Heterocyst Structure Alteration and O2-Mediated Inhibition of Dinitrogen Fixation by Trichlorfon in Anabaena PCC 7119

The involvement of a primary inhibition of dinitrogen fixationin the toxic effect of trichlorfon in cyanobacteria has beeninvestigated. Significant inhibition of nitrogenase activitycan be detected 3 h after the addition of insecticide to batchcultures of Anabaena PCC 7119. Recovery of nitrogenase activitystarts between 6–12 h after removal of the insecticide,suggesting a requirement for the induction of new heterocysts.Under anaerobic conditions the inhibitory effect of the insecticideis largely prevented. Biochemical analysis indicates that envelopeglycolipids exist in trichlorfon-treated cultures. However,ultrastructural examination shows heterocyst deterioration andthe failure of the inner glycolipid layer of the heterocystenvelope. Our data are consistent with the view that destabilizationof the heterocyst envelope is the first target of insecticidalaction. Inhibition of dinitrogen fixation and growth have alsobeen shown in the cyanobacteria Gloeothece PCC 6501, NostocUAM 205, and Chlorogloeopsis PCC 6912.     

Psychological and Evolutionary Evidence for Altruism

Sober and Wilson have recentlyclaimed that evolutionary theory can do whatneither philosophy nor experimental psychologyhave been able to, namely, ``break the deadlock'in the egoism vs. altruism debate with anargument based on the reliability of altruisticmotivation. I analyze both their reliabilityargument and the experimental evidence ofsocial psychology in favor of altruism in termsof the folk-psychological ``laws' and inferencepatterns underlying them, and conclude thatthey both rely on the same patterns. I exposethe confusions that have led Sober and Wilsonto defend a reliability argument whilerejecting the experimental evidence of socialpsychology.     

Fragmentation causes rarity in common marmosets in the Atlantic forest of northeastern Brazil

The purpose of this study was to investigate the population status of the common marmosets, Callithrix jacchus, in one of their main habitats, the northeastern Atlantic forest of Brazil, where only 2% of its original area remains as small and isolated forest fragments, to determine long-term viable populations. The study was carried out in 15 forest fragments, measuring from 3,478.3 ha (the largest) to 6 ha, which were invariably subjected to high human impact. Line transect surveys were carried out between January 2002 and December 2004, along transects measuring from 350 to 4,000 m, between 0500 h and 0900 h. Common marmosets were registered in 73% (n = 11) of the forest fragments, were not recorded in the largest one, the Coimbra Forest, and group sizes varied from 1 to 4 individuals. A negative significant relationship was detected between the size of the fragment and the number of sightings of common marmosets. It is shown that the number of groups of common marmosets dwelling in this highly impacted landscape is nowadays lower than necessary for long-term survival. Additionally, smaller fragments having more groups suggests that they live in total association with humans, which assure their subsistence through the supply of introduced and exotic foods.     

Evolutionary game theory meets social science: Is there a unifying rule for human cooperation?

Evolutionary game theory has shown that human cooperation thrives in different types of social interactions with a PD structure. Models treat the cooperative strategies within the different frameworks as discrete entities and sometimes even as contenders. Whereas strong reciprocity was acclaimed as superior to classic reciprocity for its ability to defeat defectors in public goods games, recent experiments and simulations show that costly punishment fails to promote cooperation in the IR and DR games, where classic reciprocity succeeds. My aim is to show that cooperative strategies across frameworks are capable of a unified treatment, for they are governed by a common underlying rule or norm. An analysis of the reputation and action rules that govern some representative cooperative strategies both in models and in economic experiments confirms that the different frameworks share a conditional action rule and several reputation rules. The common conditional rule contains an option between costly punishment and withholding benefits that provides alternative enforcement methods against defectors. Depending on the framework, individuals can switch to the appropriate strategy and method of enforcement. The stability of human cooperation looks more promising if one mechanism controls successful strategies across frameworks.     

Organophosphorus and Organochlorine Pesticides Bioaccumulation by Eichhornia crassipes in Irrigation Canals in an Urban Agricultural System

A natural wetland in Mexico City Metropolitan Area is one of the main suppliers of crops and flowers, and in consequence its canals hold a high concentration of organochlorine (OC) and organophosphorus (OP) pesticides. There is also an extensive population of water hyacinth (Eichhornia crassipes), which is considered a plague; but literature suggests water hyacinth may be used as a phytoremediator. This study demonstrates bioaccumulation difference for the OC in vivo suggesting their bioaccumulation is ruled by their log K_ow, while all the OP showed bioaccumulation regardless of their log K_ow. The higher bioaccumulation factors (BAF) of the accumulated OC pesticides cannot be explained by their log K_ow, suggesting that the OC pesticides may also be transported passively into the plant. Translocation ratios showed that water hyacinth is an accumulating plant with phytoremediation potential for all organophosphorus pesticides studied and some organochlorine pesticides. An equation for free water surface wetlands with floating macrophytes, commonly used for the construction of water-cleaning wetlands, showed removal of the pesticides by the wetland with room for improvement with appropriate management.     

Analysis of temporal fluctuations in numbers of sexually mature Anastrepha ludens females over an extensive citrus area in northeastern Mexico

The Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most important pests in citrus‐growing areas in Mexico. In this study, we analyzed the temporal fluctuation of sexually mature females of A. ludens populations with respect to the availability of commercial hosts and climatic factors, as well as population data of females over an extensive citrus area in northeastern Mexico. The numbers of mature females were treated as proportions and analyzed with generalized linear mixed models with a binomial error distribution. Results revealed positive effects on proportions of mature females when commercial hosts (Valencia orange and grapefruit) were available at both medium and high levels, whereas negative effects on proportions were observed when commercial hosts were scarcely available. Monthly analyses indicated positive trends on proportion in March, April, October, and November, whereas negative trends were seen in January and June. A low capture of mature females during the late summer and the onset of winter suggests transitional phenological processes across the year. Overall, no relationships were observed between proportions with temperature and the total number of females; however, a positive relationship was observed between proportion and rainfall. These findings provide insight into the reproductive phenology of A. ludens with practical implications for fruit sampling, as well as for the autocidal or chemical control in an areawide integrated pest management (AW‐IPM) approach in citrus‐growing areas of northeastern Mexico.