Host specificity of Asian parasitoids for potential classical biological control of <Emphasis Type="Italic">Drosophila suzukii</Emphasis>

The Asian spotted wing drosophila, Drosophila suzukii, has recently become a serious pest of soft fruits in Europe. Classical biological control through the introduction of larval parasitoids from its native range in Asia is presently being considered. However, host specificity of potential biological control agents has to be determined to avoid releasing species that may have unintended non-target impacts. Larvae of six different European non-target fly species and the target D. suzukii were exposed either on diet or blueberries to three Asian larval parasitoids, Asobara japonica, Leptopilina japonica, and Ganaspis cf. brasiliensis, and one European species, Leptopilina heterotoma. Asobara japonica showed the lowest specificity, attacking and developing in all Drosophilidae. Leptopilina japonica successfully parasitized two non-target Drosophilidae, D. melanogaster and D. subobscura, with one singly progeny emerging from D. immigrans. Ganaspis cf. brasiliensis had the highest level of specificity but variations occurred between two geographical populations tested. A Japanese population was strictly specific to D. suzukii, whereas another population from China parasitized D. suzukii, D. melanogaster and sporadically D. subobscura. The European L. heterotoma successfully developed in D. melanogaster, D. subobscura and occasionally in D. immigrans, but nearly all eggs and larvae in D. suzukii were encapsulated. These results show that Ganaspis cf. brasiliensis is the species with the highest potential for biological control, but more studies are needed on its taxonomic status and the existence of biotypes or cryptic species varying in their specificity before field releases can be conducted in Europe.     

Most fish destined for fishmeal production are food‐grade fish

Marine fisheries target and catch fish both for direct human consumption (DHC) as well as for fishmeal and fish oil, and other products. We derived the fractions used for each for 1950–2010 by fishing country, and thus provide a factual foundation for discussions of the optimal use of fisheries resources. From 1950 to 2010, 27% (~20 million tonnes annually) of globally reconstructed marine fisheries landings were destined for uses other than DHC. Importantly, 90% of fish destined for uses other than DHC are food‐grade or prime food‐grade fish, while fish without a ready market for DHC make up a much smaller proportion. These findings have implications for how we are using fish to feed ourselves or, more appropriately, how we are not using fish to feed ourselves.     

Long-term lack of transmission of Aujeszky's disease virus (ADV) in a chronically infected Swedish weaner pig producing herd

A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation.     

Functional properties of soils formed from biochemical ripening of dredged sediments—subsidence mitigation in delta areas

Journal of Soils and Sediments - In delta areas, dense networks of canals have been developed through time and have to be periodically dredged. Lowering the groundwater level in delta areas deepens...     

Herd diagnosis of low pathogen diarrhoea in growing pigs – a pilot study

Background

The major indication for antibiotic use in Danish pigs is treatment of intestinal diseases post weaning. Clinical decisions on antibiotic batch medication are often based on inspection of diarrhoeic pools on the pen floor. In some of these treated diarrhoea outbreaks, intestinal pathogens can only be demonstrated in a small number of pigs within the treated group (low pathogen diarrhoea). Termination of antibiotic batch medication in herds suffering from such diarrhoea could potentially reduce the consumption of antibiotics in the pig industry. The objective of the present pilot study was to suggest criteria for herd diagnosis of low pathogen diarrhoea in growing pigs.Data previously collected from 20 Danish herds were used to create a case series of clinical diarrhoea outbreaks normally subjected to antibiotic treatment. In the present study, these diarrhoea outbreaks were classified as low pathogen (<15% of the pigs having bacterial intestinal disease) (n =5 outbreaks) or high pathogen (≥15% of the pigs having bacterial intestinal disease) (n =15 outbreaks). Based on the case series, different diagnostic procedures were explored, and criteria for herd diagnosis of low pathogen diarrhoea were suggested. The effect of sampling variation was explored by simulation.

Results

The diagnostic procedure with the highest combined herd-level sensitivity and specificity was qPCR testing of a pooled sample containing 20 randomly selected faecal samples. The criteria for a positive test result (high pathogen diarrhoea outbreak) were an average of 1.5 diarrhoeic faecal pools on the floor of each pen in the room under investigation and a pathogenic bacterial load ≥35,000 per gram in the faecal pool tested by qPCR. The bacterial load was the sum of Lawsonia intracellularis, Brachyspira pilosicoli and Escherichia coli F4 and F18 bacteria per gram faeces. The herd-diagnostic performance was (herd-level) diagnostic sensitivity =0.99, diagnostic specificity =0.80, positive predictive value =0.94 and negative predictive value =0.96.

Conclusions

The pilot study suggests criteria for herd diagnosis of low pathogen diarrhoea in growing pigs. The suggested criteria should now be evaluated, and the effect of terminating antibiotic batch medication in herds identified as suffering from low pathogen diarrhoea should be explored.

Electronic supplementary material

The online version of this article (doi:10.1186/2046-0481-67-24) contains supplementary material, which is available to authorized users.     

Temperature-dependent oxide removal from manganese- and iron oxide-coated soil redox bars

Purpose

Soil temperature is a fundamental parameter affecting not only microbial activity but also manganese (Mn^III,IV) and iron (Fe^III) oxide reduction rates. The relationship between Mn^III,IV oxide removal from oxide-coated redox bars is missing at present. This study investigated the effect of variable soil temperatures on oxide removal by Mn^III,IV and Fe^III oxide-coated redox bars in water-saturated soil columns in the laboratory.

