Worker senescence and the sociobiology of aging in ants

Senescence, the decline in physiological and behavioral function with increasing age, has been the focus of significant theoretical and empirical research in a broad array of animal taxa. Preeminent among invertebrate social models of aging are ants, a diverse and ecologically dominant clade of eusocial insects characterized by reproductive and sterile phenotypes. In this review, we critically examine selection for worker life span in ants and discuss the relationship between functional senescence, longevity, task performance, and colony fitness. We did not find strong or consistent support for the hypothesis that demographic senescence in ants is programmed, or its corollary prediction that workers that do not experience extrinsic mortality die at an age approximating their life span in nature. We present seven hypotheses concerning how selection could favor extended worker life span through its positive relationship to colony size and predict that large colony size, under some conditions, should confer multiple and significant fitness advantages. Fitness benefits derived from long worker life span could be mediated by increased resource acquisition, efficient division of labor, accuracy of collective decision-making, enhanced allomaternal care and colony defense, lower infection risk, and decreased energetic costs of workforce maintenance. We suggest future avenues of research to examine the evolution of worker life span and its relationship to colony fitness and conclude that an innovative fusion of sociobiology, senescence theory, and mechanistic studies of aging can improve our understanding of the adaptive nature of worker life span in ants.     

Forest Fragmentation and Bird Extinctions: San Antonio Eighty Years Later

We report on the extent of bird extinctions at San Antonio, a fragmented cloud forest site in the western Andes of Colombia, for which surveys dating back to 1911 and 1959 an available. In 1911, 128 forest bird species were present in San Antonio. Twenty-four species had disappeared by 1959, and since then 16 more species have gone locally extinct, for a total of 40 species or 31% of the original avifauna. We analyzed patterns of extinction in relation to geographic distribution and foraging guilds. We found that in this montane assemblage, being at the limits of the altitudinal distribution was the main correlate of extinction; 37% of the extinct species were at the upper limit of their altiudinal distribution. We also found that the most vulnerable guilds were the understory insectivores and the large canopy frugivores. Our study illustrates the extent of bird extinctions that are currently undocumented in the highly fragmented forests of the northern Andes, where the absence of baseline information on the fauna of unaltered forests is a limiting factor for the development of conservation and management plans. We stress the need to establish data bases and long-term monitoring projects for the Andean fauna.     

Lipid components as a measure of nutritional condition in fish larvae (Pleuragramma antarcticum) in East Antarctica

Pleuragramma antarcticum is a key component of the neritic assemblages in the Antarctic coastal waters. Larvae of this species were sampled from 2008 to 2011 in the Dumont d’Urville Sea (East Antarctica). The lipid class composition [triacylglycerols (TAG), cholesterol (Chol) and polar lipids (PL)] of larvae was measured to assess the larval condition. The total amount of lipids was linearly related to the quantity of structural polar lipids, suggesting that growth is favored over lipid storage. The TAG:Chol ratio showed interannual variability in the condition of fish larvae, probably related to prey availability. Nevertheless, the essential fatty acids composition of polar lipids illustrates that larvae with low levels of TAG:Chol could be either growing or under starvation. Only the combination of a low TAG:Chol ratio and low polar lipids content, which can also be mobilized during starvation periods, allowed identification of larvae in poor condition. This lipid condition index should be of great assistance to evaluate the probability of survival of P. antarcticum larvae in long-term monitoring. It has widespread applicability and should also be useful in the diagnosis of nutritional condition in other species.     

Quaternary geographical sibling speciation and population structuring in the Eastern Atlantic skates (suborder Rajoidea) Raja clavata and R. straeleni

The European Raja clavata and the South African R. straeleni are marine skates which exhibit highly conserved morphological and ecological traits. Owing to this, taxonomic and evolutionary relationships between the two taxa have not yet fully elucidated. Here, we have tested the hypothesis that restricted gene flow and genetic divergence between these taxa might be associated with climatic/oceanographic discontinuities by surveying genetic variation in ten geographical samples at control region (CR) and amplified fragment length polymorphism (AFLP) loci. The clustering of CR haplotypes in two reciprocally monophyletic clades consistent with taxon zoogeography and the significant AFLP F values between the European and South African populations indicated the two taxa as recently diverged peripatric sibling species. Within each species, significant spatial genetic heterogeneity among samples at both markers revealed population structuring. We argued that structured populations and isolated sibling species might represent two stages of geographical speciation.     

