Health importance of arsenic in drinking water and food

Arsenic is a toxic metalloid of global concern. It usually originates geogenically but can be intensified by human activities such as applications of pesticides and wood preservatives, mining and smelting operations, and coal combustion. Arsenic-contaminated food is a widespread problem worldwide. Data derived from population-based studies, clinical case series, and case reports relating to ingestion of inorganic arsenic in drinking water, medications, or contaminated food or beverages show the capacity of arsenate and arsenite to adversely affect multiple organ systems. Chronic arsenic poisoning can cause serious health effects including cancers, melanosis (hyperpigmentation or dark spots, and hypopigmentation or white spots), hyperkeratosis (hardened skin), restrictive lung disease, peripheral vascular disease (blackfoot disease), gangrene, diabetes mellitus, hypertension, and ischemic heart disease.     

Use of heterospecific cues by the lizard Platysaurus broadleyi for food location

Flat lizards (Platysaurus broadleyi) at Augrabies Falls National Park, South Africa, are restricted to rocky terrain where the predominant tree is the Namaqua fig (Ficus cordata cordata). P. broadleyi readily feeds on Namaqua figs when they are available, and the lizards sometimes form large (maximum recorded=134) congregations under fruiting fig trees. The distance lizards travel to fruiting trees also exceed normal daily foraging distances. Location of fruiting fig trees by a lizard can have a high pay-off because figs are energetically rich and trees fruit irregularly and asynchronously, resulting in a resource that is available, but unpredictable in time and space. The prediction that bird activity in fig trees provides a cue to the presence of ripe figs was tested experimentally. By placing cages containing birds and empty control cages in trees devoid of fruit, we demonstrated that P. broadleyi are drawn to fig trees with high bird congregations. We also tested if the presence of a fig tree was necessary to draw lizards to bird congregations by placing cages containing birds and empty control cages in a matched-pairs design on rock away from trees. Namaqua fig trees were not necessary to draw lizards to bird congregations. Received: 12 May 1998 / Accepted after revision: 30 November 1998     

Evidence supporting the importance of terrestrial carbon in a large-river food web

Algal carbon has been increasingly recognized as the primary carbon source supporting large-river food webs; however, many of the studies that support this contention have focused on lotic main channels during low-flow periods. The flow variability and habitat-heterogeneity characteristic of these systems has the potential to significantly influence food web structure and must be integrated into models of large-river webs. We used stable-isotope analysis and IsoSource software to model terrestrial and algal sources of organic carbon supporting consumer taxa in the main channel and oxbow lakes of the Brazos River, Texas, USA, during a period of frequent hydrologic connectivity between these habitat types. Standardized sampling was conducted monthly to collect production sources and consumer species used in isotopic analysis. Predictability of hydrologic connections between habitat types was based on the previous 30 years of flow data. IsoSource mixing models identified terrestrial C3 macrophytes (riparian origin) as the primary carbon source supporting virtually all consumers in the main channel and most consumers in oxbow lakes. Small-bodied consumers (<100 mm) in oxbow lakes assimilated large fractions of algal carbon whereas this pattern was not apparent in the main channel. Estimates of detritivore trophic positions based on delta15N values indicated that terrestrial material was likely assimilated via invertebrates rather than directly from detritus. High flows in the river channel influenced algal standing stock, and differences in the importance of terrestrial and algal production sources among consumers in channel vs. oxbow habitats were associated with patterns of flooding. The importance of terrestrial material contradicts the findings of recent studies of large-river food webs that have emphasized the importance of algal carbon and indicates that there can be significant spatial, temporal, and taxonomic variation in carbon sources supporting consumers in large rivers.     

