261 Bisamratten im Aalfang

Ohne Zusammenfassung     

Ungewöhnliche Schäden durch Holzwespen (Siricidae,Hym.)

Ohne Zusammenfassung     

Versuche zur Bekämpfung der Hausratten mit Streupulver

Zusammenfassung 1. Das Streupulver (Delicia-Ratron-Streupulver) hat sich bis jetzt als ein recht brauchbares Hausrattenmittel gezeigt. wenn es in Verbindung mit geeigneten Ködern den Hausratten einverleibt werden kann.Eine Pulver- oder Köderscheu besteht nicht, dagegen kann von einer anlockenden Wirkung gesprochen werden. Die wiederholte Annahme anderer Giftköder durch Hausratten ist bekannt, diese Köder finden noch bessere Annahme. Bei der Auslage von Brotscheiben kann die unangenehme Verschmutzung der Auslegestelle durch das Pulver durch ein loses Einwickeln der Scheiben in Zeitungspapier verhütet werden.2. Der Zeitpunkt für die Anlage von Schüttungen war günstig. Von Anfang Oktober bis Ende März des nächsten Jahres haben die Hausratten die Winterquartiere bezogen. Ein gewisser, aber nicht durchschlagender Erfolg kann diesen Schüttungen zugesprochen werden, doch steht der Erfolg in keinem Verhältnis zum Aufwand an Material und Arbeitszeit.3. Die Ursache des angeblich gesteigerten Lärmes in den Einschüben der Zimmerdecken bedarf noch der Klärung.4. Das Streupulver war für mich ein neues Rattenmittel, dessen Anwendung und Wirkungsbreite ich durch eigene Versuche kennen lernen wollte. Eine solche Versuchsreihe, die Anlage von Schüttungen, die Suche nach geeignetem Ködermaterial konnte recht gut, im Zuge der pausenlosen Schädlingsbekämpfung, die hier eingeführt ist, erfolgen.     

Monitoring the gravitational reflex of the ectoparasitic mite Varroa destructor: A novel bioassay for assessing toxic effects of acaricides

We investigated the effect of several acaricides on Varroa destructor by monitoring the rhythmic expansion of the sternum, followed by a strong flexion of the legs, initiated when the mite was placed in a dorsal side-down position, as an indication of a mite’s vitality. The pulses generated by the force of the rhythmic expansions had an average duration of 3.11 s, force (amplitude) of 73 μN, and frequency of 0.228 Hz. These parameters remained constant for the first 10 h of recording, whilst significant changes occurred after 15 h. The rhythmic sternal expansion is an indication of a Varroa mite’s gravitational reflex, or attempt to return to an upright position; this reflex is observed in all invertebrates and vertebrates. The sternal expansion can be recorded for over 20 h, or for as long as the Varroa mite remains alive, and the expansion stops as soon as the mite is placed in a normal, upright position. Proper function of the chain of proprioceptors, interneurons, motorneurons, neuromuscular junctions, and muscles of Varroa is required for the initiation and maintenance of such a behavioural motor pattern. Any deleterious effect of synthetic chemicals or natural compounds (acaricides) may have a direct effect on one or more of these links, thereby disturbing or even inhibiting the reflex. Topical application of 1.81 × 10⁻³ mg/mite of amitraz completely inhibited the gravitational reflex within 60–70 min for all mites tested. The volatile acaricides formic acid (13.83 mg), thymol crystals (250 mg), and Apiguard® (1000 mg) eliminated the reflex within 10–35 min. This bioassay, based on the gravitational reflex, could be a useful tool for accurate assessment of the acaricidal action of numerous compounds under laboratory conditions, saving money and time necessary to conduct field trials.     

Genetics of colour traits in common vetch (Vicia sativa L.)

Five parents of common vetch (Vicia sativa L.) having orange/beige cotyledon colour, brown/white testa colour, purple/green seedling colour and purple/white flower colour were crossed as a full diallele set. The inheritance patterns of cotyledon, testa or seed coat colour, flower and seedling colour, were studied by analyzing their F₁, F₂, BC₁ and BC₂ generations. The segregation pattern in F₂, BC₁ and BC₂, showed that cotyledon colour was governed by a single gene with incomplete dominance and it is proposed that cotyledon colour is controlled by two allelic genes, which have been designated Ct₁ and Ct₂. Testa colour was governed by a single gene with the brown allele dominant and the recessive allele white. This gene has been given the symbol H. Two complementary genes governed both flower and seedling colours. These flower and seedling colour genes are pleiotropic and the two genes have been given the symbols S and F.     

Carbon stable isotope fractionation and trophic transfer of fatty acids in fungal based soil food chains

Stable isotope analysis has been used as a powerful tool in food web studies in terrestrial ecosystems. In addition the occurrence and abundance of fatty acids may serve as indicator for feeding strategies of soil animals. Here we combine both approaches and investigate the fatty acid composition, δ¹³C values of bulk tissues and individual fatty acids in soil organisms. The fungi Chaetomium globosum and Cladosporium cladosporioides were isotopically labelled by fructose derived from either C₃ or C₄ plants, and the fungal-feeding nematode Aphelenchoides sp. was reared on C. globosum. Fungi and nematodes were used as diet for the Collembolan Protaphorura fimata. The sugar source was fractionated differently by fungal lipid metabolism in a species-specific manner that points to a sensitivity of physiological processing to the non-random distribution of ¹³C/¹²C isotopes in the molecule. As a general trend stearic acid (18:0) was depleted in ¹³C compared to the precursor palmitic acid (16:0), whereas its desaturation to oleic acid (18:1 ω9) favoured the ¹³C-rich substrate.Fatty acid profiles of P. fimata varied due to food source, indicating incorporation of dietary fatty acids into Collembolan tissue. Individuals feeding on fungi had lower amounts in C20 fatty acids, with monoenoic C20 forms not present. This pattern likely separates primary consumers (fungivores) from predators (nematode feeders). The isotopic discrimination in ¹³C for bulk Collembola ranged between −2.6 and 1.4‰ and was dependent on fungal species and C₃/C₄ system, suggesting differences at metabolic branch points and/or isotope discrimination of enzymes. Comparison of δ¹³C values in individual fatty acids between consumer and diet generally showed depletion (i.e. de novo synthesis) or no changes (i.e. dietary routing), but the fractionation was not uniform and affected by the type of ingested food. Fatty acid carbon isotopes were more variable than those of bulk tissues, likely due to both the distrimination by enzymes and the different lipid origin (i.e. neutral or polar fraction).