Exposure to DDT and HCH congeners and associated potential health risks through khat (Catha edulis) consumption among adults in South Wollo,Ethiopia

Environmental Geochemistry and Health - Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public...     

Melanin-based colour polymorphism signals aggressive personality in nest and territory defence in the tawny owl (Strix aluco)

Nest and territory defence are risky and potentially dangerous behaviours. If the resolution of life history trade-offs differs between individuals, the level of defence may also vary among individuals. Because melanin-based colour traits can be associated with life history strategies, differently coloured individuals may display different nest and territory defence strategies. We investigated this issue in the colour polymorphic tawny owl (Strix aluco) for which plumage varies from dark to light reddish melanic. Accordingly, we found that (1) our presence induced a greater response (flying around) from dark-coloured than light-coloured females and (2) dark reddish males suffered lower nest predation rates than light-coloured males. In experimentally enlarged broods, the probability that females reacted after we played back the hoot calls of a stranger male was higher if these females were lighter reddish; the opposite pattern was found in experimentally reduced broods with dark parents being more reactive than light parents. Finally, darker females alarmed more frequently when paired with a light than with a dark male, suggesting that partners adjust their behaviour to each other. We also tested whether colouration is used as a signal by conspecifics to adjust the level of their defensive behaviour. Accordingly, breeding females responded more vigorously to a dark than a light reddish stuffed tawny owl placed beside their nest. We conclude that melanin-based colouration is a signal of alternative nest and territory defence behaviour that depends on ecological factors.     

Habitat fragmentation affects movement behavior of migrating juvenile common toads

Displacement characteristics in animals are crucial drivers of successful movement decisions in resources acquisition, migration, and dispersal. As landscape structure is modified by human activity, mobility patterns are likely to evolve in response to habitat fragmentation. In species with complex life cycles that involve obligatory migrations between different habitats, one can predict that movement propensity would be promoted by fragmentation as long as it allows to reaching a habitat patch. Here, we compare the movement characteristics of naive toadlets sampled in populations distributed over a fragmentation gradient to test the hypothesis of a positive correlation between fragmentation and mobility levels. We studied toadlet movement in experimental arenas providing small patches of suitable conditions. We recorded the use of these patches (patch behavior) or the absence of their use (overtaking behavior). The more fragmented the original landscape, the more prone the toadlets were to combine these two behaviors, thus showing a higher motivation to explore. Moreover, the more fragmented the original landscape, the less the toadlets exhibited patch behavior. As the toadlets were reared in a common environment, the behavioral differences detected, relating to the level of fragmentation, resulted from inheritance. Our results thus illustrate that fragmentation is likely to create cross-generational transmittable variations in movement characteristics.     

Tissue,ontogenic and sex-related differences in δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N values of the oceanic squid <Emphasis Type="Italic">Todarodes filippovae</Emphasis> (Cephalopoda: Ommastrephidae)

Stable isotopes are increasingly used in the study of trophic interactions of many aquatic animals and most recently cephalopods. To evaluate the application of the method to squids, it is important to assess isotopic differences among and within consumer tissues that may confound the resolution of ecological relationships. Inter- and intra-tissue isotopic variation was examined in 55 individuals of the oceanic squid Todarodes filippovae that were collected at the beginning of April 2000 in the southwestern Indian Ocean (between 44°S, 76°E, and Saint Paul and Amsterdam islands, 38°S, 78°E). Delipidated soft tissues (mantle, arm, buccal mass, gill and reproductive organs) showed small δ¹³C and δ¹⁵N differences, which were probably tissue-specific. A lower carbon value was observed in the digestive gland as a consequence of incomplete lipid removal. Hard tissues, such as beaks and gladii, had lower ¹⁵N values than soft tissues, which can be explained by the presence of chitin, a ¹⁵N-depleted molecule. Females (n = 38) and males (n = 17) had identical δ¹³C values, but females showed higher δ¹⁵N values than males. The difference was size-related rather than sex-related, however, as females were generally larger than males. A comparison of similar-sized females and males produced identical nitrogen values. These data suggest dietary shifts from lower to higher trophic levels during growth, because δ¹⁵N values of large T. filippovae were much higher than that of small specimens. As expected, nitrogen values of lower beaks and gladii of large squids increased from the oldest to the most recently formed region, reflecting the progressive growth of chitinized tissues in parallel with dietary changes. Sequential sampling along the growth increments of squid beaks and gladii can likely be used to produce a chronological record of dietary information throughout an individual’s history.     