Materials and methods

The Mn coatings contained the mineral birnessite, whereas the Fe coatings contained a mixture of ferrihydrite and goethite. Additionally, platinum (Pt) electrodes designed to measure the redox potential (E_H) were installed in the soil columns, which were filled with either a humic topsoil with an organic carbon (C_org) content of 85 g kg^?1 (pH 5.8) or a subsoil containing 2 g C_org kg^?1 (pH 7.5). Experiments were performed at 5, 15, and 25 °C.

Results and discussion

Although elevated soil temperatures accelerated the decrease in E_H after water saturation in the topsoil, no E_H decreases regardless of soil temperature occurred in the subsoil. Besides soil temperature, the importance of soil organic matter as an electron donor is highlighted in this case. Complete removal of the Mn^III,IV oxide coating was observed after 28, 14, and 7 days in the soil columns filled with topsoil at 5, 15, and 25 °C, respectively. Along the Fe redox bars, Fe^III reducing conditions first appeared at 15 °C and oxide removal was enhanced at 25 °C because of lower E_H, with the preferential dissolution of ferrihydrite over goethite as revealed by visual differences in the Fe^III oxide coating. Oxide removal along redox bars followed the thermodynamics of the applied minerals in the order birnessite > ferrihydrite > goethite.

Conclusions

In line with Van’t Hoff’s rule, turnover rates of Mn^III,IV and Fe^III oxide reduction increased as a result of increased soil temperatures. Taking into account the stability lines of the designated minerals, E_H-pH conditions were in accordance with oxide removal. Soil temperature must therefore be considered a master variable when evaluating the oxide removal of redox bars employed for the monitoring of soil redox status.

     

Vitamin D status of wild Ricord's iguanas (Cyclura ricordii) and captive and wild rhinoceros iguanas (Cyclura cornuta cornuta) in the Dominican Republic.

Calcidiol (25-hydroxyvitamin D) values are reported for 22 wild Ricord's iguanas (Cyclura ricordii) and seven wild rhinoceros iguanas (Cyclura cornuta cornuta). Calcitriol (1,25-hydroxyvitamin D) values are reported for 12 wild Ricord's iguanas and seven wild rhinoceros iguanas. These animals were captured as part of a larger health assessment study being conducted on Ricord's iguanas in Isla Cabritos National Park, Dominican Republic. A total of 13 captive rhinoceros iguanas held outdoors at Parque Zoológico Nacional were also sampled for comparison. Mean concentrations of 25-hydroxyvitamin D were 554 nmol/L (222 ng/ml) with a range of 250-1,118 nmol/L (100-448 ng/ml) for wild Ricord's iguanas, 332 nmol/L (133 ng/ml) with a range of 260-369 nmol/L (104-148 ng/ml) for wild rhinoceros iguanas, and 317 nmol/L (127 ng/ml) with a range of 220-519 nmol/L (88-208 ng/ml) for captive rhinoceros iguanas. On the basis of these results, serum concentrations of at least 325 nmol/L (130 ng/ml) for 25-hydroxyvitamin D should be considered normal for healthy Ricord's and rhinoceros iguanas.     

Mortality and fish welfare

Mortality has received insufficient attention as a fish welfare topic. Here, we aim to prompt fish farming stakeholders to discuss fish mortalities in relation to welfare. Mortality in farmed fish populations is due to a variety of biotic and abiotic causes, although it is often difficult to differentiate between underlying and immediate causes of mortality. Most mortality appears to occur during episodes associated with disease outbreaks and critical periods (in development or production). Most causes of mortality can be assumed to be associated with suffering prior to death. As mortality rates in farmed fish populations are suspected to rank amongst the highest in commonly farmed vertebrate species, mortality should be a principal fish welfare issue. Long-term mortality rates can be used as a retrospective welfare performance indicator and short-term mortality rates as an operational welfare indicator. Scrutiny of mortality records and determining causes of death will enable action to be taken to avoid further preventable mortality. The welfare performance of fish farms should only be judged on levels of predictable and preventable mortality. Fish farmers will already be monitoring mortality due to commercial and legal requirements. As profitability in fish farming is directly linked to survival, confronting mortality should ultimately benefit both fish and farmers.     

Temperature control of the distributional range of five C3 grass species in the uKhahlamba-Drakensberg Park,KwaZulu-Natal,South Africa

Global climate change is expected to influence the distribution of global biodiversity. C₄ and C₃ perennial grasses co-occur in the fire-prone KwaZulu-Natal uKhahlamba-Drakensberg grasslands, with C₃ grass species occurring at cooler locations in the mountain range and C₄ grass species at warmer locations. If a warming climate is expected to cause a contraction in the ranges of C₃ grasses, evidence of temperature controlling current distributions is required. This study modelled the distribution of five C₃ grass species, namely Tenaxia stricta, Tenaxia disticha, Festuca costata, Merxmuellera drakensbergensis and Merxmuellera stereophylla, to temperature-related surrogate variables using presence–absence data collected across the environmental heterogeneity of the mountain range. Distributions of each species, and of all species combined, were modelled using generalised additive models. These temperature-related variables accounted for the distribution of all five species, least so for F. costata. Four species could therefore contract in range in response to climate change, whereas F. costata is least likely to have a range contraction directly related to a warming climate and could experience a range expansion owing to the fertilising effect of increased [CO₂].