Short-distance dispersal of Hypothenemus hampei (Ferrari) females (Coleoptera: Curculionidae: Scolytidae) during the coffee tree fruiting period.

The coffee berry borer (CBB), Hypothenemus hampei (Ferrari), is a multivoltine species closely associated with coffee crops worldwide, causing severe damage to the bean. In Mexico, as in all tropical regions, CBB survives during the inter-harvest period in residual berries on the ground or in dry berries remaining on the branches, and then disperses in search of the first suitable berries. In this study, we investigated how CBB dispersed from the first infested nodes during the fruiting period of Coffea canephora Pierre, which provides a favourable trophic level for this insect. Forty-five branches equally distributed in 15 coffee trees, with one infested node and four uninfested nodes, were selected. The branches were subjected to three treatments over nine weeks: 1) glue between nodes with full protection, 2) glue between nodes without protection, and 3) no glue and no protection. In addition, 45 CBB-free branches were selected and subjected to the same three treatments. CBB colonization can occur in three ways: 1) from an infested node to an uninfested node on the same branch, 2) from infested berries to uninfested berries within the nodes, 3) from branches to other branches. We also found that CBB dispersal between nodes of the same branches never occurred by walking but by flying. Thus, in this context of coffee berry development and ripening, and unlike the phenological situation of the inter-harvest period, CBB continuously travels very short distances, thus limiting its control.

Climatic factors directly impact the volatile organic compound fingerprint in green Arabica coffee bean as well as coffee beverage quality.

Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC-MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality.

Fine-scale tissue distribution of cadmium, inorganic mercury, and methylmercury in nymphs of the burrowing mayfly Hexagenia rigida studied by whole-body autoradiography.

The distribution of inorganic 109Cd(II), inorganic 203Hg(II), and [203Hg] methylmercury (MeHg) in nymphs of the burrowing mayfly Hexagenia rigida after exposure via water and sediments was studied. To better understand the mechanisms underlying the fate of Cd, Hg, and MeHg in this animal and to identify target organs, autoradiography of whole-body cryosections was used to obtain a detailed view of the distribution of the radiolabels. The gut and exoskeleton were the only structures labeled in nymphs exposed to Cd via water or sediments. After exposure to inorganic Hg via water, the Malpighian tubules exhibited a very high labeling, indicating that these organs may be a target for Hg toxicity. The distribution of Hg after exposure via sediments was similar, though the labeling of Malpighian tubules was less intense. Distribution of MeHg strongly differed between treatment groups. Nymphs were rather uniformly labeled after exposure via water, whereas in those exposed to MeHg in sediments, the intense labeling of all internal tissues contrasted with the very low labeling of the hemolymph, indicating that the translocation rate of the absorbed MeHg was faster in the latter group. This may be related to the complexation of MeHg by small thiol ligands in the gut as a result of the digestion process.

Interspecific comparison of cadmium and zinc contamination in the organs of four fish species along a polymetallic pollution gradient (Lot River, France).

The impact of cadmium (Cd) and zinc (Zn) discharges related to an old zinc ore treatment facility in the Lot River (France) was investigated in four fish species (the chub: Leusciscus cephalus, the roach: Rutilus rutilus, the perch: Perca fluviatilis and the bream: Abramis brama). The organisms were sampled in four stations along the polymetallic contamination gradient. Cd and Zn analysis were carried out in five organs (gills, posterior intestine, liver, kidneys and skeletal muscle) in order to highlight the potential pathways of uptake, storage and elimination of metals. The results indicate a very strong Cd contamination in fish collected downstream from the metal source. The kidneys have the highest cadmium concentrations, but the gills and the intestine, as exchange organs, present the largest variations between the stations in close relation with the contamination gradient. Cd concentrations measured in the liver vary only slightly among the sampling stations. Unlike the trends observed for Cd, Zn levels in fish populations are strongly regulated and do not follow ambient Zn concentrations. The concentrations measured vary also according to fish species, for both Cd and Zn. This study shows that the trophic habits can explain the interspecific differences in Cd bioaccumulation. Zn levels observed for each species in non-contaminated populations also help to understand metal bioaccumulation patterns in polluted sites, suggesting that the determinism of interspecific differences is constitutive.

