Schmeißfliegen (Calliphoridae) und vakuumverpackter Schinken

Blowflies (Calliphoridae) and vacuum-packed ham In a few cases blowfly maggots have been reported from vacuum-packed ham. The possibility of egg-hatching and larval development in the product was analysed. In experiments no hatching of blowfly eggs on vacuum-packed, boiled, sliced ham occurred. However, the eggs are not killed immediately; 1–4 days after the packing, they are still viable and when the wrapping is broken, hatching may occur. After a stay of 7–10 days on vacuum-packed ham, the viability of the eggs seems lost. In the actual case the risk of oviposition by blowflies on ham in the cannery and succeeding larval development in the product is considered to be very low.     

Influence of storage conditions on viability of quiescent copepod eggs (Acartia tonsa Dana): effects of temperature, salinity and anoxia

Copepods have proven to be an ideal source of live food for the production of marine fish larvae in aquaculture. Therefore, there is a need to develop new methods for production and storage of copepod eggs that can be hatched and used at fish farms. In the present study quiescent eggs of Acartia tonsa were stored for periods up to 35 weeks at different temperatures, salinities and oxygen conditions in a full factorial experiment. None of these storage conditions seemed to induce diapause in eggs even though this has been reported by other authors. The most promising storage conditions were those involving low temperature (<5°C), medium salinity (10–20 ppt) and anoxia. The practical aspects of these results for aquaculture are discussed.     

Effect of landscape structure on anopheline mosquito density and diversity in northern Thailand: Implications for malaria transmission and control

The influence of landscape structure on anopheline mosquito density and diversity was studied in a comparison of agricultural and forested landscapes in northern Thailand. Agriculture locations had significantly higher landscape diversity, more patches, smaller mean patch sizes, and more complex patch shapes than forest locations. Mosquito collections were undertaken during both dry and wet seasons from October 1997 to December 1999. The density of two forest-associated species, Anopheles maculatus s.s. and Anopheles minimus s.l., both primary malaria vectors in Thailand, was significantly higher in forest locations in at least one season. The density of two paddy field-associated species, Anopheles aconitus and Anopheles hyrcanus group did not differ between locations. Anopheles aconitus is a secondary malaria vector and An. hyrcanus group is not considered as a vector in Thailand. The density of An. minimus s.l. was positively related to forest mean patch size, various water and paddy field landscape metrics and negatively related to landscape diversity. Anopheles hyrcanus group was also positively related to water metrics. Anopheline species diversity was negatively related to landscape diversity. Forest fragmentation resulting from human economic activities often increases landscape heterogeneity, which may result in a reduction in anopheline species diversity, as was the case in this study. There are indications that the effect of fruit orchards on anopheline diversity might be different in the dry season compared to the wet season. Fruit orchard landscape metrics affected species diversity negatively in the dry season and positively in the wet season. One reason for this could be that pesticides are typically applied in fruit orchards during the dry season. The conversion of forests to fruit orchards is a major land-use change in northern Thailand. These results show the complexity of vector status in northern Thailand and that vector and agriculture pest control are intricately interrelated. It is therefore important to include both the public health and agricultural sectors in controlling malaria vectors in the country. Our results also indicate that if landscape management should be used for malaria control in northern Thailand large-scale reduction and fragmentation of forest cover would be needed. Such drastic actions do not agree well with current global objectives concerning forest and biodiversity conservation This revised version was published online in July 2006 with corrections to the Cover Date.     

Zur Flugaktivität von Trauermücken (Sciaridae) und Ephydridae in Treibhäusern und ihre Bedeutug für Bekämpfungsmaßnahmen

Zusammenfassung In einem Treibhaus wurden Bekämpfungsmaßnahmen (Räucherungen und Aerosol-Anwendung) mit nur kurzer Wirkung and den erwachsenen Trauermücken durchgeführt. In der Praxis erfolgt die Insektenbekämpfung in der Regel, wenn eine alarmierend hohe Insektendichte einschließlich harmloser Arten wieScatella sp. (Ephydridae), beobacht wurde. Eine Registrierung der Flugaktivität der Insekten in den Treibhäusen zeigte, daß dieInsektenbekämpfung gewöhnlich durchgeführt wird, wenn die Populationsdichte der Trauermücken zurückgeht. Im vorliegenden Fall mißlang die Bekämpfung. Offenbar ist eine wirksame Bekämpfung der adulten Trauermücken in Treibhäusern in der Praxis schwierig. Es ist anzunehmenm, daß die Aufzeichnung der jahreszeitlichen Fluktuation in der Flugaktivität der Trauermücken in Treibhäusern den richtigen Zeitpunkt für das Suchen nach Larven und für den Beginn von gegen diesc gerichteten Bekämpfungsmßnahmen ermöglicht.

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Studies on the flight activity of sciarids and ephydrids in greenhouses in regard to their importance for control measures

In greenhouses control measures of transient effect, viz. fumigation and aerosols were applied against adult sciarids (Sciaridae). In practice insect control was initiated, when an alarming high density of flies, including harmless species such asScatella sp. (Ephydridae) were observed. A record of the flight activity of insects in the greenhouses showed that generally insect control was carried out when the population densities of sciarids etc. were already declining and on the whole this measure failed. Apparently, an efficent control of a dult sciarids in greenhouses may be difficult in pracitice. It is suggested that a record of seasonal fluctuations in flight activity of sciarids in greenhouses might indicate the right moment for a search for larvae and for the initiation of control measures against the latter stages if necessary.

