Omnivory and grazer functional composition moderate cascading trophic effects in experimental <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> habitats

We tested the relative strength of direct versus indirect effects of an aquatic omnivore depending on the functional composition of grazers by manipulating the presence of gastropod and amphipod grazers and omnivorous shrimp in outdoor mesocosms. By selectively preying upon amphipods and reducing their abundance by 70–80%, omnivorous shrimp favoured the dominance of gastropods. While gastropods were the main microalgal grazers, amphipods controlled macroalgal biomass in the experiment. However, strong predation on the amphipod by the shrimp had no significant indirect effects on macroalgal biomass, indicating that when amphipod abundances declined, complementary feeding by the omnivore on macroalgae may have suppressed a trophic cascade. Accordingly, in the absence of amphipods, the shrimp grazed significantly on green algae and thereby suppressed the diversity of the macroalgal community. Our experiment demonstrates direct consumer effects by an omnivore on both the grazer and producer trophic levels in an aquatic food web, regulated by prey availability.     

Salps in the Lazarev Sea,Southern Ocean: I. Feeding dynamics

Feeding dynamics of the Antarctic salps Ihlea racovitzai and Salpa thompsoni were studied in the Lazarev Sea in fall 2004, summer 2005–2006 and winter 2006. Pigment concentrations in the guts of both species were positively correlated with ambient surface chlorophyll a (chl a). No evidence was found for salp clogging even at dense surface concentrations of up to 7 μg chl a L⁻¹. However, gut pigment concentrations had a lower range than ambient pigment concentrations, suggesting that salps increased retention times of ingested material in low-food environments. For medium-sized I. racovitzai and S. thompsoni, estimated individual daily rations reached 7–10 and >100% of body carbon in winter and summer, respectively. Daily respiratory needs of I. racovitzai and S. thompsoni accounted for 28 and 22% of daily carbon assimilation based on pigment ingestion rates in winter, and for 2 and 1% in summer, respectively. The grazing impact of the salp populations on the phytoplankton standing stock was negligible during all seasons due to generally low salp densities. Fatty acid trophic biomarkers in the salps suggest high year-round contributions of flagellates and modest contributions of diatoms to the salp’s diet. These markers showed low seasonal variability for I. racovitzai. The more pronounced seasonality of trophic markers in S. thompsoni were likely related to their generally deeper residence depth in winter linked to a seasonal alternation of sexual and asexual generations.     

Origins and mechanisms leading to aneuploidy in human eggs

The gain or loss of a chromosome—or aneuploidy—acts as one of the major triggers for infertility and pregnancy loss in humans. These chromosomal abnormalities affect more than 40% of eggs in women at both ends of the age spectrum, that is, young girls as well as women of advancing maternal age. Recent studies in human oocytes and embryos using genomics, cytogenetics, and in silico modeling all provide new insight into the rates and potential genetic and cellular factors associated with aneuploidy at varying stages of development. Here, we review recent studies that are shedding light on potential molecular mechanisms of chromosome missegregation in oocytes and embryos across the entire female reproductive life span.     

Subsocial behaviour and brood adoption in mixed-species colonies of two theridiid spiders

Cooperation and group living often evolves through kin selection. However, associations between unrelated organisms, such as different species, can evolve if both parties benefit from the interaction. Group living is rare in spiders, but occurs in cooperative, permanently social spiders, as well as in territorial, colonial spiders. Mixed species spider colonies, involving closely related species, have rarely been documented. We examined social interactions in newly discovered mixed-species colonies of theridiid spiders on Bali, Indonesia. Our aim was to test the degree of intra- and interspecific tolerance, aggression and cooperation through behavioural experiments and examine the potential for adoption of foreign brood. Morphological and genetic analyses confirmed that colonies consisted of two related species Chikunia nigra (O.P. Cambridge, 1880) new combination (previously Chrysso nigra) and a yet undescribed Chikunia sp. Females defended territories and did not engage in cooperative prey capture, but interestingly, both species seemed to provide extended maternal care of young and indiscriminate care for foreign brood. Future studies may reveal whether these species adopt only intra-specific young, or also inter-specifically. We classify both Chikunia species subsocial and intra- and interspecifically colonial, and discuss the evolutionary significance of a system where one or both species may potentially benefit from mutual tolerance and brood adoption.     

Managing Alaska’s National Parks in an era of uncertainty: an evaluation of scenario planning workshops

Regional Environmental Change - Scenario planning is a flexible tool used to assess a broad range of plausible, relevant, divergent, and challenging futures, for short-term responses and long-term...     

Metal diffusion properties of a Nafion-coated porous membrane in an aquatic passive sampler system

A cellulose acetate membrane, positioned in a passive sampler system, was coated with the perfluorinated polymer Nafion. Aqueous metal transport through the membrane and the Nafion film was investigated. The Nafion-coated membrane prevents the transport of metals bound to natural organic material to the receiving phase in the passive sampler, while copper associated with small synthetic ligands pass through the Nafion film. Increasing thickness of the Nafion film decreases the metal uptake rate to the receiving phase in the passive sampler and increases the response time. A decreased response time for the passive sampler would provide a better estimation of rapid changes in concentration, particularly for dynamic aquatic systems such as urban runoff. Limited biofouling protection with the Nafion coating was demonstrated by growth inhibition of natural periphyton communities on glass surfaces.     

Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic hyperaccumulator Pteris vittata L

Pteris vittata was the first terrestrial plant known to hyperaccumulate arsenic (As). However, it is unclear how As hyperaccumulation influences nutrient uptake by this plant. P. vittata fern was grown in soil spiked with 0-500 mg As kg(-1) in the greenhouse for 24 weeks. The concentrations of essential macro- (P, K, Ca, and Mg) and micro- (Fe, Mn, Cu, Zn, B and Mo) elements in the fronds of different age were examined. Both macro- and micronutrients in the fronds were found to be within the normal concentration ranges for non-hyperaccumulators. However, As hyperaccumulation did influence the elemental distribution among fronds of different age of P. vittata. Arsenic-induced P and K enhancements in the fronds contributed to the As-induced growth stimulation at low As levels. The frond P/As molar ratios of 1.0 can be used as the threshold value for normal growth of P. vittata. Potassium may function as a counter-cation for As in the fronds as shown by the As-induced K increases in the fronds. The present findings not only demonstrate that P. vittata has the ability to maintain adequate concentrations of essential nutrients while hyperaccumulating As from the soil, but also have implications for soil management (fertilization in particular) of P. vittata in As phytoextraction practice.     

Integration of natural behavior in housing systems

This paper deals with how the natural behavior of animals kept for production can be integrated when planning new housing systems or making changes to existing housing systems. Natural behavior can be defined as the repertoire of different behaviors animals show when kept in environments where they can carry out behaviors created in the evolutionary process. Motivation and innate behaviors are important aspects of natural behavior, and hindering them may lead to abnormal behavior and stress. One should first get a basic knowledge about the species-specific behavior in the wild or a seminatural environment. Thereafter, key stimuli and key features for normal behavior should be worked out, where after a reduction in space, development of a pen, scientific testing, modification, and finally testing the function in a larger scale should be carried out. Examples of housing of calves during the milk period and housing of sows around farrowing are given.     

Effects of compost and phosphate amendments on arsenic mobility in soils and arsenic uptake by the hyperaccumulator,Pteris vittata L

Chinese brake fern (Pteris vittata L.), an arsenic (As) hyperaccumulator, has shown the potential to remediate As-contaminated soils. This study investigated the effects of soil amendments on the leachability of As from soils and As uptake by Chinese brake fern. The ferns were grown for 12 weeks in a chromated-copper-arsenate (CCA) contaminated soil or in As spiked contaminated (ASC) soil. Soils were treated with phosphate rock, municipal solid waste, or biosolid compost. Phosphate amendments significantly enhanced plant As uptake from the two tested soils with frond As concentrations increasing up to 265% relative to the control. After 12 weeks, plants grown in phosphate-amended soil removed >8% of soil As. Replacement of As by P from the soil binding sites was responsible for the enhanced mobility of As and subsequent increased plant uptake. Compost additions facilitated As uptake from the CCA soil, but decreased As uptake from the ASC soil. Elevated As uptake in the compost-treated CCA soil was related to the increase of soil water-soluble As and As(V) transformation into As(III). Reduced As uptake in the ASC soil may be attributed to As adsorption to the compost. Chinese brake fern took up As mainly from the iron-bound fraction in the CCA soil and from the water-soluble/exchangeable As in the ASC soil. Without ferns for As adsorption, compost and phosphate amendments increased As leaching from the CCA soil, but had decreased leaching with ferns when compared to the control. For the ASC soil, treatments reduced As leaching regardless of fern presence. This study suggest that growing Chinese brake fern in conjunction with phosphate amendments increases the effectiveness of remediating As-contaminated soils, by increasing As uptake and decreasing As leaching.     

Different ejaculate delivery strategies in first versus subsequent matings in the swallowtail butterfly Papilio machaon L.

Summary Evidence suggests that males incur costs in producing ejaculates. Therefore some discrimination should be expected with respect to their pattern of allocating ejaculates. In a laboratory study, males of the European swallowtail butterfly Papilio machaon were mated with conspecific virgin females up to six times. The weight of the spermatophore and of the accessory substances delivered by males, the duration of mating, and the number of sperm in ejaculates were measured. The weight of the first spermatophore was related to male weight but that of accessory substances was not. The weight of the spermatophore delivered by males upon remating was always less than that of the first spermatophore. Second spermatophores Produced by males were smallest when delivered on the day after the first mating and increased asymptotically to about half the initial size with time elapsed since the first mating. Copula duration was highest for males remating on the day after the first mating but decreased to the duration of the first mating for males that were remated on the third day after the first mating or later. The weight of accessory substances delivered by males and the number of sperm in ejaculates were also higher in first matings compared to all subsequent matings. Both of two males that were handpaired on three consecutive days after the first mating produced a cumulative ejaculate mass equalling that transferred at the first mating. Thus the fact that males delivered smaller ejaculates upon remating on the third day after the first mating or later requires explanation, especially in view of the fact that copulations were not prolonged. We argue that the male ejaculate delivery strategy in mildly polyandrous species should be to mate for the first time with virgin females, when a maximum size ejaculate should be delivered, and then to maximize the number of matings. The rationale behind the male shift towards smaller ejaculate sizes delivered at subsequent matings is that: (1) the size of the ejaculate that can be produced is dependent on the time elapsed since the last mating; (2) the abundance of virgin females decreases as the flight season proceeds; and (3) there is an inverse relationship between the size and number of ejaculates that a male can produce in his life-time.