Selective predation on mature male Byblis japonicus (amphipoda: Gammaridea) by the barface cardinalfish,Apogon semilineatus

Ontogenetic change of habitat depths of Nautilus pompilius in the Philippines (Tañon Strait) and Fiji is considered by comparing ¹⁸O/¹⁶O ratios in septa and cameral fluid of live-caught specimens and ambient sea-water. ¹⁸O values of cameral liquid become heavier with decreasing volume within a chamber, which may be due to isotopic fractionation during discharge across the siphuncular wall. All of the seven Philippine and Fiji specimens analyzed show a distinct change in ¹⁸O from light values in the first seven septa to heavier values in the succeeding septa. Two different isotopic temperature scales are obtained for the Fiji and Philippine populations, suggesting a differential vital effect of metabolism between them. Sightly light ¹⁸O values in Septa 1 to 7 and hatching at relatively high temperatures in aquaria both suggest that N. pompilius hatch at the shallowest depths within their inhabitable vertical range. Depths of postembryonic animals in the Philippines and Fiji waters estimated from the isotopic temperature-depth diagrams range from 120 to 160 m and from 440 to 520 m, respectively, both of which correlate well with capture records. More than several tens of small-scale ¹⁸O cycles are detected in the sequence of nacreous layers within the single septum of a submature Philippine specimen. This can be interpreted as reflecting daily vertical migration.     

Pastoral and environmental security in East Africa

The most vulnerable people in Third World countries are often accused of destroying forests and fragile ecosystems and of practising destructive forms of agriculture and animal husbandry. The key to environmental sustainability, however, lies in more reliable production and food security at the local level. This article focuses on individual and household security amongst dryland herders in East Africa. The most crucial aspect of pastoral viability is the maintenance of a balance between family herd and size of household. Risk-spreading, through dependence on relatives, the borrowing of animals, redistribution through marriage etc. is a general principle of social behaviour amongst these peoples. Consideration of local-level security, furthermore, reveals the connection between ecological stress and political conflict. Only by establishing secure access to food for individuals and families can sustainable development and political security, not only at the local but also at the national and international levels, be achieved.     

Analysis of two-way layout of count data with negative binomial variation

A number of methods has been proposed for dealing with single-factor or factorial experiments when the requirements for performing the normal theory analysis of variance procedure are not satisfied. This paper suggests the use of the likelihood ratio statistic for testing the main effects and the interaction between the factors in two-way layout of count data following negative binomial distributions with a common dispersion parameter. The likelihood ratio statistic for testing the equality of the dispersion parameters of several groups of count data is also derived. The methods is illustrated by an example concerning the study of spatial and temporal variation of bacterial counts.     

Soil fauna and soil microflora as possible indicators of soil pollution

Research on biological indicators of soil pollution is hampered by soil variability and temporal and spatial fluctuations of numbers of soil animals. These characters on the other hand promote a high biological diversity in the soil. A high diversity combined with persistent soil pollutants increases the chance to select good indicators. However research on these topics is still limited. Examples of specific indicators are the changed arthropod species patterns due to pesticide influence and the changed soil enzyme activity under the influence of specific heavy metals. Another approach is to look for organisms that give a general indication of soil pollution. In this respect the earthworm species Allolobophora caliginosa proved to be sensitive for different types of manure especially pig manure with copper, for sewage sludge, for municipal waste compost and for fly ash. A third way of indication is by organisms accumulating pollutants. For some heavy metals (Cd, Zn), earthworms are very efficient accumulators. More research is needed especially on the specific relation between biological responses and abiotic soil characteristics.     

Dose-time-response functions for toxic chemicals

In many situations, the effect of a toxic chemical on a biological system depends on both the intensity and the duration of exposure. The dependence on the time dimension can be the expression of a range of processes including the physical accumulation of toxic chemicals or their metabolites and the functional accumulation of damage. Measures and functions that have been used to describe this dependence are reviewed.Some of these functions are compared through a case study of the neurotoxicity of methylmercury. Use is made of data that indicates a dependency between the blood concentration at which monkeys were exposed and the length of time before damage was detected. Several exposure functions are fitted to these data and their appropriateness is compared. Using the most appropriate function, an exposure-response relationship is developed using probit analysis. An alternative data analysis procedure is also investigated. The apparent threshold after a 100 day exposure is estimated to be greater by a factor of 3–5 compared to the threshold for chronic exposure. Applying this factor to man, the blood concentration threshold for chronic exposure is estimated to be 40–170 ppb, a finding consistent with recent reports of neurological damage in humans exposed below the generally accepted threshold.     

The eolian sand problems arising from desertification

Eolian (wind blown) sand constitutes a very serious problem to development in sandy desert lands and causes equally serious problems in lands that are undergoing desertification. In this paper, eolian sand movement due to bulk movement such as sand dune and ripple movement, sand drift by saltation, and sand storms by strong winds are discussed. Associated problems such as eolian sand encroachment on highways, farms, communities and industrial complexes are also discussed and workable solutions are offered. Solutions include chemical stabilization of the surface grains, fences to trap the blown sand and vegetation to prevent soil deflation. Vegetation is emphasized and recommended as the ultimate viable solution to combat desertification and eolian sand problems.