A case for urban liveability from below: exploring the politics of water and land access for greater liveability in Kampala,Uganda

ABSTRACT

Improving urban liveability and prosperity is commonly set as a priority in urban development plans and policy around the world. Several annual reports produced by international consulting firms, media, and global agencies rank the liveability of cities based on a set of indicators, to represent the quality of life in these cities. The higher is the ranking, the more liveable is the city. In this paper, we argue that such quantitative approaches to framing and addressing urban liveability challenges leave little room to reflect on people's experiences of this liveability, which cannot be expressed through numbers. To illustrate our argument, we draw on empirical evidence of urban liveability challenges in access to water and land in Kampala, the capital city of Uganda, ranked recently as the most liveable East African city by various global agencies and media outlets. By showing that increasing the number of water connections does not guarantee improved access to water and sanitation in the long run, first, we demonstrate how urban liveability challenges are tightly linked with land-title issues in the city. Second, we highlight the political game-playing between the central government, the opposition, the traditional leadership, and the slum dwellers in governance processes of service delivery. Finally, by arguing that urban liveability can be enhanced by broadening political participation in city development planning, we discuss some of the strategies that can be used by communities to make collective claims towards improving their quality of life and the environment.     

Food resource use in a tropical eastern Pacific tidepool fish assemblage

An understanding of the trophic organization patterns of tropical littoral fish assemblages can contribute to the knowledge of key ecosystem processes while simultaneously assisting to validate large-scale biogeographic patterns (i.e. latitudinal patterns in fish herbivory). In the present study, the diets of eight fish species inhabiting the tide pools of a rocky shore on the western coast of Colombia (tropical eastern Pacific) are documented. A total of 17 prey items were identified, with a major representation (average percent by weight) of crabs and macroalgae items in the guts of all species. Small crustacean prey items (crabs, shrimps, copepods and amphipods) dominated the diets of most species, but consumption of macroalgae and diatoms by a significant number of species was also observed. We identified four significant trophic guilds within the assemblage using multivariate techniques (cluster analysis and nMDS): an omnivorous guild, consisting of Malacoctenus zonifer and the smallest size class of Bathygobius ramosus; a small-prey carnivorous guild, consisting of the intermediate size classes of B. ramosus and the smallest size class of Gobiesox adustus; a large-prey carnivorous guild, consisting of both largest size classes of B. ramosus and G. adustus; and an herbivorous guild consisting of Abudefduf concolor, A. troschelii and Chaenomugil proboscideus. The diet of two species slightly overlapped those of the rest of the assemblage and did not conform to any guild (Echidna nocturna and Halichoeres aestuaricola). It is hypothesised that guild formation may be a consequence of aggregation of species at abundant resources in the intertidal zone rather than a direct consequence of inter-specific competition. Ontogenetic changes in diets were observed in two resident species of the assemblage (B. ramosus and G. adustus). The latitudinal trend for herbivory inside this tropical assemblage is discussed in comparison with similar temperate studies in the eastern Pacific.     

Evaluation of a simultaneous sampling method of PAHs, PCDD/Fs and dl-PCBs in ambient air

The Stockholm Convention on Persistent Organic Pollutants (POPs) was signed in May 2001 by 127 countries. Currently, 12 substances are regulated by the convention, and the work on finding new candidate chemicals to the convention has started. Among these 12 substances, dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are the objects of this study. There are no European standard methods for the simultaneous determination of these microorganic compounds, together with polycyclic aromatic hydrocarbons (PAHs) in ambient air--they must be referred to three different methods developed by the U.S. Environmental Protection Agency (EPA). The quali-quantitative analysis of these microorganic pollutants is an important challenge due to the low concentrations at which they may be present. In this study, the development of a simplified, alternative, fast and affordable sampling method for the determination of PAHs, PCDDs, PCDFs and PCBs in ambient air was performed. The sampling time was extended from 24 h to 7 d in order to enrich the sample, to fall within the instrumental limits of detection and to reduce the number of samples to be processed and, therefore, errors that may arise. First of all, experiments with labelled standards were conducted in the research area of Montelibretti (rural station, which is sited about 20 km northeast of Rome), with the purpose of optimizing sampling efficiency. Finally, the method was applied to the analysis of these compounds in the air of a suburban area with small industrial plants in order to evaluate the feasibility of the proposed sampling method system, by comparing concentrations of native compounds acquired during simultaneous daily and weekly sampling.     