Comparative experimental study of cadmium and methylmercury trophic transfers between the asiatic clam Corbicula fluminea and the crayfish Astacus astacus.

Cadmium (Cd) and methylmercury (MeHg) trophic transfers were analyzed between the Asiatic clam Corbicula fluminea and the crayfish Astacus astacus. Metal bioaccumulation in crayfish was quantified after 5, 10, and 15 days of exposure via daily ingestion of soft bodies of C. fluminea, previously exposed during 7 days to Cd (20 microg. L(-1)) and MeHg (4 microg. L(-1)). Bioaccumulation kinetics in the predator were investigated at organ and tissue levels: hemolymph, tail muscle, hepatopancreas, gills, stomach/mesenteron, intestine, green gland, carapace. Trophic transfer rates were estimated at the whole organism level. Results showed marked differences (1) in assimilation efficiencies, mean transfer rates being 5% for Cd and 16% for MeHg; and (2) in the metal distribution within the different tissue compartments of the crayfish: for Cd, the trophic uptake leads to high concentrations in the hepatopancreas and small accumulation in the muscle tissue; for MeHg, the highest levels of bioaccumulation occur in the green gland and in the tail muscle. From an ecotoxicological point of view, these experimental data suggest a small risk of Cd transfer between the crayfish and predators, humans included; on the other hand, Hg distribution in the muscle and accumulation trends in this tissue represent an obvious risk of transfer.

Effects of Temperature and Exposure Duration on Transfer of Cadmium Between Naturally Contaminated Sediments and Burrowing Mayfly Nymphs (Hexagenia rigida)

Burrowing mayfly nymphs (Hexagenia rigida) were exposed to naturally contaminated sediments collected from two stations along a metallic pollution gradient on the Lot River (France) using indoor microcosms. Bioaccumulation kinetics (0, 20, 40, and 60 days) of cadmium (Cd) and the combined effects of temperature (12, 18, and 24 degreesC) were evaluated by a complete experimental design, jointly with the analysis of growth rate of the nymphs, bioturbation, and total and dissolved Cd concentrations in the water column. Cadmium was transferred from the sediment to the organisms with uptake influenced by contamination levels of the sediments, exposure duration, and temperature. The two complementary criteria-Cd concentration and burden in the nymphs-clearly demonstrate the importance of the growth dilution on the quantification of Cd bioaccumulation at the whole organism level.

Role of temperature on isoproturon bioaccumulation and effects on two freshwater rooted macrophytes: Elodea densa and Ludwigia natans.

The effects of temperature on the bioaccumulation of the phenylurea herbicide isoproturon (IPU) and on the growth inhibition induced on two freshwater rooted macrophytes--Elodea densa and Ludwigia natans--were investigated using indoor microcosms. The experimental protocol was based on five temperatures (12, 16, 20, 24, and 28 degrees C) and two contamination levels of the water column (30 and 60 micrograms IPU.liter-1), plus a control condition. Variations in temperature had little effect on the decrease in [IPU] in the water column during the 21-day experiment. The IPU concentration in the two macrophyte species was not significantly modified by the large range of temperatures when results were expressed using the concentration criterion. IPU burdens in the E. densa cuttings, on the other hand, increased significantly when the temperature rose from 12 to 28 degrees C; small differences were observed between the two exposure conditions, in relation to the antagonistic effects of IPU and temperature on the growth of the cuttings. Bioconcentration factors in the plants (stems + leaves) were close to 10 and 13 after exposure to 30 and 60 micrograms IPU.liter-1, respectively.

Aquatic ecotoxicology: from the ecosystem to the cellular and molecular levels.

This review of aquatic ecotoxicology is presented in three parts. First, we discuss the fundamental concepts and stress the importance of its ecological basis and the complexity and diversity of the field of investigation, which result from actions and interactions between the physicochemical characteristics of the biotopes, the structural and functional properties of the living organisms, and the contamination modalities. Ecotoxicological mechanisms, regardless of the level of biological complexity, primarily depend on the bioavailability of the toxic products. Numerous processes control the chemical fate of contaminants in the water column and/or sediment compartments; accessibility to the biological barriers that separate the organisms from their surrounding medium depends directly on bioavailability. Second, we review the principal methodologies of the field, from in situ studies at the ecosystem/ecocomplex level to bioassays or single species tests. Third, we focus on mercury, selected as a reference contaminant, in order to illustrate the main ecotoxicological concepts, the complementarity between field and laboratory studies, and the indispensable multidisciplinarity of the approaches.

