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.     

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).     

Die Einführung der Arsenverstäubung vom Flugzeug aus in die Praxis der Forstschädlingsbekämpfung

Ohne Zusammenfassung     

Summer pruning effects in apple — a review

Summer pruning effects in apple have generally been attributed to improved light penetration and to reduced carbohydrate supply. However, the common basis to most of these effects seems to be the retardation of senescence, a process under hormonal control. Summer pruning causes a temporary loss of apical dominance except when thinning cuts are used. It also causes a temporary increase in cytokinin supply, presumably mainly by increased export from the roots. Both effects presumably result from reduced auxin availability.

Depending on its timing, the resulting rejuvenation may consist of mobilization and redistribution of nutrients and phytohormones, breaking of axillary buds, inhibition of flower induction, delayed fruit development and later induction of dormancy. The extent of pruning responses increases with the vigour of the tree, the earliness of pruning and its severity. Heading and stubbing are more effective in provoking these responses than thinning of shoots. In areas with a short season, summer pruning may not only delay, but also prevent, the onset of dormancy, with adverse effects on winter hardiness. The mostly positive influence of summer pruning on fruit colour by factors in addition to better light penetration is discussed. Summer pruning, where considered necessary, needs to be adjusted to local conditions and coordinated with other cultural practices.     

The bovine innate immune response during experimentally-induced Pseudomonas aeruginosa mastitis

Almost half of all clinical cases of mastitis are caused by Gram-negative bacteria. Among these bacteria, intramammary infection by Pseudomonas aeruginosa remains one of the most refractory to antibiotic therapy. The ability to recognize potentially harmful pathogens whether previously encountered or not, as well as the induction of an initial pro-inflammatory response to these pathogens, are critical components of host innate immunity. Although the innate immune response to another Gram-negative mastitis-causing pathogen, Escherichia coli, has been well-characterized, little is known about the response to other Gram-negative bacteria, including P. aeruginosa. The objective of the current study was to characterize the systemic and localized bovine innate immune response to intramammary infection with P. aeruginosa. The contralateral quarters of ten mid-lactating Holstein cows were challenged with either saline or P. aeruginosa. Following the establishment of infection, milk samples were collected and assayed for changes in cytokine and growth factor concentrations, complement activation, and changes in the levels of soluble CD14 (sCD14) and lipopolysaccharide (LPS)-binding protein (LBP), two accessory molecules involved in host recognition of Gram-negative bacteria. Initial increases in milk somatic cell counts were evident within 12h of experimental challenge and remained elevated for >or=3 weeks. Increased permeability of the mammary gland vasculature, as evidenced by elevated milk levels of BSA, was initially observed 20 h post-infection and persisted for 2 weeks. Within 32 h of challenge, increased levels of IL-8, TNF-alpha, IL-10, and IL-12 were detected, however, the elevated levels of these cytokines were not sustained for longer than a 24h period. In contrast, elevations in IL-1beta, IFN-gamma, TGF-alpha, TGF-beta1, TGF-beta2, sCD14, LBP, and activated complement factor 5 (C5a) were sustained for periods of >48 h. Systemic changes were characterized by elevated body temperature, induction of the acute phase protein synthesis of serum amyloid A and LBP, and a transient decrease in circulating neutrophils and lymphocytes. Together, these data demonstrate the capability of the mammary gland to mount a robust innate immune response to P. aeruginosa that is characterized by the induction of pro-inflammatory cytokines, complement activation, and increased levels of accessory molecules involved in Gram-negative bacterial recognition.     

The application of sexual coral recruits for the sustainable management of ex situ populations in public aquariums to promote coral reef conservation — SECORE Project

• 1. SECORE (SExual COral REproduction) Project is an initiative of public aquariums and research institutions to produce and exchange sexual coral recruits for the sustainable management of ex situ populations. Here we present the results of the initial three years (2002–2004).
• 2. Primary polyps (n=501) of corals (Acropora tenuis, Agaricia humilis, Favia fragum) were transported from Rotterdam Zoo to Cologne, Burgers', Hagenbeck and London Zoos, where development of juveniles was monitored for 10 months. All polyps were produced at Rotterdam Zoo from laboratory colonies (A. humilis, F. fragum), and from larvae generated from field collected gametes at Akajima, Okinawa, Japan (A. tenuis). Additionally, planulae of A. tenuis (n=1440) were transported from Rotterdam Zoo to Burgers' Zoo and to London Zoo to obtain primary polyps.
• 3. Larval settlement (A. tenuis) was observed to be 3.00 ± 2.57% (mean ± SD; n=1480) in 2002 and 17.36 ± 6.01% (mean ± SD; n=1480) in 2003, significantly lower compared to settlement at Rotterdam Zoo (57.84 ± 11.01% in 2003; mean ± SD, n=1480). High post‐transport survival rates of 95.18 ± 4.86% (mean ± SD; n=501) were observed in primary polyps of all species.
• 4. Juvenile survival (t=10 months; A. tenuis: 18.4–86.2%; A. humilis: 0–19.7%; F. fragum: 13.3–72.7%) differed significantly between institutions. Mean colony sizes (measured 10 months after transportation) were, in all cases, similar or higher to those reported from literature.
• 5. The results demonstrate the potential of this method to serve as an economical and sustainable alternative to existing mostly exploitative techniques for aquarium stocking. The use of sexual recruits provides an effective and low cost alternative, which is, in principle, applicable to all coral species.
• 6. The project was extended from 9 to 28 institutions across Europe, the USA and Japan in 2004.

Copyright © 2006 John Wiley & Sons, Ltd.