The role of posturing and calling in the begging display of nestling birds

Nestling birds produce a multicomponent begging display that has visual (e.g. posturing) and vocal (e.g. call rate) elements. Most work on the function of the display has focused on each component separately. However, understanding the evolution of complex displays such as begging requires knowledge of how the components function collectively. The purpose of our study was to determine how postural intensity and calling rate together influence parental feeding decisions in tree swallows, Tachycineta bicolor. We compared how begging components responded to a manipulation in which pairs of nestlings were either free to approach the parent when it arrived to feed (unconfined treatment) or confined to the back of their nestbox by a Plexiglass partition (confined treatment). We found no significant differences in postural intensity between treatments, but calling rate was significantly higher in the confined treatment. In both treatments, postural intensity, but not calling rate, correlated with hunger. Both components positively and independently correlated with the likelihood of a nestling being fed, although the correlation with postural intensity was stronger. Previous work suggested that both posture and call rate advertised hunger in nestling tree swallows. Here, call rate was not associated with hunger, but rather was affected by nestling position. These results suggest that calling may serve an additional role in helping nestlings in disadvantaged positions attract parental attention. The results also suggest that calling may have a complex relationship with hunger, position and nestmates.     

The role of a scent beacon in the communication of food location by the stingless bee, Melipona panamica

Melipona panamica foragers can deposit a scent beacon that influences the orientation of foragers near a food source. In misdirection experiments, newcomers (bees from the same colony as trained foragers) consistently preferred the feeder at which trained foragers had fed (training feeder) over an identical feeder at which bees had never fed (control feeder) even when the training feeder was placed at a site where experienced foragers had never foraged. Through similar misdirection experiments, the effective radius of the scent beacon was determined to be greater than 6 and less than 12 m. Foragers may deposit this beacon during a sequence of departure behaviors performed at the feeder. Prior to leaving the feeder with a load of sugar solution, bees tended to perform the following sequence of behaviors: (1) spinning, (2) grooming, (3) abdomen dragging, (4) excreting anal droplets, and (5) producing sounds, although not all behaviors were performed prior to each departure or at all sucrose concentrations (0.5–2.5 m). As sucrose concentration increased, the number of newcomers significantly increased, and the number of experienced foragers producing sounds and spinning on the feeder increased. The exact source of the scent beacon remains a mystery. However, three important sources have been excluded. When choosing between identical paired feeders, foragers were not attracted to the feeders with (1) anal droplets, (2) extracts of sucrose solution at which foragers had fed, or (3) mandibular gland extracts. They were indifferent to the first two preparations and exhibited only typical alarm behavior towards the mandibular gland (MG) extract: they oriented towards the feeder with MG extract but consistently landed on the feeder with no MG extract. Other authors have suggested that Melipona foragers deposit anal droplets to attract recruits, however the frequency of anal droplet production and the mass of anal droplets produced by M. panamica foragers are negatively correlated with sucrose concentration. Thus the scent beacon is evidently not deposited with anal droplets, infused into the feeder solution, or produced by mandibular glands. Received: 2 September 1997 / Accepted after revision: 30 January 1998     

Relative importance and interactive effects of photosynthesis and food in two solar-powered sea slugs

Sacoglossans use chloroplasts taken from algal food for photosynthesis (kleptoplasty), but the adaptive significance of this phenomenon remains unclear. Two con-generic sacoglossans (Elysia trisinuata and E. atroviridis) were collected in 2009–2011 from Shirahama (33.69°N, 135.34°E) and Mukaishima (34.37°N, 133.22°E), Japan, respectively. They were individually maintained for 16 days under four experimental conditions (combination of light/dark and with/without food), and their survival rate and relative (=final/initial) weights were measured. Both light and food had positive effects on the survival in E. trisinuata, whereas no positive effects of light or food on survival were detected in E. atroviridis. Both light and food had positive effects on relative weights in both species, but light had smaller effects than food. A significant interaction term between light and food was detected in E. trisinuata (but not in E. atroviridis) in that only the presence of both resulted in weight gains. This result suggests that E. trisinuata can obtain sufficient additional energy from photosynthesis for sustaining growth when fresh chloroplasts are continuously supplied from algal food. In addition, fluorescence yield measurements showed that unfed individuals of both E. trisinuata and E. atroviridis lost photosynthetic activity soon (<4 and 4–8 days, respectively). In conclusion, photosynthesis may function to obtain supplementary nutrition for sustaining growth when food is available in sacoglossans with short-term functional kleptoplasty.     