Tissue distribution of inorganic mercury, methylmercury and cadmium in the Asiatic clam (Corbicula fluminea) in relation to the contamination levels of the water column and sediment.

The comparative experimental study of inorganic mercury (HgII), methylmercury (MeHg) and cadmium (Cd) bioaccumulation in the Asiatic clam Corbicula fluminea was based on a 14 days' exposure to the water column or sediment compartments, as initial contamination sources. For each contaminant and exposure source, a five-point concentration range was set up in order to quantify the relationships between the contamination pressure and bioaccumulation capacity, at the whole soft body level and in five organs: gills, mantle, visceral mass, kidney and foot. Hg and Cd bioaccumulation at the whole organism level was proportional to the metal concentrations in the water column or sediment. For similar exposure conditions, the average ratios between the metal concentrations in the bivalves--[MeHg]/[HgII] and [MeHg]/[Cd]--were close to 10 and 5 for the sediment source and 8 and 15 for the water column source. Metal distribution in the five organs revealed strong specificities, according to the different contamination modalities studied: kidney and gills were clearly associated with Cd exposure, mantle and foot with MeHg exposure and the visceral mass with inorganic Hg exposure.

Effects of the phenylurea herbicide isoproturon on periphytic diatom communities in freshwater indoor microcosms.

The toxic effects of the phenylurea herbicide Isoproturon -IPU: (3-(4-isopropylphenyl)-1, 1-dimethylurea)-were studied on the colonization of periphytic diatom communities, within indoor microcosms consisting of a mixed biotope (water column and natural sediment) and two biological species-rooted macrophyte cuttings (Elodea densa) and benthic bivalve molluscs (Corbicula fluminea). The periphyton, essentially composed of diatoms, was collected on artificial substrata (glass slides) in the upper layers of the water column, after two periods of exposure (34 and 71 days). IPU was initially added in the water or in the sediment compartment, at two nominal concentrations (L1 and L2 levels) for each contamination source-5 and 20 microg litre(-1) and 100 and 400 microg kg(-1) in sediment (w/w) respectively. The effects of IPU on the density and community structure of periphytic diatoms are described. A marked reduction in the diatom density was observed after 34 days exposure to the lower concentration of IPU in the water (5 microg litre(-1)). For the L2 levels, the very small number of live cells present did not permit quantification of the diatom density. After 71 days, recovery in community parameters occurred for the two contamination levels of the sediment and water column sources. Samples collected in the experimental units contaminated with the L2 levels were dominated by heterotrophic and smaller diatom species, such as Sellaphora seminulum. Data treatment based on factorial discriminant analysis enabled us to distinguish the different contamination conditions, with only 11 species from the 130 taxa identified.

Herbicide isoproturon-specific binding in the freshwater macrophyte Elodea densa--a single-cell fluorescence study.

The experimental approach to the effects of the phenylurea herbicide Isoproturon (IPU), on the photosynthesis activity of leaf cells of the freshwater macrophyte Elodea densa was based on the fast induction kinetics of the PSII chlorophyll a in vivo fluorescence. FI/FP ratios determined on the induction curves exhibited a noticeable effect at 5 micrograms IPU.liter-1. They appeared to be the most reliable parameter for the quantitative evaluation of the dissociation constant of the complex "IPU/D1 protein" (Kd = 1.2 x 10(-7) M) and of the concentration of free IPU either at the thylakoid level or in the surrounding medium of the leaf epithelial cells. Total IPU bioaccumulation at the whole plant level as a function of [IPU] in the medium indicated that the D1 protein represented the main binding site for IPU in this aquatic plant species.

Experimental study of interactions between five trace elements--Cu, Ag, Se, Zn, and Hg--toward their bioaccumulation by fish (Brachydanio rerio) from the direct route.