Organochlorine pesticides and polychlorinated biphenyls in common buzzard (<Emphasis Type="Italic">Buteo buteo</Emphasis>) from Sicily (Italy)

In the present study, we investigated the concentrations and distribution of organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs) in intestine, liver, and muscle samples of 11 common buzzards (Buteo buteo) from Sicily used as bioindicator for monitoring pollution in environment. All samples of common buzzards were collected at the “Recovery Center of Wild Fauna” of Palermo, through the Zooprophilactic Institute. Quantitative determination of OCs and PCBs in the samples examined has been carried out using HRGC-ECD and GC-MS. The results obtained show the presence of concentrations of ∑DDT and ∑PCB in almost all samples. Regarding ∑DDT (4,4^′-DDE, 2,4^′-DDD, 4,4^′-DDD, 2,4^′-DDT, and 4,4^′-DDT), the highest concentrations were found in intestine (0.411 ± 0.050 μg/g) followed by muscle (0.130 ± 0.017 μg/g) and liver samples (0.109 ± 0.014 μg/g). As regards the ∑PCB congeners (PCB-28, PCB-52, PCB-95, PCB-99, PCB-101, PCB-110, PCB-138, PCB-146, PCB-149, PCB-151, PCB-153, PCB-170, PCB-177, PCB-180, PCB-183, and PCB-187), the highest concentrations were found in intestine (1.686 ± 0.144 μg/g) followed by liver (1.064 ± 0.162 μg/g) and muscle samples (0.797 ± 0.078 μg/g). Our data deserve particular attention not only for their significance but especially because they were recorded in Sicily, a region with a very low risk of environmental pollution due to the shortage of industries.     

Minor crops for export: A case study of boscalid,pyraclostrobin, lufenuron and lambda-cyhalothrin residue levels on green beans and spring onions in Egypt

Dissipation rates of boscalid [2-chloro-N-(4′ -chlorobiphenyl-2-yl)nicotinamide], pyraclostrobin [methyl 2-[1-(4-chlorophenyl) pyrazol-3-yloxymethyl]-N-methoxycarbanilate], lufenuron [(RS)-1-[2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)phenyl]-3-(2,6-difluorobenzoyl)urea] and λ-cyhalothrin [(R)-cyano(3-phenoxyphenyl)methyl (1S,3S)-rel-3-[(1Z)-2-chloro-3,3,3-trifluoro-1-propenyl]-2,2-dimethylcyclopropanecarboxylate] in green beans and spring onions under Egyptian field conditions were studied. Field trials were carried out in 2008 in a Blue Nile farm, located at 70 kilometer (km) from Cairo (Egypt). The pesticides were sprayed at the recommended rate and samples were collected at pre-determined intervals. After treatment (T₀) the pesticide residues in green beans were 7 times lower than in spring onions. This is due to a different structure of vegetable plant in the two crops. In spring onions, half-life (t_1/2) of pyraclostrobin and lufenuron was 3.1 days and 9.8 days respectively. At day 14th (T₁₄) after treatment boscalid residues were below the Maximum Residue Limit (MRL) (0.34 versus 0.5 mg/kg), pyraclostrobin and λ -cyhalothrin residues were not detectable (ND), while lufenuron residues were above the MRL (0.06 versus 0.02 mg/kg). In green beans, at T₀, levels of boscalid, lufenuron and λ -cyhalothrin were below the MRL (0.28 versus 2 mg/kg; ND versus 0.02 mg/kg; 0.06 versus 0.2 mg/kg, respectively) while, after 7 days treatment (T₇) pyraclostrobin residues were above the MRL (0.03 versus 0.02 mg/kg). However, after 14 days the residue level could go below the MRL (0.02 mg/kg), as observed in spring onions.     

Removal of emerging contaminants from wastewater using advanced treatments. A review

Environmental Chemistry Letters - The rise of emerging contaminants in waters challenges the scientific community and water treatment stakeholders to design remediation techniques that are simple,...