na⁺K⁺-ATPase was extremely sensitive to the cardenolide ouabain. Surprisingly, its sensitivity is even higher than that of the cardenolide-sensitive generalist, S. gregaria. The presence or absence of cardenolides in the diet of D. nerii did not influence the enzyme’s cardenolide sensitivity, indicating that target-site insensitivity is not inducible in this species. However, despite the sensitivity of their Na⁺K⁺-ATPase, caterpillars of D. nerii quickly recovered from an injection of an excessive amount of ouabain into their haemocoel. We conclude that D. nerii possesses adaptations, which enable it to feed on a cardenolide-rich diet other than that previously described in cardenolide specialized insects, and discuss other potential resistance mechanisms.     

Sulphur compounds—their environmental aspect and their elimination from waste water

The sulphur content of domestic waste water is similar to its phosphorus and nitrogen content. In conventional treatment processes sulphur compounds are converted to sulphate, thus all reaching the recipients and the oceans. In the aquatic metabolic cycle sulphate then acts as a catalyst towards anaerobiosis. Therefore, besides its efforts for removal of other nutrients, waste water technology should look for possibilities of minimizing the discharge of sulphurous effluents into the water course. Here, a new treatment process for sulphur elimination is introduced, the Root Zone method.     

Fight or flight? A geographic mosaic in host reaction and potency of a chemical weapon in the social parasite <Emphasis Type="Italic">Harpagoxenus sublaevis</Emphasis>

Ant social parasites use chemical warfare to facilitate host colony takeover, which is a critical but recurring step in their life cycle. Many slave-making ants use the secretion of the Dufour gland to manipulate host behaviour during parasitic nest foundation and slave raids. Harpagoxenus sublaevis applies this chemical weapon onto defending Leptothorax host workers, which elicits deadly fights amongst them. Host species are expected to evolve counter-adaptations against this behavioural manipulation and in this study we investigated the geographic structure of this co-evolving trait. We compared the effectiveness of the parasitic gland secretion from different H. sublaevis populations in host colonies from various sites and analysed the occurrence of local adaptation. The two host species L. muscorum and L. acervorum generally showed different responses to the parasites’ chemical weapon: L. acervorum attacked nestmates treated with Dufour gland secretion, while L. muscorum workers fled. Flight, instead of intraspecific fights, is an adaptive host reaction as it results in fewer host fatalities during raids. Beside interspecific host differences, we found a geographic mosaic of host resistance: parasites from a German population strongly manipulated the behaviour of both sympatric Leptothorax populations. Russian or Italian hosts instead did not react with intracolonial aggression, but fled when confronted with the gland secretion of their sympatric parasite. Not only variation in host resistance explains differences in the effectiveness of the parasitic gland secretion but also interpopulational differences in its chemical composition, which were revealed by gas chromatography and mass spectrometry.     

Recycling-oriented characterization of small waste electrical and electronic equipment

As a result of the continuous change in the design and function of consumer electrical and electronic products, the mechanical and material properties of the obsolete products, called waste electric and electronic equipment (WEEE), are highly variable. The variability within WEEE is explained by the number of different appliances, and the heterogeneity in composition of any given appliance.This paper reports on an extended investigation of the properties of WEEE, in particular small appliances. The investigation focuses on the analysis of the composition of about 700 single appliances. Firstly, analytical methods to characterize the waste equipment are described. The results of the experimental analyses show that the mechanical properties, the material composition, the polymer composition and the chemical composition of WEEE vary not only between equipment types with different functions, but also between single appliances within one equipment type. Data on hazardous and valuable substances in selected equipment types are presented.Using detailed data on the composition of individual appliances to calculate rates of recovery for assumed recycling processes demonstrates that the performance of recycling processes depends strongly on the composition of WEEE. Recycling-oriented characterization is, therefore, a systematic approach to support the design and the operation of recycling processes.     

Application of decision tools to ethical analysis in biodiversity conservation

Achieving ethically responsible decisions is crucial for the success of biodiversity conservation projects. We adapted the ethical matrix, decision tree, and Bateson's cube to assist in the ethical analysis of complex conservation scenarios by structuring these tools so that they can implement the different value dimensions (environmental, social, and animal welfare) involved in conservation ethics. We then applied them to a case study relative to the decision-making process regarding whether or not to continue collecting biomaterial on the oldest of the two remaining northern white rhinoceroses (Ceratotherium simum cottoni), a functionally extinct subspecies of the white rhinoceros. We used the ethical matrix to gather ethical pros and cons and as a starting point for a participatory approach to ethical decision-making. We used decision trees to compare the different options at stake on the basis of a set of ethical desiderata. We used Bateson's cube to establish a threshold of ethical acceptability and model the results of a simple survey. The application of these tools proved to be pivotal in structuring the decision-making process and in helping reach a shared, reasoned, and transparent decision on the best option from an ethical point of view among those available.