The importance of agricultural lands for Himalayan birds in winter

The impacts of land‐use change on biodiversity in the Himalayas are poorly known, notwithstanding widespread deforestation and agricultural intensification in this highly biodiverse region. Although intact primary forests harbor many Himalayan birds during breeding, a large number of bird species use agricultural lands during winter. We assessed how Himalayan bird species richness, abundance, and composition during winter are affected by forest loss stemming from agriculture and grazing. Bird surveys along 12 elevational transects within primary forest, low‐intensity agriculture, mixed subsistence agriculture, and intensively grazed pastures in winter revealed that bird species richness and abundance were greatest in low‐intensity and mixed agriculture, intermediate in grazed pastures, and lowest in primary forest at both local and landscape scales; over twice as many species and individuals were recorded in low‐intensity agriculture than in primary forest. Bird communities in primary forests were distinct from those in all other land‐use classes, but only 4 species were unique to primary forests. Low‐, medium‐, and high‐intensity agriculture harbored 32 unique species. Of the species observed in primary forest, 80% had equal or greater abundance in low‐intensity agricultural lands, underscoring the value of these lands in retaining diverse community assemblages at high densities in winter. Among disturbed landscapes, bird species richness and abundance declined as land‐use intensity increased, especially in high‐intensity pastures. Our results suggest that agricultural landscapes are important for most Himalayan bird species in winter. But agricultural intensification—especially increased grazing—will likely result in biodiversity losses. Given that forest reserves alone may inadequately conserve Himalayan birds in winter, comprehensive conservation strategies in the region must go beyond protecting intact primary forests and ensure that low‐intensity agricultural lands are not extensively converted to high‐intensity pastures.     

The importance of handling time for the flight directionality in bees

Summary Individual workers of the honeybee (Apis mellifera), trained to collect food from a patch of artificial flowers, were used to test the following hypotheses about the mechanism leading to a decrease in flight directionality when moving from one flower to the next. Directionality decreases with (1) an increasing amount of energy taken from a flower, (2) an increasing amount of time spent on a flower, or (3) an increasing profitability of the flower, i.e. rate of nectar uptake. The bees were tested singly on an arrangement with equidistant flowers. They could move from a decision point forward, right, left, or backwards to the next flower. The rewards at the decision point were altered. When rewards at this point were compared that offered the same quality of nectar (50% sugar solution), the time hypothesis (2) was consistent with the observed behaviour of the bees. When conditions were compared that involved two different reward qualities (50% and 25% sugar solation), none of the original hypotheses could entirely account for the results.It is suggested that a slight modification of the time hypothesis would be consistent with the observations: The bees might possibly forget their arrival direction on the flower with increasing time, but forgetting the direction of the last flower visited is intensified with more concentrated rewards.     

The importance of groundwater discharge for plant species number in riparian zones

Riparian zones are hotspots of plant species richness in temperate and boreal biomes. The phenomenon is believed to be caused primarily by river-related processes, and upland influences on riparian zones have received relatively little attention. We investigated the importance of discharge of groundwater derived from uplands on riparian patterns in vascular plant species composition. We found that groundwater discharge areas in riparian zones were 36-209% more species rich than non-discharge areas, depending on spatial scale (1-50 m wide transects from annual high-water levels to summer low-water levels) and river (one free-flowing and one regulated). Higher nitrogen availability and less drought stress during low river stages are suggested as the major causes for the higher species diversity in discharge areas. Riparian zones lacking groundwater discharge lost more species following water-level regulation than did discharge areas. This indicates that groundwater discharge areas are more resistant to regulation because both individual plants and plant populations may grow larger in discharge areas. These results demonstrate that riparian zones are controlled by water and nutrient input from upland parts of catchments in ways that have been overlooked despite more than three decades of research into linkages between stream ecosystems and their valleys.     

Cryptic biodiversity effects: importance of functional redundancy revealed through addition of food web complexity

Interactions between predators and the degree of functional redundancy among multiple predator species may determine whether herbivores experience increased or decreased predation risk. Specialist parasites can modify predator behavior, yet rarely have cascading effects on multiple predator species and prey been evaluated. We examined influences of specialist phorid parasites (Pseudacteon spp.) on three predatory ant species and herbivores in a coffee agroecosystem. Specifically, we examined whether changes in ant richness affected fruit damage by the coffee berry borer (Hypothenemus hampei) and whether phorids altered multi-predator effects. Each ant species reduced borer damage, and without phorids, increasing predator richness did not further decrease borer damage. However, with phorids, activity of one ant species was reduced, indicating that the presence of multiple ant species was necessary to limit borer damage. In addition, phorid presence revealed synergistic effects of multiple ant species, not observed without the presence of this parasite. Thus, a trait-mediated cascade resulting from a parasite-induced predator behavioral change revealed the importance of functional redundancy, predator diversity, and food web complexity for control of this important pest.     

