Recording the activity of animals as they migrate or forage has proven hugely advantageous to understanding how animals use
their environment. Where animals cannot be directly observed, the problem remains of how to identify distinct behaviours that
represent an animal’s decision-making process. An excellent example of this problem is that of foraging penguins, which travel
to sea to find prey to provision their young. Without direct sampling of the prey field, we cannot calibrate patterns of movement
with prey capture, and therefore we cannot determine how different activities link to decision-making. To overcome this, we
use a hidden markov model (HMM), which is a machine-learning technique that seeks to identify the underlying states of a system
from observable outputs. We apply HMM to determine classes of behaviour from repetitive dives. We take dive data from 103
breeding macaroni penguins at Bird Island, South Georgia, for which we have measures of weight gain over a trip. We identify
two classes of behaviour; those of short-shallow and long-deep dives. Using these two behaviours, we calculate the transition
probabilities between these states and analyse these data to determine what predicts variation in the transition probabilities.
We found that the stage of reproduction during a season, the sex and year of an individual influenced the probability of transition
between long-deep and short-shallow sequential dives. We also found differences in the hourly transition rates between the
four reproductive stages (incubation, broodguard, crèche and premoult) over a daily cycle. We conclude that this application
of HMMs for behavioural switching is potentially useful for other species and other types of recorded behaviour. 相似文献
Ambient concentrations, congener patterns and multi-media distribution of PCDD/Fs and PCBs were determined in air, water, sediment and mussels in a semi-enclosed marine ecosystem (Thau lagoon, France). summation operator2,3,7,8-PCDD/F and summation operator7ICES PCB air concentrations (0.2-1.4 and 31-57pg m(-3), respectively) were typical of rural areas. Concentrations in the water column were very low for PCDD/Fs (163-476fg L(-1)) and low for PCBs (138-708pg L(-1)). PCDD/F and PCB concentrations found in surface sediment (0.15-1.6 and 2.5-33ng g(-1) d.w., respectively) and mussel (13-21pg g(-1) d.w. and 10-39ng g(-1) d.w., respectively) were medium levels. PCDD/F congener patterns observed in air, water particulate phase and sediments were similar suggesting direct coupling among these compartments and atmospheric inputs of PCDD/Fs into the lagoon. Conversely, for the same set of samples, similar patterns were not observed for PCBs in the mentioned compartments. 相似文献
Infection with the hepatitis E virus (HEV) is very common worldwide. HEV causes acute viral hepatitis with approximately 20 million cases per year. While HEV genotypes 1 and 2 cause large waterborne and foodborne outbreaks with a significant mortality in developing countries, genotypes 3 and 4 are more prevalent in developed countries with transmission being mostly zoonotic. In North America and Europe, HEV has been increasingly detected in swine, and exposure to pigs and pork products is considered to be the primary source of infection. Therefore we set out to investigate the prevalence of HEV in retail pork products available in Canada, by screening meal-size portions of pork pâtés, raw pork sausages, and raw pork livers. The presence of the HEV genomes was determined by RT-PCR and viral RNA was quantified by digital droplet PCR. Overall, HEV was detected in 47% of the sampled pork pâtés and 10.5% of the sampled raw pork livers, but not in the sampled pork sausages, and sequencing confirmed that all HEV strains belonged to genotype 3. Further phylogenetic analysis revealed that except for one isolate that clusters with subtype 3d, all isolates belong to subtype 3a. Amino acid variations between the isolates were also observed in the sequenced capsid region. In conclusion, the prevalence of HEV in pâtés and raw pork livers observed in this study is in agreement with the current HEV distribution in pork products reported in other developed countries. 相似文献
The reconstruction of past climates is a major challenge. One approach is the use of paleoceanography, which looks for clues
to the past activity of deep-sea currents by associating them with the melting of the poles. In different sampling zones,
fossil biomarkers are used to reconstruct the oxygenation levels of the sea bottom. Among the ostracods (crustaceans), the
family Cytherellidae is considered to be resistant to significant decreases in oxygen and their fossil valves are used as
biomarkers for oxygenation levels in the past. We studied the basic principles behind Cytherella cf. abyssorum’s ability to adapt to variations in water oxygenation levels in an attempt to determine what could differentiate it from
other ostracods. Cytherella cf. abyssorum Sars 1866 has an activity level and ventilatory frequency only half that of ostracods studied previously. When subjected
to a decrease in oxygenation, it demonstrates the beginnings of ventilatory adaptation which is unknown in the other studied
