Local adaptation studies and conservation: Parasite–host interactions between the endangered freshwater mussel Unio crassus and its host fish

1. Parasite–host interactions can involve strong reciprocal selection pressure, and may lead to locally adapted specializations. The highly threatened unionoid mussels are temporary parasites on fish, but local adaptation has not yet been investigated for many species.
2. Patterns of local adaptation of one of Europe's most threatened unionoids, the thick‐shelled river mussel (Unio crassus) were investigated. Eurasian minnows (Phoxinus phoxinus) from two rivers (separate drainage areas) were cross‐infested in the laboratory with sympatric and allopatric mussel larvae, while bullheads (Cottus gobio), inhabiting only one of the rivers, were infested with sympatric or allopatric mussel larvae. Larval encystment, juvenile mussel excystment and survival were measured.
3. For one river, but not the other, juvenile excystment from P. phoxinus was highest when infested with sympatric mussels. The opposite pattern was found for C. gobio in this river, where juvenile excystment and post‐parasitic juvenile survival from allopatric C. gobio were highest. The results thus cannot confirm local adaptation of U. crassus to P. phoxinus in the study rivers, as excystment was not consistently higher in all sympatric mussel–host combinations, whereas there were potential maladaptive signs of U. crassus in relation to C. gobio. There was no loss of encysted larvae 3 days after infestation until juvenile excystment. Most juveniles were excysted between 17 and 29 days after infestation, and the numbers of excysted juveniles increased with fish size.
4. The results have implications for parasite–host ecology and conservation management with regard to unionoid propagation and re‐introduction. This includes the need to (1) test suitability and adaptation patterns between U. crassus and multiple host fish species, (2) evaluate the suitability of certain unionoids and host fish strains after more than 3 days, and (3) determine whether large fish produce more juvenile mussels than smaller fish.

     

The effect of food type (formulated diet vs. natural) and fish size on feed utilization in common sole,Solea solea (L.)

This study compares the effect of food type (formulated diet vs. natural food) and fish size on protein and energy utilization efficiencies for growth in common sole, Solea solea (L.). Replicate groups of common sole (mean initial body weight ± SD was 45.7 g ± 2.1 and 111.2 g ± 4.2) received the diets at five (natural feed) or four (formulated diet) feeding levels. The protein utilization efficiency for growth (k_gCP) was higher (P > 0.001) in common sole fed ragworms than in common sole fed the formulated diet (respectively, 0.40 and 0.31). Likewise, the energy utilization efficiency for growth (k_gGE) was higher (P = 0.001) in common sole fed ragworms than in common sole fed the formulated diet (respectively, 0.57 and 0.33). The protein maintenance requirement was not different between food types (P = 0.64) or fish size (P = 0.41) being on average 0.82 g kg^?0.8 day^?1. The energy maintenance requirement was not different between food type (P = 0.390) but differed between fish size (P = 0.036). The gross energy maintenance requirement of small common sole was 35 kJ g^?0.8 day^?1. The gross energy maintenance requirement of large common sole was 25 kJ g^?0.8 day^?1. In conclusion, the low growth of common sole fed formulated diets was related to reduced feed utilization.     

Phenological and physiological evaluation of first and second cropping periods of sorghum and maize crops

Environmental conditions influence phenology and physiological processes of plants. It is common for maize and sorghum to be sown at two different periods: the first cropping (spring/summer) and the second cropping (autumn/winter). The phenological cycle of these crops varies greatly according to the planting season, and it is necessary to characterize the growth and development to facilitate the selection of the species best adapted to the environment. The aim of this study was to characterize phenological phases and physiological parameters in sorghum and maize plants as a function of environmental conditions from the first cropping and second cropping periods. Two parallel experiments were conducted with both crops. The phenological characterization was based on growth analyses (plant height, leaf area and photoassimilate partitioning) and gas exchange evaluations (net assimilation rate, stomatal conductance, transpiration and water-use efficiency). It was found that the vegetative stage (VS) for sorghum and maize plants was 7 and 21 days, respectively, longer when cultivated during the second cropping. In the first cropping, the plants were taller than in the second cropping, regardless of the crop. The stomatal conductance of sorghum plants fluctuated in the second cropping during the development period, while maize plants showed decreasing linear behaviour. Water-use efficiency in sorghum plants was higher during the second cropping compared with the first cropping. In maize plants, in the second cropping, the water-use efficiency showed a slight variation in relation to the first cropping. It was concluded that the environmental conditions as degree-days, temperature, photoperiod and pluvial precipitation influence the phenology and physiology of both crops during the first and the second cropping periods, specifically cycle duration, plant height, leaf area, net assimilation rate, stomatal conductance and water-use efficiency, indicating that both crops respond differentially to environmental changes during the growing season.     

Feeding ragworm (Nereis virens Sars) to common sole (Solea solea L.) alleviates nutritional anaemia and stimulates growth

Common sole fed with commercial pellets develop anaemia and are restricted in their growth performance. The anaemia can be the result of a difference in feed intake, a nutritional deficiency, an inflammatory response to infection or combinations of these aspects. In this study, it was investigated whether feeding ragworm would alleviate the anaemia and stimulate growth. Sole were fed one of three diets: a commercial feed, a commercial feed treated with ragworm extract or chopped ragworm. By comparing groups, three hypotheses were tested: (1) feeding ragworm alleviates the anaemia and positively affectS the sole's metabolic performance reflected in feed intake, feed efficiency and growth; (2) anaemia is alleviated by a higher feed intake when feeding ragworm and (3) anaemia is caused by an inflammatory response to infection. The sole fed with a commercial diet suffered from anaemia. Feeding sole with ragworm alleviated the anaemia as the average haematocrit level nearly doubled in these fish as compared to fish fed pellets. Investigation of the expression of genes in the liver indicated that the anaemia in sole fed pellets is a nutritional anaemia and not an anaemia due to an inflammatory response. Sole fed ragworm showed improved growth which may be a consequence of the higher haematocrit levels in these fish increasing their oxygen carrying capacity. Addition of ragworm extract to the pellets levelled the feed intake between pellets and ragworm, but did not improve the anaemic state of sole and had only a limited effect on growth.     

