The ecological effects of trichloroacetic acid in the environment

Trichloroacetic acid (TCAA) is a member of the family of compounds known as chloroacetic acids, which includes mono-, di- and trichloroacetic acid. The significant property these compounds share is that they are all phytotoxic. TCAA once was widely used as a potent herbicide. However, long after TCAA's use as a herbicide was discontinued, its presence is still detected in the environment in various compartments. Methods for quantifying TCAA in aqueous and solid samples are summarized. Concentrations in various environmental compartments are presented, with a discussion of the possible formation of TCAA through natural processes. Concentrations of TCAA found to be toxic to aquatic and terrestrial organisms in laboratory and field studies were compiled and used to estimate risk quotients for soil and surface waters. TCAA levels in most water bodies not directly affected by point sources appear to be well below toxicity levels for the most sensitive aquatic organisms. Given the phytotoxicity of TCAA, aquatic plants and phytoplankton would be the aquatic species to monitor for potential effects. Given the concentrations of TCAA measured in various soils, there appears to be a risk to terrestrial organisms. Soil uptake of TCAA by plants has been shown to be rapid. Also, combined uptake of TCAA from soil and directly from the atmosphere has been shown. Therefore, risk quotients derived from soil exposure may underestimate the risk TCAA poses to plants. Moreover, TCE and TCA have been shown to be taken up by plants and converted to TCAA, thus leading to an additional exposure route. Mono- and di-chloroacetic acids can co-occur with TCAA in the atmosphere and soil and are more phytotoxic than TCAA. The cumulative effects of TCAA and compounds with similar toxic effects found in air and soil must be considered in subsequent terrestrial ecosystem risk assessments.     

Effects of food-borne ZnO nanoparticles on intestinal microbiota of common carp (Cyprinus carpio L.)

Environmental Science and Pollution Research - Ingestion of nanoparticles (NPs) with antimicrobial properties may disrupt the balance of intestinal microbiota. To investigate the effects of zinc...     

Sex-dependent immune response in a semelparous spider

Previous studies on arthropods showed that seasonality and parity in breeding considerably impact the direction of sex differences in immunocompetence, and it has been suggested that life span and the time window available for breeding play key roles in shaping sex-differences in immunity. One proposed mechanism behind this phenomenon is differential investment into life history traits in sexes. Here, we tested whether in a seasonally breeding semelparous arthropod sexes differ in their immunocompetence, predicting that females would show weaker immune response than males. We compared encapsulation efficiency (a well-established and widely used method for assessing immunocompetence) of freshly matured, virgin males and females of the lycosid spider Pardosa agrestis (Westring, 1861). On average, males mounted stronger immune response than females and the extent of encapsulation was positively associated with prosoma length in males, but not in females. Also, time until maturation was positively related to the extent of encapsulation in both sexes, but did not significantly affect adult prosoma length. We propose that sex-difference in encapsulation is likely shaped by combined effects of relatively higher costs of reproduction in females, narrow time window of reproductive activity, and the absence of trade-off between current and future reproduction.     

Optimal annual routines: new tools for conservation biology?

Many applied problems in ecology and conservation require prediction, and population models are important tools for that purpose. Formerly, the majority of predictive population models were based on matrix models. As the limitations of classical matrix models have become clearer, the use of individual-based models has increased. These models use behavioral rules imposed at the level of the individual to establish the emergent consequences of those rules at the population level. Individual behaviors in such models use an array of different rule types, from empirically derived probabilities to long-term fitness considerations. There has been surprisingly little discussion of the strengths and weaknesses of these different rule types. Here, we consider different strategies for modeling individual behaviors, together with some problems associated with individual-based models. We propose a novel approach based on modeling optimal annual routines. Annual routines allow individual behaviors to be predicted over a whole annual cycle within the context of long-term fitness considerations. Temporal trade-offs between different behaviors are automatically included in annual routine models, overcoming some of the primary limitations of other individual-based models. Furthermore, as well as population predictions, individual behaviors and indices of condition are emergent features of annual routine models. We show that these can be more sensitive to environmental change than population size, offering alternative, repeatable metrics for monitoring population status. Annual routine models provide no panacea for the problems of data limitations in predictive population modeling. However, as a result of their ability to deal with life-history trade-offs, as well as their potential for relatively rapid and accurate validation and parameterization, we suggest that annual routine models have strong potential for predictive population modeling in applied conservation settings.     

1‐Aminobenzotriazole increases glutathione‐s‐transferase activity of maize

Abstract

Glutathione‐S‐transferase (GST) activity of maize (Zea mays L.) seedlings treated with 1‐aminobenzotriazole (ABT) derivatives and/or EPTC were measured using EPTC‐sulfoxide as substrate. Both safeners and ABT derivatives significantly elevated the GST activity in the concentrations needed for effective safening action. ABT is considered as an inhibitor of plant cytochrome P‐450 monooxygenases (P‐450) and, because of this, used to study herbicide mode of action. Our data indicate that ABT has multiple effects on plants influencing not only P‐450 but GST as well. Thus the role of ABT in herbicide metabolism needs reconsideration.     

The effect of dominance hierarchy on the use of alternative foraging tactics: a phenotype-limited producing-scrounging game

Group living is thought to be advantageous for animals, though it also creates opportunities for exploitation. Using food discovered by others can be described as a producer-scrounger, frequency-dependent game. In the game, scroungers (parasitic individuals) do better than producers (food finders) when scroungers are rare in the group, but they do worse when scroungers are common. When the individuals' payoffs do not depend on their phenotype (i.e. a symmetric game), this strong negative frequency dependence leads to a mixed stable solution where both alternatives obtain equal payoffs. Here, we address the question of how differences in social status in a dominance hierarchy influence the individuals' decision to play producer or scrounger in small foraging groups. We model explicitly the food intake rate of each individual in a dominance-structured foraging group, then calculate the Nash equilibrium for them. Our model predicts that only strong differences in competitive ability will influence the use of producing or scrounging tactics in small foraging groups; dominants will mainly play scrounger and subordinates will mostly use producer. Since the differences in competitive ability of different-ranking individuals likely depend on the economic defendability of food, our model provides a step towards the integration of social foraging and resource defence theories. Received: 30 July 1997 / Accepted after revision: 15 November 1997     

Sexual dimorphism in immune function changes during the annual cycle in house sparrows

Difference between sexes in parasitism is a common phenomenon among birds, which may be related to differences between males and females in their investment into immune functions or as a consequence of differential exposure to parasites. Because life-history strategies change sex specifically during the annual cycle, immunological responses of the host aiming to reduce the impact of parasites may be sexually dimorphic. Despite the great complexity of the immune system, studies on immunoecology generally characterise the immune status through a few variables, often overlooking potentially important seasonal and gender effects. However, because of the differences in physiological and defence mechanisms among different arms of the immune system, we expect divergent responses of immune components to environmental seasonality. In male and female house sparrows (Passer domesticus), we measured the major components of the immune system (innate, acquired, cellular and humoral) during four important life-history stages across the year: (1) mating, (2) breeding, (3) moulting and (4) during the winter capture and also following introduction to captivity in aviary. Different individuals were sampled from the same population during the four life cycle stages. We found that three out of eight immune variables showed a significant life cycle stage × sex interaction. The difference in immune response between the sexes was significant in five immune variables during the mating stage, when females had consistently stronger immune function than males, while variables varied generally non-significantly with sex during the remaining three life cycle stages. Our results show that the immune system is highly variable between life cycle stages and sexes, highlighting the potential fine tuning of the immune system to specific physiological states and environmental conditions.