Response of tree growth to a changing climate in boreal central Canada: A comparison of empirical,process-based,and hybrid modelling approaches

The impact of 2 × CO₂ driven climate change on radial growth of boreal tree species Pinus banksiana Lamb., Populus tremuloides Michx. and Picea mariana (Mill.) BSP growing in the Duck Mountain Provincial Forest of Manitoba (DMPF), Canada, is simulated using empirical and process-based model approaches. First, empirical relationships between growth and climate are developed. Stepwise multiple-regression models are conducted between tree-ring growth increments (TRGI) and monthly drought, precipitation and temperature series. Predictive skills are tested using a calibration–verification scheme. The established relationships are then transferred to climates driven by 1× and 2 × CO₂ scenarios using outputs from the Canadian second-generation coupled global climate model. Second, empirical results are contrasted with process-based projections of net primary productivity allocated to stem development (NPP_s). At the finest scale, a leaf-level model of photosynthesis is used to simulate canopy properties per species and their interaction with the variability in radiation, temperature and vapour pressure deficit. Then, a top-down plot-level model of forest productivity is used to simulate landscape-level productivity by capturing the between-stand variability in forest cover. Results show that the predicted TRGI from the empirical models account for up to 56.3% of the variance in the observed TRGI over the period 1912–1999. Under a 2 × CO₂ scenario, the predicted impact of climate change is a radial growth decline for all three species under study. However, projections obtained from the process-based model suggest that an increasing growing season length in a changing climate could counteract and potentially overwhelm the negative influence of increased drought stress. The divergence between TRGI and NPP_s simulations likely resulted, among others, from assumptions about soil water holding capacity and from calibration of variables affecting gross primary productivity. An attempt was therefore made to bridge the gap between the two modelling approaches by using physiological variables as TRGI predictors. Results obtained in this manner are similar to those obtained using climate variables, and suggest that the positive effect of increasing growing season length would be counteracted by increasing summer temperatures. Notwithstanding uncertainties in these simulations (CO₂ fertilization effect, feedback from disturbance regimes, phenology of species, and uncertainties in future CO₂ emissions), a decrease in forest productivity with climate change should be considered as a plausible scenario in sustainable forest management planning of the DMPF.     

Factors affecting information transfer from knowledgeable to naive individuals in groups

There is evidence that individuals in animal groups benefit from the presence of knowledgeable group members in different ways. Experiments and computer simulations have shown that a few individuals within a group can lead others, for a precise task and at a specific moment. As a group travels, different individuals possessing a particular knowledge may act as temporary leaders, so that the group will, as a whole, follow their behaviour. In this paper, we use a model to study different factors influencing group response to temporary leadership. The model is based on four individual behaviours. Three of those, attraction, repulsion, and alignment, are shared by all individuals. The last one, attraction toward the source of a stimulus, concerns only a fraction of the group members. We explore the influence of group size, proportion of stimulated individuals, number of influential neighbours, and intensity of the attraction to the source of the stimulus, on the proportion of the group reaching this source. Special attention is given to the simulation of large group size, close to those observed in nature. Groups of 100, 400 and 900 individuals are currently simulated, and up to 8,000 in one experiment. We show that more stimulated individuals and a larger group size both induce the arrival of a larger fraction of the group. The number of influential neighbours and the intensity of the stimulus have a non-linear influence on the proportion of the group arrival, displaying first a positive relationship and then, above a given threshold, a negative one. We conclude that an intermediate level of group cohesion provides optimal transfer information from knowledgeable to naive individuals.     