The obtaining of biosphere reserve decrees in Mexico: analysis of three cases

SUMMARY

During eight years, the Biological Research Center of the Northwest promoted the federal decrees to attain legal protection of three key zones for biodiversity conservation in Mexico: La Sierra de La Laguna, El Desierto del Vizcaíno, and E1 Archipiélago Revillagigedo Biosphere Reserves. In this work, we discuss the biological and socioeconomical importance of these three regions, the necessary steps to attain a Presidential decree in Mexico, and the required strategies to promote local and political support for each decree. In a country like Mexico, the promotion of one Presidential decree to declare a zone as a biosphere reserve must successfully address two different goals: the technical and the political. The technical phase can be successfully completed by a research centre or university in 6 to 12 months; while the political phase may or may not be successfully completed. If successful, in our experience, it can be attained with 2 to 96 months of continuous efforts.     

A new method for obtaining barnacle cement in the liquid state for polymerization studies

A new method for collecting barnacle cement in the liquid state is described. This permits studies on the transformation of cement from liquid to solid states not heretofore possible. Preliminary analyses showed that polymerization, i.e., the in vitro change from a clear liquid to an opaque solid mass is not affected by temperatures ranging from-10° to 45°C, by diluting with distilled water up to two-fold, or by treating with selective enzymes; some chemical inhibitors induce the formation of a white precipitate, possibly indicating denaturation of the protein. It is concluded that the liquid cement contains all the necessary components for self-assembly, progressively changing from a clear liquid to an opaque rubbery insoluble mass. The polymerization process is time-dependent and requires no exogenous catalyst. A mechanism that may be involved in the adhesion process of the barnacle is suggested.     

Accumulation of cadmium in the mussel Mytilus edulis: kinetics and importance of uptake via food and sea water

In a short-term (162 h) accumulation experiment with mussels Mytilus edulis exposed to 100 ppb Cd and fed algal cells (Phaeodactylum tricornutum) in 1986, it was found that uptake via food played an insignificant role compared to direct uptake from ambient water (19 S). From measurements of the filtration rate and Cd uptake rate, it was estimated that the fraction of Cd taken up per liter of water filtered was about 0.15%. The initial uptake of Cd was linear with time and about three times higher in fed than in starved mussels. From the measured uptake of Cd in starved mussels collected in 1982 and exposed to 10, 100 and 200 ppb in long-term experiments (up to 242 d), it was found that the Cd Accumulation rate was not linear with time, and that the Cd uptake was not directly proportional with the exposure concentration. Values as high as 100 to 1 300 ppm Cd (dry wt of soft parts) were measured. It was found that the Cd elimination rate was not directly proportional with the Cd body burden in long-term exposed mussels, thus indicating that a certain fraction of Cd may have been immobilized to metallothioneins.     

The evolution of food sharing in primates

The aim of this study is to explain the occurrence of food sharing across primates. Defined as the unresisted transfer of food, evolutionary hypotheses have to explain why possessors should relinquish food rather than keep it. While sharing with offspring can be explained by kin selection, explanations for sharing among unrelated adults are more controversial. Here we test the hypothesis that sharing occurs with social partners that have leverage over food possessors due to the opportunity for partner choice in other contexts. Thus, we predict that possessors should relinquish food to potential mates or allies, who could provide or withhold matings or coalitionary support in the future. We used phylogenetic analyses based on both maximum likelihood and Bayesian approaches in a sample of 68 primate species to test these predictions. The analyses strongly indicate that (1) sharing with offspring is predicted by the relative processing difficulty of the diet, as measured by the degree of extractive foraging, but not overall diet quality, (2) food sharing among adults only evolved in species already sharing with offspring, regardless of diet, and (3) male–female sharing co-evolved with the opportunity for female mate choice and sharing within the sexes with coalition formation. These results provide comparative support for the hypothesis that sharing is “traded” for matings and coalitionary support in the sense that these services are statistically associated and can thus be selected for. Based on this, we predict that sharing should occur in any species with opportunities for partner choice.     

