Host-seeking behaviour of tracheal mites (Acari: Tarsonemidae) on honey bees (Hymenoptera: Apidae)

The behaviour of the endoparasitic tracheal mite, Acarapis woodi (Rennie) on honey bees (Apis mellifera L.) is a challenge to observe because of its small size. Through a microscope, we videotaped this mite's movement on young bees, dead bees and bees exposed to vegetable oil. Previous studies have shown that solid vegetable oil decreases mite infestations in a bee colony. We hypothesized that the oil alters mite behaviour to the detriment of the parasite, thus helping to safeguard the host. Habitat-seeking behaviour, identified as necessary for mites to locate a new host environment, was disrupted on both dead and oil-treated bees. Questing behaviour, which is associated with transfer between hosts, increased significantly on the dead and oily bees. The behaviours of mites were significantly different between all three treatments (x ²=494.96, p<0.001 on dead bees and x ²=851.11, p<0.001 on oily bees). Both questing and seeking behaviours were significantly different on each of the thoracic treatments (F _2,66=7.88, p<0.001 and F _2,66=21.28, p<0.001) and mite questing behaviour was not altered between males and females on live or oily bees (F _1,22=0.25, p<0.62), but habitat seeking was (F _1,22=7.42, p<0.012). The male questing and habitat-seeking behaviours were observed. We conclude that oil-treated bees gained protection from habitat-seeking mites because the normal behaviour of the mites seeking an oviposition site is interrupted.     

Affinities of Shiga toxins 1 and 2 for univalent and oligovalent Pk-trisaccharide analogs measured by electrospray ionization mass spectrometry

The binding stoichiometry and affinities of the Shiga toxins, Stx1 and Stx2, for a series of uni- and oligovalent analogs of the Pk-trisaccharide were measured using the direct electrospray ionization mass spectrometry (ES-MS) assay. Importantly, it is shown that, for a given ligand, Stx1 and Stx2 exhibit similar affinities. The binding data suggest a high degree of similarity in the spatial arrangement and structural characteristics of the Pk binding sites in Stx1 and Stx2. The results confirm that both toxins recognize the alpha-D-Galp(1-->4)-beta-D-Galp(1-->4)-beta-D-Glcp carbohydrate motif of the cell surface glycolipid Gb3. This, taken together with the results of the chemical mapping study, suggests that the nature of the Pk binding interactions with Stx1 and Stx2 are similar. The affinities of Stx1-B(5) and Stx2 for the multivalent ligands reveals that site 2 of Stx2, which shares the same spatial arrangement as site 2 in Stx1, is the primary Pk binding site and that site 1 of Stx1 and of Stx2 can also participate in Pk binding.     

Molecular detection of predation by soil micro-arthropods on nematodes

The relative importance of the factors driving change in the population dynamics of nematodes in the soil is almost completely unknown. Top-down control by micro-arthropod predators may have a significant impact on nematode population dynamics. We report experiments showing that mites and Collembola were capable of reducing nematode numbers in the laboratory and were feeding on a targeted nematode species in the field. A PCR-based approach was developed for the detection of predation on three species of slug- and insect-pathogenic nematodes: Phasmarhabditis hermaphrodita, Heterorhabditis megidis and Steinernema feltiae. The collembolan Folsomia candida and the mesostigmatid mite Stratiolaelaps miles were employed as model predators to calibrate post-ingestion prey DNA detection times. Fragments of cytochrome oxidase I (COI) mtDNA were sequenced and species-specific primers were designed, amplifying 154-, 154- and 203-bp fragments for each of the nematode species. Detection times for nematode DNA within the guts of Collembola were longer than in mites, with half-lives (50% of samples testing positive) of 08.75 h and 05.03 h, respectively. F. candida significantly reduced numbers of the nematode H. megidis, with rates of predation of approximately 0.4 nematode infective juveniles per collembolan per hour over 10 h. Four taxa of field-caught micro-arthropod that had been exposed to the nematode P. hermaphrodita for a period of 12 h were analysed and significant numbers of three taxa tested positive. This is the first application of PCR techniques for the study of nematophagy and the first time these techniques have been used to measure predation on nematodes in the field.     