Interspecific and geographical variations of trace element concentrations in Pectinidae from European waters

Cd, Cu and Zn were analysed in the organs and tissues of the three scallop species from the Bay of Biscay, the variegated Chlamys varia L., the queen scallop Aequipecten opercularis L. and the common scallop Pecten maximus L. for interspecific comparisons. In P. maximus the greatest concentrations of Cd and Cu were found in the digestive gland, whereas the two other species showed similar levels of Cd between digestive gland and kidneys and higher renal Cu concentrations. However, the digestive gland of all Pectinidae species contained from 75% to 93% and 52% to 74% of the total body burdens of Cd and Cu, respectively. Whatever the species, kidneys displayed the highest Zn concentrations, which therefore contained from 53% to 97% of the total body burden of this metal. Also using reported results, ratios between the concentrations in the digestive gland and that in the kidneys discriminated two groups of Pectinidae: (1) the Pecten group (P. maximus, P. jacobeus and Adamussium colbecki) with a Cd ratio > or = 4, a Cu ratio > or = 1 and a Zn ratio > 20x10(-3); (2) the Chlamys group with a Cd ratio < or = 1, a Cu ratio < or = 1 and a Zn ratio < or = 6x10(-3). However, no differences in the detoxification processes in the digestive gland were found between groups in this study. 72-80% of the total Cd was found to be soluble, probably bound to metalloproteins such as metallothioneins, while Cu and Zn were mainly found associated to the insoluble fraction of the digestive gland cells whatever the species. Queen scallops from the Faroe Islands were also considered to examine variations of the metal concentrations due to the geographical origin. In this northern area, queen scallops displayed Cd concentrations 2, 4 and 6 times higher in kidneys, muscle and digestive gland, respectively, compared to those from the Bay of Biscay. Consequently, the Cd concentrations in the whole soft parts of the queen scallops were more than 6 times higher in the Faroe Islands than in the Bay of Biscay. In contrast to Cd, both Cu and Zn concentrations in the whole soft parts were 2 times lower in the Faroe Islands, suggesting lower bioavailability of these essential elements.     

Radiocarbon behaviour in seawater and the brown algae Fucus serratus in the vicinity of the COGEMA La Hague spent fuel reprocessing plant (Goury)--France

Extensive studies of the radiocarbon (14C) distribution and transfer in the marine environment of the North-Cotentin peninsula and along the English Channel have been carried out. The main aims of these studies have been to estimate the spatial and temporal variation of the 14C concentration in seawater and to calculate 14C concentration factors for some biological species. Such information will be helpful in order to calculate precisely radiation doses to humans. First results obtained in the vicinity of the COGEMA La Hague nuclear plant (Goury) indicate a 14C labelling of the dissolved inorganic carbon (DIC) in seawater (8.0-26.2 Bq.m(-3)) and a tight relationship between the 14C in the liquid releases from the plant and the 14C concentrations in DIC. The particulate organic carbon (POC) is also labelled. The concentration factor calculations for the brown algae (Fucus serratus) sampled from Goury, and also along the English Channel, give 14C values around 3000 Bq.kg(-1) fresh weight / Bq.L(-1).     

Mussel transplantation and biomarkers as useful tools for assessing water quality in the NW Mediterranean

Mussels, coming from an aquaculture farm located in a clean open bay, were transplanted to several stations of the bays of Nice and Cannes (NW Mediterranean) including a reference site for one month at three periods. Several biomarkers: activities of glutathione S-transferase (GST; exposure to organics), of catalase (exposure to oxidative stress) and of acetylcholinesterase (inhibited by some pesticides) and the lipid peroxidation (thiobarbituric acid reactive substances: TBARS) were measured in transplanted mussels. Cd, Cu and Zn concentrations were also measured as well as their condition index. The results demonstrated some seasonal variations in GST and catalase activities with higher levels in June compared to October. The condition index was also higher in June than in October. Principal component analyses performed with the whole set of data allowed to separate stations or groups of stations according to their responses. The mussels from the harbour of Nice were characterized by high TBARS levels and catalase activity in October 1999 whereas in the harbour of Cannes, animals presented very high copper concentrations and GST activities in June 2000. At the reference site, mussels generally presented low enzymatic activities (except AChE activity) and peroxidation levels and low heavy metal concentrations.