Wave action and competitive interaction between the invasive mussel Mytilus galloprovincialis and the indigenous Perna perna in South Africa

On the south coast of South Africa, the invasive alien mussel Mytilus galloprovincialis shows partial habitat segregation with the indigenous mussel Perna perna. P. perna predominates in the lower mussel zone and M. galloprovincialis in the upper zone, with mixed beds where the two overlap. We examined competitive interactions between these species by translocating mussels into small plots at high densities. Treatments involved different combinations of species and densities placed in each zone. Mortality was monitored regularly and at the end of each experiment, growth and condition index were measured. The experiment was attempted three times. The first two attempts were disrupted by wave action, especially winter storms, but provided information on species-specific effects of wave action. In experiment one, wave induced mortality decreased from a mean for both species of approximately 90% on the low shore to ca. 50% on the high shore, and was 15–30% lower for P. perna than M. galloprovincialis in each zone. In experiment two, M. galloprovincialis mortality was not affected by zone (Kruskal–Wallis test, P > 0.05), but was higher than P. perna mortality in the low zone (P < 0.05). P. perna survival was significantly (P < 0.05) lower on the high than mid and low zones, apparently due to the effects of greater emersion. Condition index showed a similar pattern, being lowest in the low zone for M. galloprovincialis and in the high zone for P. perna (3-way ANOVA, P < 0.05). Growth rates were fastest for both species in the low zone (Kruskal–Wallis, P < 0.05 in both cases). The third experiment was run for 12 months in the low zone only and provided evidence of intraspecific competition for P. perna and of interspecific competition. Condition was significantly greater for P. perna in all treatments (2-way ANOVA), as was growth (Kruskal–Wallis P < 0.05). Significant treatment effects indicated that P. perna had a negative effect on M. galloprovincialis survival (Kruskal–Wallis, P < 0.05). Again wave action was important; by the end of the experiment all mussels had been removed from plots stocked only with M. galloprovincialis. Thus P. perna improves survival of M. galloprovincialis on the low shore in the short term, by providing protection against wave action, but excludes it competitively in the longer term. The results show that partial habitat segregation is likely to be a permanent feature on the south coast, with M. galloprovincialis unable to dominate the low shore due to the effects of waves and competitive exclusion by P. perna. This study is the first attempt to examine the mechanisms of interaction between invasive and indigenous marine mussel species and provides evidence of the importance of environmental conditions in the mediation of this interaction.     

Human carcinogenesis by arsenic

Arsenic is one of the few human carcinogens for which there is not yet a reliable animal cancer model. As such, the classification of arsenic as a carcinogen is based upon data derived from human epidemiologic studies. Although the mechanisms of action of arsenic as a toxic agent have been known for many years, the inability to produce cancer with arsenic in laboratory animals has confounded the operational characterisation of arsenic as initiator, promoter, complete carcinogen, or cocarcinogen for humans. Arsenic is clearly a genotoxic agent that induces chromosomal aberrations, micronuclei and sister chromatid exchange in mammalian cells as well as neoplastically transforms Syrian hamster embryo cells; however, it is not a classical point mutagen. This paper reviews some of the scientifically based issues relating to arsenic and risk assessment.     

Vocal interactions in common nightingales (<Emphasis Type="Italic">Luscinia megarhynchos</Emphasis>): males take it easy after pairing

Seasonal patterns of bird song have been studied intensively with a focus on individual males. However, little is known about seasonal patterns of singing during vocal interactions between males. Vocal interactions have been shown to be important in sexual selection as males may signal aspects of motivation or quality. Here, we investigated in nightingales (Luscinia megarhynchos) whether a male’s behaviour in vocal interactions at different stages of the breeding season is influenced by its mating status. We examined how males that differ in their subsequent mating success respond to a non-interactive, nocturnal playback presented during the period of mate attraction and subsequently during the egg-laying period. We found that mated males overlapped fewer songs and had a lower song rate during the egg-laying period compared to their responses during the mate-attraction period, whereas unpaired males did not vary in their responses between the two periods. Our results suggest that mating status is a key factor affecting singing behaviour in vocal interactions and that a time-specific singing pattern like song overlapping is used flexibly during vocal interactions. Because song overlapping is thought to be a signal of aggression in male–male vocal interactions, it seems that males vary the level of aggression in vocal interactions according to their mating status and to the stage in the breeding season.     

