A unified evolutionary framework for understanding parasite infection and host migratory behaviour.

Animal migration impacts organismal health and parasite transmission: migrants are simultaneously exposed to parasites and able to reduce infection for both individuals and populations. However, these dynamics are difficult to study; empirical studies reveal disparate results while existing theory makes assumptions that simplify natural complexity. Here, we systematically review empirical studies of migration and infection across taxa, highlighting key gaps in our understanding. Next, we develop a unified evolutionary framework incorporating different selective pressures of parasite-migration interactions while accounting for ecological complexity that goes beyond previous theory. Our framework generates diverse migration-infection patterns paralleling those seen in empirical systems, including partial and differential migration. Finally, we generate predictions about which mechanisms dominate which empirical systems to guide future studies. Our framework provides an overarching understanding of selective pressures shaping migration patterns in the context of animal health and disease, which is critical for predicting how environmental change may threaten migration.

ß-Hydroxybutyrate impairs neutrophil migration distance through activation of a protein kinase C and myosin light chain 2 signaling pathway in ketotic cows.

Ketosis in dairy cows often occurs in the peripartal period and is accompanied by immune dysfunction. High concentrations of ß-hydroxybutyrate (BHB) in peripheral blood during ketosis are closely related to the impairment of polymorphonuclear neutrophil (PMN) chemotaxis and contribute to immune dysfunction. The specific effect of BHB on PMN chemotaxis in dairy cows and the underlying molecular mechanisms are unclear. Here, 30 multiparous cows (within 3 wk postpartum) classified based on serum BHB as control (n = 15, BHB <0.6 mM) or clinically ketotic (n = 15, BHB >3.0 mM) were used. Blood samples were collected before feeding, and the isolated PMN were treated with platelet-activating factor for 0.5 h to activate their migration. Scanning electron microscopy revealed a longer tail in PMN of ketotic cows. In addition, the phosphorylation and transcription levels of myosin light chain 2 (MLC2) increased in PMN of ketotic cows. Polymorphonuclear neutrophils from control dairy cows were incubated with 3.0 mM BHB for different times in vitro, and 6 h was selected as the proper duration of BHB stimulation according to its inhibition effect on PMN migration using an under-agarose PMN chemotaxis model. Similarly, BHB stimulation in vitro resulted in inhibition of migration distance and deviation of migration direction of PMN, as well as a longer tail in morphology in the scanning electron microscope data, suggesting that BHB-induced PMN migration inhibition may be mediated by impairing the trailing edge contraction. To confirm this hypothesis, sotrastaurin (Sotra)-a specific inhibitor of protein kinase C (PKC), which is the core regulator of cell contraction-was used with or without BHB treatment in vitro. Sotra was pretreated 0.5 h before BHB treatment. Accordingly, BHB treatment increased the phosphorylation level of PKC and MLC2, the protein abundance of RhoA and rho-kinase 1 (ROCK1), and the mRNA abundance of PRKCA, MYL2, RHOA, and ROCK1 in PMN. In contrast, these effects of BHB on PMN were dampened by Sotra. As demonstrated by immunofluorescence experiments in vitro, the BHB-induced inhibition of trailing edge contraction of PMN was relieved by Sotra. In addition, Sotra also dampened the effects of BHB on PMN migration in vitro. Furthermore, as verified by in vivo experiments, compared with the control cows, both abundance and activation of PKC signaling were enhanced in PMN of ketotic cows. Overall, the present study revealed that high concentrations of blood BHB impaired PMN migration distance through inhibition of the trailing edge contraction, mediated by enhancing the activation of PKC-MLC2 signaling. These findings help explain the dysfunctional immune state in ketotic cows and provide information on the pathogenesis of infectious diseases secondary to ketosis.

The avian lightweights: Trans-Saharan migrants show lower lean body mass than short-/medium-distance migrants.

