Life Cycle of the Oriental Compost Worm Perionyx Excavatus (Oligochaeta)

In order to exploit the concept of using vermiculture as biotechnology for waste control and protein production, the life cycle of the vermicomposting species, Perionyx excavatus, was studied. The development, growth and reproduction of P. excavatus  were investigated. Urine free cattle manure with a moisture content of 76-83% and a temperature of 25°C was used as substrate. Data were gathered over a period of 300 days. It was found that mating is not a prerequisite for cocoon production, which starts at the mean age of 24 days. Maturation was attained at the age of approximately 21 days. Cocoons were produced at a mean rate of 1,1 cocoons per worm per day. The mean incubation period of cocoons produced by batches of worms was 18,7 days with a mean hatching success of 63,4%. The mean incubation period of cocoons produced by single worms was 20,4 days with a mean hatching success of 40,4%. As a rule only one worm hatched per cocoon. The life cycle of this species is presented diagrammatically

Predicting how many animals will be where: how to build, calibrate and evaluate individual-based models

Individual-based models (IBMs) can simulate the actions of individual animals as they interact with one another and the landscape in which they live. When used in spatially-explicit landscapes IBMs can show how populations change over time in response to management actions. For instance, IBMs are being used to design strategies of conservation and of the exploitation of fisheries, and for assessing the effects on populations of major construction projects and of novel agricultural chemicals. In such real world contexts, it becomes especially important to build IBMs in a principled fashion, and to approach calibration and evaluation systematically. We argue that insights from physiological and behavioural ecology offer a recipe for building realistic models, and that Approximate Bayesian Computation (ABC) is a promising technique for the calibration and evaluation of IBMs. IBMs are constructed primarily from knowledge about individuals. In ecological applications the relevant knowledge is found in physiological and behavioural ecology, and we approach these from an evolutionary perspective by taking into account how physiological and behavioural processes contribute to life histories, and how those life histories evolve. Evolutionary life history theory shows that, other things being equal, organisms should grow to sexual maturity as fast as possible, and then reproduce as fast as possible, while minimising per capita death rate. Physiological and behavioural ecology are largely built on these principles together with the laws of conservation of matter and energy. To complete construction of an IBM information is also needed on the effects of competitors, conspecifics and food scarcity; the maximum rates of ingestion, growth and reproduction, and life-history parameters. Using this knowledge about physiological and behavioural processes provides a principled way to build IBMs, but model parameters vary between species and are often difficult to measure. A common solution is to manually compare model outputs with observations from real landscapes and so to obtain parameters which produce acceptable fits of model to data. However, this procedure can be convoluted and lead to over-calibrated and thus inflexible models. Many formal statistical techniques are unsuitable for use with IBMs, but we argue that ABC offers a potential way forward. It can be used to calibrate and compare complex stochastic models and to assess the uncertainty in their predictions. We describe methods used to implement ABC in an accessible way and illustrate them with examples and discussion of recent studies. Although much progress has been made, theoretical issues remain, and some of these are outlined and discussed

Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources

We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > $10^3$ confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples

Models for Type Ia supernovae and related astrophysical transients

We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we point out the challenges resulting from the multi-physics multi-scale nature of the problem and discuss possible numerical approaches to meet them in hydrodynamical explosion simulations and radiative transfer modeling. We give examples of how these methods are applied to several explosion scenarios that have been proposed to explain distinct subsets or, in some cases, the majority of the observed events. In case we comment on some of the successes and shortcoming of these scenarios and highlight important outstanding issues.Comment: 20 pages, 2 figures, review published in Space Science Reviews as part of the topical collection on supernovae, replacement corrects typos in the conclusions sectio

Spatial and temporal variation in cadmium body loads of four intertidal invertebrates from False Bay, South Africa

The original publication is available at http://africanzoology.journals.ac.za/pub.Increasing urbanization and industrialization along the coastal areas of False Bay in South Africa can endanger coastal ecosystems because of increasing metal pollution. To obtain baseline data on contamination levels in the intertidal zone, cadmium (Cd) body loads of four invertebrate species were measured seasonally over a period of 15 months from different sites within the bay. Specimens of Tetraclita serrata (barnacle), Oxystele sinenses (periwinkle), Cymbula oculus (limpet) and Choromytilus meridionalis (mussel) were collected and analysed to determine temporal changes in Cd body burdens. Cd concentrations were also measured in water and sediments. Cd concentrations in the intertidal animals varied considerably between sampling sites and between seasons and also occasionally between species. All four species accumulated Cd in their bodies to levels several times higher than environmental concentrations. No significant difference could be shown between the Cd concentrations in the gastropod grazers and the filter-feeders. The highest mean body load of Cd (70.67 μg/g dry weight) for a single sampling occasion was measured in the sessile barnacles (T. serrata) collected at Rooi-Els. The highest mean Cd concentration (11.95 μg/g) for the bay as a whole was measured in the limpet C. oculus. Two-way analysis of variance indicated that spatial (location) rather than temporal (seasonal) factors affected Cd concentrations in the invertebrates. Cd concentrations in False Bay sometimes exceeded the norms or water quality standards.Publisher's versio

The influence of exposure history to lead on the lysosomal response in Eisenia fetida (Oligochaeta)

