Biomineralization markers during early shell formation in the European abalone <Emphasis Type="Italic">Haliotis tuberculata</Emphasis>, Linnaeus

Larval shell formation was investigated in the European abalone Haliotis tuberculata. Stages of mineralization as well as enzymatic and endocrine biomarkers were monitored throughout larval development, from hatching to post-larval stages. Polarized light microscopy and infrared spectroscopy analyses revealed the presence of crystallized calcium carbonate arranged in aragonite polymorphs from the late trochophore stage. A correlation between the main steps of shell formation and enzymatic activities of alkaline phosphatase and carbonic anhydrase was seen. The variations of these biologic activities were related to the onset of mineralization, the rapid shell growth, and the switch from larval to juvenile shell following metamorphosis. Furthermore, a strong increase in the level of calcitonin gene-related molecules was measured in post-larvae, suggesting that endocrine control takes place after metamorphosis. The changes measured for the three biomineralization markers together with mineralogical analysis allowed us to correlate physiologic mechanisms with early steps of abalone shell formation.     

Comparison of methods for leaching heavy metals from composts

This paper presents the determination of total iron, copper, zinc, chromium, nickel, lead, cadmium and mercury contents in the compost obtained from sorted municipal organic solid waste applying the following methods of sample mineralization: 40% hydrofluoric acid with preliminary incineration of a sample, a mixture of concentrated nitric(V) and chloric(VII) acids with preliminary incineration of organic matter and a mixture of nitric(V) and chloric(VII) acids without sample incineration. The speciation analysis of Tessier was used to estimate the bioavailability of the metals. Elution degrees of the mobile forms of the metals from the compost with 10% nitric(V) acid and 1 mol/dm(3) hydrochloric acid were compared. The contents of the elements in the eluates were determined applying atomic absorption spectrometry.     

Movement of foraging Tundra Swans explained by spatial pattern in cryptic food densities

We tested whether Tundra Swans use information on the spatial distribution of cryptic food items (below ground Sago pondweed tubers) to shape their movement paths. In a continuous environment, swans create their own food patches by digging craters, which they exploit in several feeding bouts. Series of short (<1 m) intra-patch movements alternate with longer inter-patch movements (>1 m). Tuber biomass densities showed a positive spatial auto-correlation at a short distance (<3 m), but not at a larger distance (3-8 m). Based on the spatial pattern of the food distribution (which is assumed to be pre-harvest information for the swan) and the energy costs and benefits for different food densities at various distances, we calculated the optimal length of an inter-patch movement. A swan that moves to the patch with the highest gain rate was predicted to move to the adjacent patch (at 1 m) if the food density in the current patch had been high (>25 g/m2) and to a more distant patch (at 7-8 m) if the food density in the current patch had been low (<25 g/m2). This prediction was tested by measuring the response of swans to manipulated tuber densities. In accordance with our predictions, swans moved a long distance (>3 m) from a low-density patch and a short distance (<3 m) from a high-density patch. The quantitative agreement between prediction and observation was greater for swans feeding in pairs than for solitary swans. The result of this movement strategy is that swans visit high-density patches at a higher frequency than on offer and, consequently, achieve a 38% higher long-term gain rate. Swans also take advantage of spatial variance in food abundance by regulating the time in patches, staying longer and consuming more food from rich than from poor patches. We can conclude that the shape of the foraging path is a reflection of the spatial pattern in the distribution of tuber densities and can be understood from an optimal foraging perspective.     

Multiple paternity in meadow voles (Microtus pennsylvanicus): investigating the role of the female

Multiple paternity in single litters conceived in the wild was recently demonstrated in meadow voles (Microtuspennsylvanicus). In this study, we used an experimental approach (males tethered and females allowed to mate freely with one or several males) to investigate the role of female meadow voles in multiple paternity. We found that among 29 (of 39) females that copulated during our experiment, 79.3% chose to mate with more than one male. Female behavior in meadow voles thus clearly promotes multiple paternity and their role is an active one. Some of the hypotheses explaining promiscuity in meadow voles should be reconsidered in light of this result. We do not know the primary determinant of female mate choice, but male body mass played a secondary role in driving female preferences. The partial dependence between male body mass and female choice, coupled with the active role played by females, indicates that intersexual selection has the potential for reinforcing the effects of intrasexual selection (male-male dominance relationships) in this species. Finally, we demonstrate that the time period over which tests are conducted is an important part of the design of experiments aimed at understanding the role of females in multiple paternity. Received: 14 April 1998 / Accepted after revision: 12 September 1998     