Fostering Community-Based Wildlife Health Monitoring and Research in the Canadian North

Many northern Canadians have continued a subsistence lifestyle of wildlife harvesting and, therefore, value sustainable wildlife populations. At a regional wildlife workshop in the Sahtu Settlement Area, Northwest Territories in 2002, elders and community leaders raised concerns regarding wildlife health, food safety, and the effects of climate change on wildlife. They requested that efforts be put toward training youth in science and increasing involvement of hunters and youth in wildlife research. In response, we initiated a long-term, integrated approach to foster community-based wildlife health monitoring and research. Annual trips were made to all schools in the Sahtu from 2003 to 2009 to provide hands-on learning for 250–460 students on a range of wildlife topics. In addition, interviews were conducted with 31 hunters and elders to document their local ecological knowledge of wildlife health and local hunters were trained as monitors to collect tissue samples and measurements to assess body condition and monitor health of harvested caribou (n = 69) and moose (n = 19). In 2007 the program was extended to include participation in the annual caribou hunt held by one community. Each year since 2005, a graduate student and/or a postdoctoral trainee in the veterinary or biological sciences has participated in the program. The program has evolved during the last 6 years in response to community and school input, results of empirical research, hunter feedback, local knowledge, and logistical constraints. The continuity of the program is attributed to the energetic collaboration among diverse partners and a unified approach that responds to identified needs.     

Robust testing of haplotype/disease association

Haplotypes, the combination of closely linked alleles that fall on the same chromosome, show great promise for studying the genetic components of complex diseases. However, when only multilocus genotype data are available, statistical approaches need to be employed to resolve haplotype phase ambiguity. Recently, we have proposed an approach to testing and estimating haplotype/disease association that is invariant to any existing genetic structure in the population. Here we evaluate this approach by applying it to the Genetic Analysis Workshop 14 simulated data.     

Diurnal variation in heart rate variability before and after maximal exercise testing

As heart-rate variability (HRV) is under evaluation in clinical applications, the authors sought to better define the interdependent impact of age, maximal exercise, and diurnal variation under physiologic conditions. The authors evaluated the diurnal changes in HRV 24-h pre- and post-maximal aerobic exercise testing to exhaustion in young (19-25 yrs, n?=?12) and middle-aged (40-55 yrs, n?=?12) adults. Subjects wore a portable 5-lead electrocardiogram holter for 48?h (24?h prior to and following a maximal aerobic capacity test). Time-, frequency-, time-frequency-, and scale-invariant-domain measures of HRV were computed from RR-interval data analyzed using a 5-min window size and a 2.5-min step size, resulting in a different set of outputs every 2.5?min. Results were averaged (mean?±?SE) over four prespecified time periods during the morning, afternoon, evening, and night on Day 1 and Day 2. Diurnal changes in HRV in young and middle-aged adults were compared using a two-way, repeated-measures analysis of variance (ANOVA). Young adults demonstrated higher HRV compared to middle-aged adults during periods of wakefulness and sleep prior to maximal exercise stress testing (i.e., high-frequency power during Day 1: young adults: morning 1862?±?496?ms(2), afternoon 1797?±?384?ms(2), evening 1908?±?431?ms(2), and night 3202?±?728?ms(2); middle-aged adults: morning 341?±?53?ms(2), afternoon 405?±?68?ms(2), evening 469?±?80?ms(2), and night 836?±?136?ms(2)) (p < .05). Exercise resulted in reductions in HRV such that multiple measures of HRV were not significantly different between age groups during the afternoon and evening periods. All measures of HRV demonstrated between-group differences overnight on Day 2 (p < .05). Young adults are associated with higher baseline HRV during the daytime. Sleep increases variability equally and proportionally to daytime variability. Given the higher baseline awake HRV and equal rise in HRV during sleep, the change in HRV from sleep to morning with exercise is greater in younger subjects. These physiologic results have clinical significance in understanding the pathophysiology of altered variability in ill patients.     

Light enhanced amino acid uptake by dominant bacterioplankton groups in surface waters of the Atlantic Ocean

(35)S-Methionine and (3)H-leucine bioassay tracer experiments were conducted on two meridional transatlantic cruises to assess whether dominant planktonic microorganisms use visible sunlight to enhance uptake of these organic molecules at ambient concentrations. The two numerically dominant groups of oceanic bacterioplankton were Prochlorococcus cyanobacteria and bacteria with low nucleic acid (LNA) content, comprising 60% SAR11-related cells. The results of flow cytometric sorting of labelled bacterioplankton cells showed that when incubated in the light, Prochlorococcus and LNA bacteria increased their uptake of amino acids on average by 50% and 23%, respectively, compared with those incubated in the dark. Amino acid uptake of Synechococcus cyanobacteria was also enhanced by visible light, but bacteria with high nucleic acid content showed no light stimulation. Additionally, differential uptake of the two amino acids by the Prochlorococcus and LNA cells was observed. The populations of these two types of cells on average completely accounted for the determined 22% light enhancement of amino acid uptake by the total bacterioplankton community, suggesting a plausible way of harnessing light energy for selectively transporting scarce nutrients that could explain the numerical dominance of these groups in situ.