Utilization of yolk reserves during post-embryonic development in three teleostean species: the sea bream Sparus aurata,the sea bass Dicentrarchus labrax,and the pike-perch Stizostedion lucioperca

A comparative study of the use of yolk reserves during post-embryonic development was performed on three teleostean fishes of aquacultural interest: the sea bream Sparus aurata, the sea bass Dicentrarchus labrax, and the pike-perch Stizostedion lucioperca. The first part of the work was devoted to the structural development of the periblast, the vitellus and the oil globule during the endotrophic and endo-exotrophic phases of larval life. Observations using transmission electron microscopy revealed a perivitelline circulation system closely related to the liver, and suggested an important function of the periblast in the utilization of reserves. In the second part of the study, cytochemical reactions revealed the way in which the reserves are resorbed. Glycogen contained in the periblast at hatching was utilized during the endotrophic period. The successive appearance of lipoprotein particles in the periblast endoplasmic reticulum, Golgi apparatus, and perivetelline circulation zone is consistent with the mobilization of yolk and oil globule components. Comparison of fed and fasting individuals revealed that fasting tended to slow down rather than increase the utilization of reserves.     

Seasonal variability of intertidal bacterial metabolism and growth efficiency in an exposed sandy beach during low tide

Benthic gross primary production (GPP) and community respiration (BCR) were regularly measured on sandy beach sediment during low tide in a megatidal ecosystem. These measurements were assessed during 2 years in situ within a benthic chamber simultaneously with bacterial production (BP). Results suggested that community respiration in Wimereux sandy beach sediments was probably dominated by bacterial respiration and that the estimated benthic bacterial growth efficiency (BGE) was highly variable. Although temperature significantly controlled both BP and BCR during low tide at the annual scale, the temperature effect on BGE was not significant. The instability and sediment erosion caused by the wave action and the tidal cycle were thus thought to influence the BGE. Since the sampling site is regularly affected by Phaeocystis foam deposit (enhancing the BCR and decreasing the BGE), and since GPP rates were highly variable and supported by high assimilation numbers (i.e., >1 mgC mgChla ⁻¹ h⁻¹), phytoplankton organic matter deposit following the immersion of the study site was thought to explain the BGE variability.     

Ontogeny of osmoregulation in the European sea bass Dicentrarchus labrax L.

 Under natural conditions, sea bass eggs hatch in the open sea and young-of-the-year sea bass are found close to estuaries and enter brackish and even freshwater lagoons in the Mediterranean and the eastern Atlantic. The ontogeny of osmoregulation in the European sea bass, Dicentrarchus labrax (Linnaeus, 1758), was studied in different developmental stages, from hatching to large juveniles, exposed to a range of salinities at 17 °C. The experiments were carried out from March to August 1998 in southern France. The type of hyper-hypo-osmotic regulation did not change during development. All stages hyper-regulated at low salinity (under 10–11‰) and hypo-regulated at higher salinities. The acquisition of the full ability to hypo-regulate occurred in four steps. Osmoregulatory capacity was size- and age-dependent and reached its maximum for fish 17–26 mm long, 63–86 days after hatching. The iso-osmotic salinity was 10.2–11.6‰. Our results suggest that early development of osmoregulatory ability, and thus of salinity tolerance in sea bass, may provide an advantageous flexibility for the timing of migration towards low-salinity habitats. Received: 22 May 2000 / Accepted: 18 December 2000     

Fly ash content and distribution in lake sediments around a large power station: inferences from magnetic susceptibility analysis

The bulk magnetic susceptibility of sediments from artificial and natural lakes around a large coal-fired power station in NE Spain has been measured. Higher magnetic susceptibility values are found in lake sediments located SE of the power station. This distribution of susceptibility values is compatible with environmental and meterological studies of emissions from the power station, which indicate a dominant SE plume direction. Mineralogical studies, by means of X-ray diffraction and scanning electron microscopy, show that the highest susceptibility values found in the sediments are caused by magnetic iron spinels in the fly ash that is transferred to the environment by the power station particulate emissions. After the quantitative mineralogical studies of fly ash, two different methods of fly ash content determination in the sediments have been devised, showing very similar results. The low background magnetic susceptibility of the sediments in the study area and the high susceptibility resulting from the input of magnetic fly ash particles allows both delimitation of the polluted area around the power station, and quantification of the fly ash input into the natural sediments.     

Colonization of meiobenthos in oil-contaminated subtidal sands in the lower Chesapeake Bay