ostracods. Some morpho-functional aspects are also remarkable, such as the presence of thick valves, which can close hermetically
by means of powerful adductor muscles. Compared with already studied ostracods, Cytherella cf. abyssorum has, therefore, characteristics which suggest an ability to present increased resistance in hypoxia. We discuss these results
in the paleoceanographical context by describing a scenario suggesting why an increased proportion of the ostracod population
could indicate the existence of ocean bottoms with low oxygenation. 相似文献
Whether general environmental exposures to endocrine disrupting chemicals (including pesticides and dioxin) might induce decreased
sex ratios (male/female ratio at birth) is discussed. To address this issue, the authors looked for a space-time clustering
test which could detect local areas of significantly low risk, assuming a Bernoulli distribution. As a matter of fact, if the endocrine disruptor hypothesis holds true, and if the
sex ratio is a sentinel health event indicative of new reproductive hazards ascribed to environmental factors, then in a given
region, either a cluster of low male/female ratio among newborn babies would be expected in the vicinity of polluting municipal
solid waste incinerators (MSWIs) (supporting the dioxin hypothesis), or local clusters would be expected in some rural areas
where large amounts of pesticides are sprayed.
Among cluster detection tests, the spatial scan statistic has been widely used in various applications to scan for areas
with high rates, and rarely (if ever) with low rates. Therefore, the goal of this paper was to check the properties of the
scan statistics under a given scenario (Bernoulli distribution, search for clusters with low rates) and to assess its added
value in addressing the sex ratio issue.
This study took place in the Franche-Comté region (France), mainly rural, comprising three main MSWIs, among which only one
had high dioxin emissions level in the past. The study population consisted of 192,490 boys and 182,588 girls born during
the 1975–1999 period.
On the whole, the authors conclude that: (i) spatial and space-time scan statistics provide attractive features to address
the sex ratio issue; (ii) sex ratio is not markedly affected across space and does not provide a reliable screening measure
for detecting reproductive hazards ascribed to environmental factors. 相似文献
In the context of urban agriculture, where soils are frequently contaminated with metal(loid)s (TM), we studied the influence of vermicompost amendments on symbiotic fungal communities associated with plants grown in two metal-rich soils. Leek (Allium porrum L.) plants were grown with or without vermicompost in two metal-rich soils characterized by either geogenic or anthropogenic TM sources, to assess the influence of pollutant origin on soil-plant transfer. Fungal communities associated with the leek roots were identified by high throughput Illumina MiSeq and TM contents were measured using mass spectrometry. Vermicompost addition led to a dramatic change in the fungal community with a loss of diversity in the two tested soils. This effect could partially explain the changes in metal transfer at the soil-AMF-plant interface. Our results suggest being careful while using composts when growing edibles in contaminated soils. More generally, this study highlights the need for further research in the field of fungal communities to refine practical recommendations to gardeners.
The potential sources of relatively great concentrations of arsenic (As) in oysters from the Southeastern United States coast was examined in a study conducted from August 1998 through October 1999. A transplant experiment was conducted to determine whether genetic or environmental differences accounted for the observed difference between Southeastern oysters, and oysters elsewhere on the east coast. Oysters originating in South Carolina (a region where As in oysters is usually greater) and Maryland (a region where arsenic is oysters is less) were reciprocally transplanted to determine whether site of growth or site of origin would determine the accumulation of As. To examine the potential role of various potential sources of As exposure on the concentrations of As in oysters, samples of native oysters, water, pore water and suspended particles were collected and analyzed for As monthly, while the sediments were examined four times during the year. Concentrations of As in transplanted oysters matched the concentrations of As in oysters native to the area in which they were grown, rather than that of oysters from their site of origin. Oysters from South Carolina had average concentrations of As approximately 3.2 times that of oysters from Maryland. This enrichment was similar to enrichments of water (3.4 times), sediment (2.5 times), suspended particles (1.7 times), and pore water (3.1 times) from South Carolina compared to Maryland. This supports the hypothesis that the cause of the apparent As enrichments in the Southeastern oysters is environmental, but leaves the question of the primary source for arsenic incorporation by oysters open. 相似文献