In this study groups of the epigeic earthworm species Eisenia fetida were exposed experimentally for different periods to sublethal concentrations of Pb(NO3)2. The lysosomal membrane fragility response of coelomocytes was used as a biomarker to explore the cytotoxity of Pb by determining the neutral red retention times (NRRTs) and correlating them with different body loads of Pb. Previously unexposed worms exposed to different low concentrations of Pb(NO3)2 for 4 weeks demonstrated a clear dose-response relationship between NRRTs and body burdens of Pb. The NRRTs of growing worms with a previous (ancestral) exposure history, exposed to an elevated concentration of Pb and measured over time, fluctuated around a mean of 41min and no dose-related relationship could be demonstrated. Worms with a long-term history of exposure to Pb of more than 36 months had a mean body burden of 177.5±61.5mg/kg Pb and a mean NRRT of 57.8±3.1min, which was significantly lower than that of uncontaminated, control worms with a mean time of 61.9±3.4min and a mean body burden of 86.3±47.2mg/kg. No significant differences were found between weight changes of "clean" and preexposed worms when they were experimentally exposed to sublethal concentrations of Pb. This study provided evidence that the lysosomal biomarker response for Pb may not persist at the same level in worms with a previous history of Pb exposure, possibly making it less sensitive as a tool for comparing responses to Pb in field populations of earthworms. © 2003 Elsevier Science (USA). All rights reserved.Articl

The impact of organophosphate pesticides in orchards on earthworms in the Western Cape, South Africa

Earthworm population density was measured in and adjacent to an orchard in an agricultural area in the Western Cape, South Africa. Worm densities were very low in orchards (22/m2) compared to adjacent uncultivated fields (152/m2) at a distance from the orchards. The possible effect of organophosphate pesticides on the earthworms was investigated. Background soil concentrations of chlorpyrifos prior to the start of the spraying season were low (0.2-2.7 μg/kg) but persistent for up to 6 months after the last spraying event, and the pesticide was, as a result of rainfall, transported to nontarget areas by runoff. Background concentrations of azinphos methyl were higher than those of chlorpyrifos (1.6-9.8 μg/kg) but not detectable 2 weeks after a spraying event. Azinphos methyl was mostly transported by wind (spray drift) to adjacent areas. A microcosm study indicated effects of chlorpyrifos on earthworms as determined by measuring biomass change and Cholinesterase inhibition. It is concluded that earthworms were affected detrimentally by the pesticides due to chronic (chlorpyrifos) and intermittent (azinphos methyl) exposure. © 2005 Elsevier Inc. All rights reserved.Articl

Biomarker response and biomass change of earthworms exposed to chlorpyrifos in microcosms

Background levels of chlorpyrifos and earthworm abundance were determined in an orchard and adjacent areas on a farm in the Western Cape, South Africa before these areas were again sprayed with this organophosphate. The background concentrations ranged from 0.2 μg/kg dm in the spray drift area adjacent to the orchard to 10.18 μg/kg dm on the slope in the run off area. In the target area the chlorpyrifos concentrations varied from a mean of 15.25±10.0 μg/kg directly after spraying to a mean of 7.0±0.9 μg/kg 6 months later and in the nontarget area they varied from a mean of 55.0±35 μg/kg to 12.0±5 μg/kg after 6 months. Chlorpyrifos was therefore still present in the field soils, but at lower concentrations, up to 6 months after the last spraying event. Earthworm abundance and population densities were very low. Only Aporrectodea caliginosa was found and the densities were much lower in the orchards (22 per m2) than in the nontarget areas (98.3 per m2). Microcosm studies were undertaken to relate biomarker responses to chlorpyrifos with biomass changes. Microcosms were filled with soil from the same areas and earthworms of the species A. caliginosa were introduced. The microcosms were treated with a series of concentrations of chlorpyrifos in the laboratory under controlled conditions. These concentrations were chosen to fall within the background ranges found in the soils. The biomass of the worms was determined regularly for a period of 5 weeks and worms in a state of estivation were noted. Earthworms were removed from the microcosms for biomarker tests: for cholinesterase (ChE) inhibition assays every week and for a neutral red retention determination 2 weeks after the exposures started. The most prominent biomass loss was noted in earthworms exposed to the highest pesticide concentration of 8.0 μg/kg. Estivation was higher among earthworms exposed to higher exposure concentrations. Inhibition of ChE increased with higher exposure concentrations and with time but there was no clear dose-related response. A clear dose-related response with exposure concentration was established for the neutral red retention assay. A correlation between ChE inhibition and biomass change existed directly after the second application of chlorpyrifos. © 2005 Elsevier Inc. All rights reserved.Articl

Quantitative changes in the digestive gland cells of the snail Helix aspersa after exposure to the fungicide copper oxychloride

This study investigated the relationship between accumulated copper in the digestive gland of Helix aspersa, after exposure to the fungicide copper oxychloride, and quantitative changes in the digestive gland cells of this snail. Snails were exposed to 80 and 240μgg-1 copper oxychloride for 6 weeks. Histological sections of digestive glands were analyzed by means of computer-assisted image analysis. Results indicate that copper is strongly accumulated in the digestive gland and that this organ is the main site of copper accumulation in the snail body. Also, as a result of copper accumulation in the digestive gland, measurable changes in epithelium cell height and area of this organ occur. In the case of cell height, these changes are dose-related. It is concluded that changes in digestive gland cells, as a result of copper oxychloride exposure, may possibly serve as biomarkers of exposure to this fungicide. © 2003 Elsevier Inc. All rights reserved.Articl