Actions and interactions between five elements--copper, zinc, silver, selenium, and methyl mercury--toward their bioaccumulation in fish (Brachydanio rerio) were studied after 12 days exposure, via the direct contamination route. The experimental approach was based on a centered composite factorial design; 43 different contamination conditions were studied simultaneously, with five concentration levels in the water for each element. Contaminated media were cyclically renewed (48 hr renewal cycle), in order to control the fish exposure conditions. Data treatment was essentially based on the multiple regression technique, applied successively to the complete factorial design (2(5) = 32 conditions) and to the centered composite design (43 conditions). Results show a complex set of actions and interactions between the elements. The most striking result is a marked interaction between silver and methyl mercury: when Ag is present in the water jointly with MeHg, it exerts a negative action on Hg bioaccumulation in the fish, at the whole organism level. Bioaccumulation of silver is also significantly influenced by the presence of Zn, Cu, and Se in the water, the action of these three elements producing an increase in the amounts of Ag in the organisms. This study corresponds to an exploratory phase in order to reveal interaction effects on the bioaccumulation processes by fish and then to set up more in-depth analysis to increase progressively the understanding of the ecotoxicological mechanisms involved.

Cadmium and methylmercury bioaccumulation by nymphs of the burrowing mayflyHexagenia rigida from the water column and sediment.

Based on a three compartment microcosm-water column, natural sediment,Hexagenia rigida nymphs-an experimental study was set up to compare cadmium (Cd) and methylmercury (MeHg) bioaccumulation by a burrowing mayfly species, after exposure via the water column or the sediment as initial contamination sources. Results from a wide concentration range for each exposure condition revealed very marked differences between the two metals: MeHg was readily accumulated from the two contamination sources, leading to important metal concentrations in the nymphs after the 2 weeks' exposure; Cd bioaccumulation, on the other hand, was negligible when the metal was added to the water compartment, even though significant transfers were observed from the sediment source. The average Cd concentrations in the nymphs were proportional to the sediment contamination levels. Turbidity measurements in the water column, reflecting the bioturbation activity of the nymphs, revealed that the effect of Cd was significant, but only when the metal was initially added to the sediment. The results are discussed according to the uptake routes and the structural and functional properties of the biological barriers involved (gills and gut).

Experimental study of inorganic and methylmercury bioaccumulation by four species of freshwater rooted macrophytes from water and sediment contamination sources.

An experimental study based on four species of rooted macrophytes (Elodea densa, Ludwigia natans, Lysimachia nummularia, Hygrophila onogaria) was carried out to quantify and compare their mercury bioaccumulation capacity from the water column and the sediment compartments as initial sources of contamination. The first stage consisted of analyzing plant growth (weight and total length) in relation to six different characteristics of the biotopes, resulting from the combination of three types of sediment (natural sediment, sediment+sand, clay) and two types of aquatic medium (synthetic river water, dechlorinated tap water). This preliminary experiment permitted selection of the basic structure of the experimental units--a mixed biotope consisting of dechlorinated tap water and a mixture of natural sediment+sand--for the comparative analysis of mercury bioaccumulation capacities. In the second stage, two chemical forms of mercury were considered (HgCl2 and CH3HgCl), the metal being introduced into the sediment at the beginning of the experiment ("sediment" source) or into the water column by twice-daily additions ("water" source). Results showed very great accumulation differences after 18 or 21 days exposure: (a) Hg concentrations in the plants (stems+leaves) were always greater when the metal was introduced in organic form, with even greater differences when initial contamination was via the sediment; (b) according to the selected experimental conditions, mercury bioaccumulation by the macrophytes from the water source was about 10 times greater than that observed when the metal was introduced into the sediment, and thus, despite the strong differences between the contamination levels of these two sources, in favor of the sediment (factor close to 10(3) for the two compounds); and (c) major interspecies differences emerged in Hg burdens accumulated by the plants, with differences being very small when results were expressed as concentrations, thus taking account of the different biomasses of the species.

Comparative study of mercury accumulation in dolphins (Stenella coeruleoalba) from French Atlantic and Mediterranean coasts.