Context-dependent effects of nestling growth trajectories on recruitment probability in the collared flycatcher

Nestling growth is known as an important determinant of fitness in altricial birds, but its evolutionary potential has been debated, and little is known about detailed patterns of current selection on growth. Relationships are often reported between nestling growth and attributes of nestlings and parents, but the interpretation of these depends on the advantages a given growth difference confers to the chicks. Increased growth may have positive, negative or context-dependent effects on offspring fitness, but these effects are largely unknown in natural populations. We measured growth trajectories of body mass in fostered broods of collared flycatchers (Ficedula albicollis) in 3 years of contrasting food conditions. We examined the growth of young and their recruitment probability to the breeding population in relation to year quality, hatching rank, sex, paternal age and paternal attractiveness. We also looked at the interactive effects of growth and intrinsic offspring attributes on recruitment probability. The predictors of nestling growth and those of recruitment did not agree. Moreover, the recruitment consequences of a given nestling growth rate were significantly influenced by nestling rank and paternal ornamentation. Differential recruitment effects of nestling growth in relation to parental traits and nestling attributes suggest that using growth as a generally applicable measure of nestling quality may not be justified. These findings also have implications for morphological evolution and the indicator value of sexual signals.     

The importance of age-related decline in forest NPP for modeling regional carbon balances.

We show the implications of the commonly observed age-related decline in aboveground productivity of forests, and hence forest age structure, on the carbon dynamics of European forests in response to historical changes in environmental conditions. Size-dependent carbon allocation in trees to counteract increasing hydraulic resistance with tree height has been hypothesized to be responsible for this decline. Incorporated into a global terrestrial biosphere model (the Lund-Potsdam-Jena model, LPJ), this hypothesis improves the simulated increase in biomass with stand age. Application of the advanced model, including a generic representation of forest management in even-aged stands, for 77 European provinces shows that model-based estimates of biomass development with age compare favorably with inventory-based estimates for different tree species. Model estimates of biomass densities on province and country levels, and trends in growth increment along an annual mean temperature gradient are in broad agreement with inventory data. However, the level of agreement between modeled and inventory-based estimates varies markedly between countries and provinces. The model is able to reproduce the present-day age structure of forests and the ratio of biomass removals to increment on a European scale based on observed changes in climate, atmospheric CO2 concentration, forest area, and wood demand between 1948 and 2000. Vegetation in European forests is modeled to sequester carbon at a rate of 100 Tg C/yr, which corresponds well to forest inventory-based estimates.     

The effects of seston food quality on planktonic food web patterns

In planktonic food webs, the conversion rate of plant material to herbivore biomass is determined by a variety of factors such as seston biochemical/elemental composition, phytoplankton cell morphology, and colony architecture. Despite the overwhelming heterogeneity characterizing the plant–animal interface, plankton population models usually misrepresent the food quality constraints imposed on zooplankton growth. In this study, we reformulate the zooplankton grazing term to include seston food quality effects on zooplankton assimilation efficiency and examine its ramifications on system stability. Using different phytoplankton parameterizations with regards to growth strategies, light requirements, sinking rates, and food quality, we examined the dynamics induced in planktonic systems under varying zooplankton mortality/fish predation, light conditions, nutrient availability, and detritus food quality levels. In general, our analysis suggests that high food quality tends to stabilize the planktonic systems, whereas unforced oscillations (limit cycles) emerge with lower seston food quality. For a given phytoplankton specification and resource availability, the amplitude of the plankton oscillations is primarily modulated from zooplankton mortality and secondarily from the nutritional quality of the alternative food source (i.e., detritus). When the phytoplankton community is parameterized as a cyanobacterium-like species, conditions of high nutrient availability combined with high zooplankton mortality led to phytoplankton biomass accumulation, whereas a diatom-like parameterization resulted in relatively low phytoplankton to zooplankton biomass ratios highlighting the notion that high phytoplankton food quality allows the zooplankton community to sustain relatively high biomass and to suppress phytoplankton biomass to low levels. During nutrient and light enrichment conditions, both phytoplankton and detritus food quality determine the extent of the limit cycle region, whereas high algal food quality increases system resilience by shifting the oscillatory region towards lower light attenuation levels. Detritus food quality seems to regulate the amplitude of the dynamic oscillations following enrichment, when algal food quality is low. These results highlight the profitability of the alternative food sources for the grazer as an important predictor for the dynamic behavior of primary producer–grazer interactions in nature.     