Asymmetric sexual conflict over parental care in a biparental cichlid

Theoretical models predict that parents should adjust the amount of care both to their own and their partner’s body condition. In most biparental species, parental duties are switched repeatedly allowing for repeated mutual adjustment of the amount of care. In the mouthbrooding cichlid Eretmodus cyanostictus, terms are switched only once with females taking the first share. The timing of the shift of the clutch between mates strongly determines both partners’ brooding period and thereby their parental investment. Females signal their readiness to transfer the young several days before the male finally takes them, suggesting sexual conflict over the timing of the shift. In a lab experiment, we reduced the body condition of either the female or the male of a pair to test whether energy reserves affect the timing of the shift and whether female signalling behaviour depends on energetic state. Males with a lowered condition took the young later and incubated for a shorter period, which prolonged the incubation time of their female partners. When female condition was lowered, female and male incubation durations remained unchanged, although females signalled their readiness to shift more intensely. Our results suggest that males adjust their parental investment to own energy reserves but are unresponsive to their mate’s condition. Females appear to carry the entire costs for the male’s adjustment of care. We propose that intrinsic asymmetries in the scope for mutual adjustment of parental investment and the costs of negotiation crucially influence solutions of the conflict between sexes over care.     

Development of a new masters program for occupational physicians in Flanders

Background: discussions with occupational physicians and a postal survey identified the shortcomings of previous programs, mainly found in the fields of occupational hygiene, ergonomics, environmental health and management.Objectives of the new program: basic knowledge (see content), the development of problem solving skills, scientific and social attitudes.Content: first year: occupational health practice, occupational hygiene, epidemiology, work physiology, toxicokinetics and dynamics and in service training (4 weeks). Second year: occupational pathology, environmental health, ergonomics, social legislation, safety, management and in service training (4 weeks). The total study load is estimated at about 1600 hours per year.Methods: interactivity is stimulated by the introduction of interdisciplinary seminars, project work in groups and Socratic dialogue. The objectives, contents and teaching and student-evaluation methods of the separate items were defined before selecting teachers.Finality of the program: a masters title sufficient to practice occupational medicine in Belgium. A subsequent postacademic training of 2 years, while at work, will be required for the title of specialist in occupational medicine, valid at European Union (EU) level. It will include preparing and publically defending a thesis.Statement: The collaboration of ex-students working in the field is essential in the development and quality assessment of adequate teaching programs.     

Improving environmental management with full environmental cost accounting

Based on the most comprehensive field research ever conducted in corporate environmental management, this article reports on the integration of environmental impacts into product costing and cost management practices in organizations. It examines approaches for identifying and tracking current environmental costs related to both current and past production. It also develops the need and prospects for a complete analysis of future environmental impacts, including both costs and benefits, and the integration of these elements into a life-cycle costing or full environmental cost accounting model. The prospects for full environmental cost accounting and the related accounting issues are analyzed. Finally, the importance of full environmental cost accounting for improving corporate environmental performance, reducing corporate environmental impacts, and increasing long-term corporate profitability is discussed.     

Integrated Assessment of Swiss GHG Mitigation Policies After 2012

The residential sector presents a great potential for greenhouse gases (GHG) mitigation. We perform an integrated assessment of different mitigation policies for Switzerland focusing on the residential sector. We analyze the case of pure incentive taxes and technical regulations. For our analysis, we have coupled a general equilibrium model with a Swiss residential energy model. We find that a progressive GHG tax of more than 200 USD2000/tCO₂ eq is necessary to reach a target of 50% reduction of GHG emissions in 2050. Finally, we also find that efficiency-based technical regulations provide limited additional abatement incentives.