Total mercury concentrations (Hgt) have been determined in liver, kidneys, skeletal muscle, melon, stomach and intestine of 35 specimens of Stenella coeruleoalba stranded on French Atlantic and Mediterranean coasts. Very high mercury levels, with concentrations reaching 80 mg Hgt kg(-1) fresh weight (FW) in muscle and about 1500 mg Hgt kg(-1) FW in liver tissue, were observed. Liver has the highest concentration, followed by muscle and kidney. The lowest concentrations were found in the melon. The levels observed in the Mediterranean specimens are among the highest observed in marine organisms and confirm previous reports of high mercury levels in marine mammals from the Mediterranean. Comparison between Hgt accumulation levels in these two geographic groups of dolphins shows that Mediterranean individuals have much higher concentrations than specimens from the Atlantic. These differences provide additional confirmation for the higher Hgt concentrations observed previously in other pelagic species (tuna, sardine, anchovy, etc.) from the Mediterranean Sea. Taking into consideration the pelagic habitat of the dolphin and the local influence of anthropogenic mercury sources it seems reasonable to assume that the main source of the high mercury concentrations observed in Mediterranean biota is natural mercury deposits located in many regions of the Mediterranean basin.

Hexagenia rigida (ephemeroptera) as a biological model in aquatic ecotoxicology: experimental studies on mercury transfers from sediment.

The accumulation of two mercury compounds--HgCl(2) and CH(3)HgCl--by Hexagenia rigida (burrowing mayfly nymphs) from contaminated sediments was investigated experimentally. Three exposure periods were selected: 7, 14 and 28 days. Results reveal a high capacity of this species for Hg accumulation and considerable differences between the two chemical forms of the metal. Thus, the amount of total mercury accumulated after 28 days' exposure would be 60 times greater for the organic form if the two compounds were initially added to the sediment in the same concentrations. No significant growth inhibition appears for the different experimental conditions studied. Data treatment at the organism level showed a positive linear correlation between the fresh weight and Hg content in the nymphs; this was especially marked when the exposure time was relatively long and Hg was in the form of CH(3)HgCl. The study of mercury distribution in the organs of Hexagenia rigida (gills and gut) and the examination of results obtained in similar experimental conditions after contamination of the nymphs via the water column showed the importance of the trophic route, via ingested sediment, for the bioaccumulation of the metal initially introduced into the sediment.

Structural and ultrastructural analysis of gills and gut of Hexagenia rigida nymphs (ephemeroptera) in relation to contamination mechanisms.

In the context of an experimental approach to organic and inorganic mercury bio-accumulation by burrowing mayfly nymphs-Hexagenia rigida-, gills and different parts of the gut were investigated by light and electron microscopes. In the gut, two regions were studied: (1) mesenteron (midgut) characterized by cells with microvilli and a peritrophic membrane throughout this part, a lot of fungal hyphae being found on it; (2) proctodeum (hindgut) characterized by macrovilli, the apical face of cells being covered by a thick layer of chitin; many bacteria were observed at the bottom of macrovilli. The stomodeum (foregut) is extremely short. The gills are made up of six pairs of lamellae fringed with long filaments which are arranged on both sides of the long axis. Gills are constituted by tracheae and tracheoles, with a large canal for haemolymph circulation; muscle masses and nerve bundles were also observed. This structural approach shows that the nymph interface with the external environment, at gill and gut barrier levels, are quite different. Links between this structural and ultrastructural analysis and contamination mechanisms, via the trophic or direct route, are discussed; gills and gut could be transfer routes for mercury absorption, but also target organs for metal accumulation.

Cadmium contamination of tissues and organs of delphinids species (Stenella attenuata)--influence of biological and ecological factors.

Based on a sample of 27 dolphins (Stenella attenuata) captured in the Eastern tropical zone of the Pacific Ocean, this study was carried out to analyze the cadmium accumulation levels and distribution in 12 organs or tissue samples. The average cadmium concentrations were between 0.2 mg Cd.kg-1 in the brain and muscle and 48 mg Cd.kg-1 in the kidneys. For most of organs and tissues the average values were between 1 and 5 mg Cd.kg-1. Kidneys, liver, muscle, and intestine contained almost 85% of the total cadmium burden of all tissues considered in this study. Most of the biological and ecological factors taken into account (age, sex, total weight, and length of the dolphins, weight of the organs, place and date of capture) interacted with the cadmium concentrations and burdens in the collected organs or tissues. Three factors appear to be of prime importance: age, body weight, and geographical location of the area of capture.