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Mit 2 Abbildungen     

Butter blend containing fish oil improves the level of n-3 fatty acids in biological tissues of hamster

Many studies have shown beneficial effects of long chain n-3 polyunsaturated fatty acids (PUFA) on human health. Regardless of the positive effects of n-3 PUFA, the intake of these fatty acids remains low. An approach to increase the intake of n-3 PUFA in the population is to incorporate fish oil into food. In the present study, fish oil was incorporated into butter blends by enzymatic interesterification. The aim of the study was to investigate the effects of this butter product in comparison with a commercial butter blend and a product produced by interesterification but without fish oil. Golden Syrian hamsters received hamster feed blended with one of the three butter products. After 6 weeks of feeding, the fatty acid compositions of plasma, erythrocytes, liver, brain, and visceral fat were determined. The intake of butter product with fish oil resulted in a higher level of n-3 PUFA in plasma, erythrocytes, and liver. The incorporation of n-3 PUFA was significantly higher in phospholipids than in triacylglycerols. The results suggest that enriching butter blends with small amounts of fish oil can be used as an alternative method for improving the level of n-3 PUFA in biological tissues.     

Adaptations to overwintering in the earthworm Dendrobaena octaedra: Genetic differences in glucose mobilisation and freeze tolerance

Geographic variation in freeze tolerance, glycogen storage and freeze-induced glucose mobilisation was investigated in the earthworm Dendrobaena octaedra. Specimens from 15 populations collected in Canada, Greenland and Europe were reared in the laboratory in a common-garden experiment to test whether glucose and glycogen concentrations correlated with genetic variation in freeze tolerance among the populations. Populations from Canada, Sweden, Poland and Finland did not differ much in their freeze tolerance and were able to tolerate freezing for 18 d down to at least −14 °C (lowest temperature tested). Specimens collected in a relatively warm climate (Denmark) were the least freeze tolerant, and also had the lowest concentrations of glucose when frozen at −2 °C. However, there was no clear evidence that glucose concentration is a determinant in the degree of freeze tolerance of D. octaedra when considering the whole assemblage of populations. The role of phylogenetic inertia was tested by looking for serial independence and no influence of phylogeny was detected in our findings allowing us to exclude the possibility that phylogenetic relatedness between populations is a major evolutionary factor explaining the observed differences for freeze tolerance and related traits. The size of the glycogen reserve was significantly correlated with the ability to tolerate freezing. Large glycogen reserves may be advantageous in very cold regions in order to maximise cryoprotectant production and/or as a source of energy for the anaerobic metabolism occurring during prolonged freezing.     

Seasonal aspects of sciarid emergence in arable land (Diptera: Sciaridae)

In April-October 1990-95 soil sciarids emerging in two Danish barley fields were recorded by means of emergence traps. In 1990-92 the fields were conventionally tilled, in the autumn of 1992 one of the fields was abandoned as annual set-aside (1993) and in 1994-95 most of the field was recropped. In the cropped and uncropped fields 480-527 ind. m⁻² and 369-433 ind. m⁻² emerged, respectively. Ten sciarid species were recorded, eight of which are well-known farmland inhabitants. Apparently, abandonment affected Scatopsciara atomaria negatively, whereas Corynoptera perpusilla was encouraged. The predominant species were probably bivoltine or trivoltine. In Lycoriella castanescens, Scatopsciara atomaria, Corynoptera perpusilla and Bradysia trivittata the female proportion increased significantly during the season. It is assumed that the primary sex ratio of the species is spanandrous. The seasonal change in sex ratio might arise from the unusual modes of reproduction demonstrated in Sciaridae. In Lycoriella castanescens, Bradysia trivittata and Corynoptera perpusilla a significant seasonal increase in wing length was recorded, whereas the wing length of Scatopsciara atomaria and Bradysia rufescens decreased significantly during the season. This suggests a seasonality in the production of large, potentially migrant females. In arable fields sciarid life history traits such as sex ratio, adult biometry and fecundity might be facultative.     

Law Enforcement in Community Forestry: Consequences for the Poor

Decentralised forest management is believed to hold potential for increased economic and social equity. Implications of the associated local forest law enforcement on livelihoods, however, are not well understood. This paper explores the impacts of local forest law enforcement with a focus on the poorest forest users in community-managed forests. A case study including 14 community forest groups in western Nepal was conducted in 2008. Methods included review of archival data, a stakeholder survey (n?=?211), and recall of forest crimes by a random household sample (n?=?252). Local forest law enforcement was found to detect far more crimes than district-level enforcement. Crimes are primarily small-scale unauthorised appropriation of products for subsistence use by poorer households and rules are lightly enforced. It is argued that local law enforcement, while apparently not economically harmful to the poorer in the short term, may be used to perpetuate existing wealth and cast-based social inequities.     

Effects of weather conditions on mast year frequency in beech (Fagus sylvatica L.) in Sweden

During the last two decades, an increase of the frequency ofnaturally regenerated beech seedlings has been reported. Thismay be due to an increased masting. In this investigation insouthern Sweden, mast year frequency, mast crop size and therelationships between mast year and climatic variables werestudied. Our analysis shows that while the average mast yearinterval was 4–6 years from the end of the seventeenthcentury up to the 1960s, the mean interval has decreased to2.5 years during the most recent 30 years, and there have beentwo consecutive mast years on two occasions during this laterperiod. Mast years have often followed years in which the temperaturein July and September was higher than the 30-year mean. However,there were significant variations in the amounts of beechnutsproduced between different mast years, and beechnut productionincreased with increasing site index. Climatic changes, especiallyincreases in temperature, may have been responsible for thehigher frequency of mast years, but increased atmospheric nitrogendeposition may also have been a contributory factor.