Umweltvorsorge über den Tag hinaus

Zusammenfassung Die Erkenntnis, da? die beste Umweltpolitik darin besteht, Umweltbelastungen von vornherein soweit wie m?glich zu vermeiden, statt sie erst nachtr?glich in ihren Auswirkungen zu bek?mpfen, ist unter dem Eindruck bedrohlicher Eingriffe in das „System Umwelt” unterdessen zum wichtigsten Grundsatzprinzip der Umweltaktions-programme—auch dem der EG—erkl?rt worden. Die praxisbezogene Umsetzung dieses Grundprinzips einer vorausschauenden Umweltplanung setzt allerdings voraus, da? zuerst einmal überhaupt genügend geeignete Informationen über Zustand und Leistungsf?higkeit der Umwelt zur Verfügung stehen und da? darüber hinaus eine entscheidungsorientierte Implementierung dieser Informationen auch tats?chlich erfolgen kann. Beide Voraussetzungen sind heute in der Regel kaum erfüllt. Den Bemühungen der EG, hier einen nicht zuletzt auch stimulierenden Beitrag auf Gemeinschaftsebene zu leisten, sollen vor allem die beiden in Angriff genommenen Gemeinschaftsaktionen „?kologische Kartierung” und „Umweltvertr?glichkeitsprüfung” genügen. Beide Aktionen erg?nzen sich in mancher Hinsicht. Für die Aktion „Umweltvertr?glichkeitsprüfung” ist bereits im Laufe des n?chsten Jahres mit geeigneten Vorschl?gen der EG-Kommission an den EG-Ministerrat zu rechnen. Die „?kologische Kartierung” wird im Rahmen eines mehrj?hrigen Arbeitsplanes in vier Programmphasen abgewickelt. Die erste und methodisch wichtigste Programmphase soll Ende n?chsten Jahres mit dem Billigungsvorschlag einer Pilotmethode an den Rat zwecks sukzessiver Erfassung des gesamten Gebiets der EG abgeschlossen werden.

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The prevention of future environmental damage. The European Community is stimulating the development of instruments for a preventive environmental policy

Summary Under the influence of the magnitude of the conflicting influences to which the environmental system is exposed, the recognition that the best environmental policy consists in the prevention as far as possible from the very beginning of environmental pollution, rather than in dealing with its effects after the event, has become the most important basic principle of environmental policy, including the Community's Action Programme. The practical implementation of this principle of preventive environmental planning does, however, depend on the availability of sufficient suitable information on the state and characteristics of the environment and on there existing a mechanism by which this information can be fed into the decision-making process. These preconditions are not usually fulfilled at the present time. The two actions in the fields of “Environmental Impact Assessment” and “Ecological Mapping” represent the main thrust of the Community's efforts to play a catalytic role in this field. The actions are complementary in several respects. It is expected that the Commission will present its first proposals to the EC Council of Ministers on “Environmental Impact Assessment” in the course of the coming year. The “Ecological Mapping” is being developed in a multi-annual work programme, divided into four phases. The first, and methodologically most important phase should end next year with a proposal to the Council to approve a pilot methodology which can be used for the gradual mapping of all Community territory.

     

Gruppenverteidigungsverhalten bei wildlebenden Bienen (Apis cerana Fabr.) in Afghanistan

Ohne Zusammenfassung     

Aussetzung vonAphidecta obliterata L. (Coccinellidae) auf der Nordseeinsel Amrum zur biologischen Kontrolle der Sitkalaus (Liosomaphis abietina Walk.Aphididae)

Ohne Zusammenfassung     

Wood-polymer combinations: Bonding of alkoxysilane coupling agents to wood

Summary Trembling aspen has been impregnated with the coupling agent -methacryloxypropyltrimethoxysilane and the hygroscopicity and antishrink efficiency measured before and after water extraction. There was a hygroscopicity depression with treatment, but not enough to account for the observed antishrink efficiencies. There was limited reversibility after water extraction. This indicated that the wood was interacting with part of the sorbed silane more strongly than with water, and that there was a diversity of sorption environments within the wood-silane complex.The authors are grateful for financial support by the Natural Sciences and Engineering Research Council of Canada     

Hygroscopicity of wood impregnated with linseed oil

Summary The reduction in hygroscopicity as spruce wood is impregnated with linseed oil may be accounted for using a molecular exclusion model. On the basis of the model, each linseed oil molecule appears to displace 90 water molecules and occupy 6 hydrogen bonding sites in the wood.Dr. Allen R. Sharp, Associate Professor of Physics at the University of New Brunswick and Dr. Christen Skaar, Professor of Wood Physics at Virginia Polytechnic Institute and State University freely gave essential advice and encouragement during this work. Graphical depiction of the molecular displacement model (Fig. 1) was suggested by Dr. Skaar. Much of the experimental work was carried out by Mr. Wu-Rong Perng, Scientific Technician in Wood Science and Mrs. Monica Snow, Instructor in Wood Science at the University of New Brunswick