Monitoring waterbird abundance in wetlands: The importance of controlling results for variation in water depth

Wetland use by waterbirds is highly dependent on water depth, and depth requirements generally vary among species. Furthermore, water depth within wetlands often varies greatly over time due to unpredictable hydrological events, making comparisons of waterbird abundance among wetlands difficult as effects of habitat variables and water depth are confounded. Species-specific relationships between bird abundance and water depth necessarily are non-linear; thus, we developed a methodology to correct waterbird abundance for variation in water depth, based on the non-parametric regression of these two variables. Accordingly, we used the difference between observed and predicted abundances from non-parametric regression (analogous to parametric residuals) as an estimate of bird abundance at equivalent water depths. We scaled this difference to levels of observed and predicted abundances using the formula: ((observed − predicted abundance)/(observed + predicted abundance)) × 100. This estimate also corresponds to the observed:predicted abundance ratio, which allows easy interpretation of results. We illustrated this methodology using two hypothetical species that differed in water depth and wetland preferences. Comparisons of wetlands, using both observed and relative corrected abundances, indicated that relative corrected abundance adequately separates the effect of water depth from the effect of wetlands.     

The importance of experience in the interpretation of conspecific chemical signals

Foraging bumblebees scent mark flowers with hydrocarbon secretions. Several studies have found these scent marks act as a repellent to bee foragers. This was thought to minimize the risk of visiting recently depleted flowers. Some studies, however, have found a reverse, attractive effect of scent marks left on flowers. Do bees mark flowers with different scents, or could the same scent be interpreted differently depending on the bees’ previous experience with reward levels in flowers? We use a simple experimental design to investigate if the scent marks can become attractive when bees forage on artificial flowers that remain rewarding upon the bees’ return after having depleted them. We contrast this with bees trained in the more natural scenario where revisits to recently emptied flowers are unrewarding. The bees’ association between scent mark and reward value was tested with flowers scent marked from the same source. We find that the bees’ experience with the level of reward determines how the scent mark is interpreted: the same scent can act as both an attractant and a repellent. How experience and learning influence the interpretation of the meaning of chemical signals deposited by animals for communication has rarely been investigated.     

Increased production of faecal pellets by the benthic harpacticoid Paramphiascella fulvofasciata: importance of the food source

The re-use of faecal pellets in the water column before sinking to the seafloor is known as an important pathway in marine food webs. Especially planktonic copepods seems to be actively use their faecal pellets. Since benthic copepods (order Harpacticoida) live in the vicinity of their pellets, it remains unclear how important these pellets are for their feeding ecology. In the present study a laboratory experiment was conducted to analyse the importance of faecal pellets for the feeding ecology of the harpacticoid Paramphiascella fulvofasciata and its grazing pressure on two diatom species (Seminavis robusta, Navicula phyllepta). By quantifying the amount and volume of the produced faecel pellets in different treatments, it was tested to what extent the food source and the lack of faecal pellets would influence the production of faecal pellets. We found that the grazing pressure of P. fulvofasciata depended on the diatom density since only a top-down effect could be found on the smaller Navicula cells during its initial exponential growth phase. The grazer had a negative effect on the diatom growth and controlled the cell density to about 4,000 cells/cm². In spite of the fact that the addition of faecal pellets did not show a significant positive effect on the assimilation of diatoms, the removal of faecal pellets strongly promoted the pellet production. Especially when grazing on Navicula the harpacticoid P. fulvofasciata produced significantly more and smaller faecal pellets when the pellets were removed. This outcome illustrates the need for faecal pellets of this harpacticoid copepod when grazing on the diatom Navicula. Apart from its selection for smaller diatom cells, it was suggested that the colonisation of heterotrophic bacteria enriched these pellets. This study is the first to indicate that trophic upgrading occurs on faecal pellets and not only on the initial autotrophic food sources per se.