In-situ manipulative experiments were conducted over a 3-month period (May–August 1980) to examine the rate at which meiobenthos colonizes oiled and untreated azoic fine sands at a shallow subtidal site in the lower York River, Virginia. Three concentrations of fresh Prudhoe Bay crude oil were added to sediments: 100, 2 500 and 10000 mg oil kg^-1 dry wt sediment. Untreated azoic and natural sediments served as controls. Within 16 d, meiofauna densities in all treatments were comparable to natural populations in surface oxidized sediments, but densities fluctuated greatly during the remainder of the sampling period. Nematodes slowly colonized the subsurface anoxic sediments below the redox potential discontinuity (RPD); some less common species did not significantly recover below the RPD in the two more heavily oiled treatments. Analysis of nematode community composition by reciprocal averaging ordination and numerical classification revealed generally lower abundances, but no distinct differences, in species composition in the oiled substrates as compared to untreated and natural community controls. Ordination of sequential samples suggested that the nematode species assemblages in the untreated controls fully recovered from these small-scale disturbances by 90 d. Life history characteritics and frequent tidal transport combine to make estuarine meiobenthos highly resilient following disturbance. Contrary to prior recolonization studies, a successional sequence was found for the colonizing nematodes which may be analogous to models of macrobenthic colonization (e.g. McCall, 1975). The comesomatid nematode Sabatieria pulchra, which is frequently dominant in polluted sediments, colonized relatively late in the experiment. Consequently, stress resistance and resilience may not be as coincident in meiofauna as in macrofauna because of differences in factors affecting their dispersal.     

Loft features influence the processing of navigational information by pigeons

The present study evaluates the impact of lofts on the development of the navigational system of pigeons. A series of results obtained between 2000 and 2004 were analyzed. The H-loft was placed 10 m above the ground, with a ring format and seven windows all around it as well as three external aviaries that allowed birds to have a wide view of the outdoors and of the sky and knowledge of the wind dynamics. The L-loft was placed at ground level, with a single window transformed into an external aviary. The L-loft was protected from the wind by surrounding trees, reducing the ability of the pigeons to access the wind dynamics and also restricting their access to information regarding the outside area and the sky. In a preliminary analysis, we found the parameter of “vanishing time” to differ significantly between lofts in two of the five age classes. A thorough analysis of this parameter throughout the ontogenetic development of the birds demonstrated a pronounced improvement in the information-processing system with age, with adults vanishing quicker than younger birds, although an impairment of development occurred during the third month of age, perhaps due to a reorganization of the system. This result was obtained when the effect of lofts was considered in the different age classes. Results suggest that loft features are an important factor in the ability of the young pigeons to exploit navigational cues.     

Propagation of olfactory information within the honeybee hive

Transfer of information about food source characteristics within insect societies is essential to colony-foraging success. The food odor communicated within honeybee hives has been shown to be important for food source exploitation. When successful foragers return to the nest and transfer the collected nectar to hive mates through mouth-to-mouth contacts (trophallaxis), potential recruits receiving these samples learn the food odor by associative learning. The food then becomes rapidly distributed among colony members, which is mainly a consequence of the numerous trophallaxes between hive-mates of all ages during food processing. We tested whether the distribution of food among hive mates causes a propagation of olfactory information within the hive. Using the proboscis extension response paradigm, we show that large proportions of bees of the age groups representing the main worker castes, 4 to 9-day-old bees (nurse-aged bees), 12 to 16-day-old bees (food processor-aged bees), and actual foragers (about 17+ day old bees) associatively learn the food odor in the course of processing food that has been collected by only a few foragers. Results further suggest that the information is shared more or less equally between bees of the three age groups. This shows that olfactory information about the flower species exploited by foragers is distributed within the entire colony and is acquired by bees of all age groups, which may influence many behaviors inside and outside the hive.     

Industry Response to the Challenge of Sustainability: The Case of the Canadian Nonferrous Mining Sector

/ The paper investigates how the Canadian nonferrous sector is tackling the challenge of sustainable development. Although there is no consensus as to what sustainable development means in practice for management in the sector, at least three dimensions must be taken into account: (1) metals are recyclable, the availability of this resource is not a concern for the foreseeable future; (2) the need to minimize environmental impacts of metals exploration, extraction, transformation, consumption, and recycling; and (3) production activities should not be socially or culturally disruptive. The nonferrous mining industry faces several environmental problems. Some of the most significant are acid mine drainage, sulfur emissions, recycling, and metals toxicity. The industry has developed a number of responses to address these specific concerns as well as other more general challenges. Six strategies are described and analyzed: (1) research and development, (2) an effort of consensus building among stakeholders known as the Whitehorse Mining Initiative, (3) international networking, (4) active involvement in the development of environmental management standards, (5) management reorganization and (6) voluntary agreements. The importance of external factors in the shaping of corporate environmental management practices is discussed, in particular the role of government. Progress has been achieved in three areas: (1) managerial practices and organization, (2) reducing the impacts of ongoing operations and (3) minimizing future liabilities, but two significant fields of conflict remain, namely mining in wilderness areas and projects on aboriginal lands.KEY WORDS: Canada; Environmental management; Minerals industry; Nonferrous metals; Sustainable development; Whitehorse Mining Initiative     

Fluid flow and solute transport in a network of channels

A new model to describe flow and transort in fractured rocks is proposed. It is based on the concept of a network of channels. The individual channel members are given stochastically selected conductances and volumes. Flow-rate calculations have been performed. For large standard deviations in conductances, channeling becomes pronounced with most of the water flowing in a few paths. The effluent patterns and flow-rate distributions obtained in the simulations have been compared to three field measurements in drifts and tunnels of flow-rate distributions. Standard deviations of channel conductances were between 1.6 and 2.4 in some cases. A particle-following technique was used to simulate solute transport in the network. Non-sorbing as well as sorbing solute transport can be simulated. By using a special technique, solutes that diffuse into the rock matrix can also be simulated.