Gill structure in Lucina pectinata (Bivalvia: Lucinidae) with reference to hemoglobin in bivalves with symbiotic sulphur-oxidizing bacteria

Lucina pectinata is a large tropical Lucinidae which is characterized by abundant tissue hemoglobin in its deep-red gills. In the present paper, hemoglobin is described as being located in cytoplasmic dark patches of the bacteriocytes together with a cystine-rich protein. Large microbodies contain a non-hemoglobin heme-compound which is identified with a previously described non-protein-bound hematin; however, it has not been established whether this heme is involved in a sulphur-oxidizing system or represents a catabolic by-product of hemoglobin. Electron-lucent vesicles are associated with the basal microbodies but their function is, so far, unknown. In addition, the bacteriocytes have been observed to have direct contact with sea water, modulated by large intercalary cells which overlap the bacteriocytes on their margin. Such relationships between bacteriocytes and intercalary cells, as well as their cytological features, are different from those observed in lucinid species inhabiting sea-grass beds, but very similar to those observed in Calyptogena magnifica. From the congruence between the shallow-water Lucinidae L. pectinata, inhabiting mangrove swamps, and the deep-sea Vesicomyidae C. magnifica, found at hydrothermal vents, we conclude that such features are likely to be adaptative to high-sulphide environments, notwithstanding the phylogenetic distance.     

Potential of Pulsed Light to Inactivate Bacteriophage MS2 in Simple Liquid Medium and on Complex Foodstuffs

The virucidal efficacy of a pulsed light treatment applied to viral suspensions, glass beads and herb powders was studied for the F-RNA bacteriophage MS2. The experimental results obtained demonstrated the high potential of this technology to efficiently decontaminate simple matrices but underlined the complexity of application to complex food matrices.     

The evolution of worker–queen polymorphism in Cataglyphis ants: interplay between individual- and colony-level selections

In many ants, young queens disperse by flying away from their natal nest and found new colonies alone (independent colony founding, ICF). Alternatively, in some species, ICF was replaced by colony fission, in which young queens accompanied by workers found a new colony at walking distance from the mother nest. We compared the queen morphology of Cataglyphis floricola, which disperses by fission, with that of its most likely living ancestor, Cataglyphis emmae, which disperses by ICF. As in other species, the transition from ICF to fission is associated with queen miniaturization. Interestingly, C. floricola presents two types of small queens: brachypters (with short non-functional wings) and ergatoids (worker-like apterous queens). Ergatoids are, on average, 2.8 mg lighter and have half the number of ovarioles than brachypters, which limits the advantage for a colony to produce ergatoids instead of brachypters. Furthermore, more ergatoids are produced than brachypters, but their individual survival rate is lower. During colony fission, 96% of the cocoons containing brachypters but only 31% of those containing ergatoids are transferred to the daughter nests where, after emergence, they compete for becoming the next queen. The remaining queen cocoons, which stay in the mother queen's nest, are eliminated by workers upon emergence, probably to maintain monogyny. This waste of energy suggests that producing ergatoids instead of brachypters is unlikely to increase colony efficiency. We argue that the evolution of ergatoids could derive from a selfish larval strategy, developing into worker-like queens in spite of the colony interest.     

Sectoralization of an Integrated Coastal Management Programme: A Case Study in Madagascar

This paper focuses on integrated environmental management and shows why emphasis should be put on implementation issues. The authors take the example of integrated coastal management (ICM) and analyse a case study they recently conducted in Madagascar, where an ambitious ICM programme is being implemented. They explain a strong perverse mechanism called sectoralization, which appears to threaten many integration efforts and is a good example of what is at stake with the implementation of the integration concept. They conclude especially that integrated environmental management should not be considered as the only modern form of environmental action, and that a certain type of case study is now needed to analyse existing environmental management systems before designing integration programmes.