Avian trans-Saharan migrants travelling long distances and crossing ecological barriers experience different constraints in terms of time, energy and safety than short-/medium-distance migrants without barrier-crossings. As such, natural selection shapes the aerodynamic properties of these groups differently. Yet, to the best of our knowledge, we lack information on whether natural selection has contributed to reducing energetic flight costs through generally lower body mass in trans-Saharan migrants. To fill parts of this gap, we investigated this eco-morphological pattern in 5,410 individuals of 22 Palearctic songbird species ranging from short-/medium-distance to trans-Saharan migrants. We used individual size-independent scaled lean body mass values based on wing length as a measure of body size and, for the first time, precisely determined lean body mass values by direct measurements via quantitative magnetic resonance technology. Scaled lean body mass for a given body size was significantly higher in short-/medium-distance migrants than in trans-Saharan migrants. Although scaled lean body mass significantly decreased with increasing migration distance in short-/medium-distance migrants, no such effect was found in trans-Saharan migrants. Our results thus show an eco-morphological pattern relating species' lean body mass not only to migration distance but also to migration group. This suggests that selective effects of the presence/absence of ecological barriers and/or of a threshold level for migration distance on migrant birds may be more important than the linear continuum of migration distance per se.

Employment, education, and family: Revealing the motives behind internal migration in Great Britain.

Distinctions between internal migration and residential mobility are often formed with reference to assumed differences in motivation, with migration typically linked to employment and educational motives and shorter distance mobility to housing and family. Using geocoded microdata, this article reveals how employment-led migration represents only a minority share (≈30%) of total migration events over 40 km. Family motives appear just as important, even at distances ≥100 km, with the desire to live closer to non-resident family/friends being the most frequently cited family submotive. Estimated propensities to undertake employment and educational-related migration fit very closely to predictions of human capital models of migration, being highest among young, residentially flexible and highly educated individuals. Migrants citing family-related motives are disproportionately drawn from midlife and later-life phases, with family shown to be a key motive among migrants with care-related needs (e.g., parents with children) or access to fewer resources (e.g., social renters and low educational attainment).

Is the duration of the smolt window related to migration distance in coho salmon Oncorhynchus kisutch?

Physiological changes during the parr-smolt transformation were investigated in short distance (Chilliwack River) and long-distance (Salmon River) migrating coho salmon Oncorhynchus kisutch populations in British Columbia, Canada. Biochemical and molecular indicators were used to monitor smolt development for fish reared at 10 °C throughout the spring. Fish grew well and developed the physical appearance of competent smolts. Both populations exhibited increases in gill Na+ -K+ -ATPase activity (NKA; an important indicator of seawater tolerance) at the same date and the duration of the increase in enzyme activity did not differ between populations. Gill messenger (m)RNA copies for two isoforms of the NKA α subunit, α1a and α1b, showed significant changes and the pattern was similar between populations. Growth hormone receptor and prolactin receptor mRNA from the gill showed modest changes associated with smolting in the spring for both populations, suggesting that these may not be useful indicators of smolt development in hatchery-reared O. kisutch. Consequently, the duration of the smolt window was not based on the region of origin in the present study.

[Correlation between Movement Distance of Small Intestinal Contents and Survival Time in Female Rats after Feeding].

OBJECTIVES: To study the correlation between the movement distance of small intestinal contents and survival time in female SD rat models after one-time satiation, and to evaluate its application value for postmortem interval estimation. METHODS: Adult female SD rats were randomly divided into postprandial groups （1, 2, 3, 4 and 5 h after feeding） and control group. The postprandial groups were fed for 1 h, meanwhile control group was kept fasting. All rats were sacrificed at the given time. The contents in stomach and small intestine were observed, described, compared and photographed, and the movement distance of small intestinal contents was measured. The data of postprandial groups were analysed by one-way analysis of variance. RESULTS: The stomach and duodenum of control group were empty with a little thin and yellow small intestinal liquid. The gastral cavities of 1 h postprandial group were full of undigested food. The evolutionary changes of character, colour and content were observed in the gastric and small intestinal contents of other postprandial groups. The movement distance of intestinal contents increased while the empty part decreased gradually. The differences among the postprandial groups were statistically significant （P<0.05）. CONCLUSIONS: After a 24 h fasting with free drinking and the following 1 h feeding, an ideal animal model can be established successfully on female SD rats, which can provide an experimental basis for postmortem interval estimation based on the changes of small intestinal contents in forensic practice.

Parasite load and seasonal migration in red deer.

Northern deer populations are typically partially migratory, but the relationship between migratory movements and parasites has received little attention. Migration often involves movement from a low-elevation winter range towards a summer range at higher elevation. In Europe these movements may also involve a gradient in abundance of Ixodes ricinus ticks, but whether tick loads on deer differ depending on migration tactic has not been quantified. Based on the examination of ears from 49 red deer (Cervus elaphus) marked with global positioning system collars, we provide the first evidence that the tick loads of deer covering longer distances between their winter and summer range, resulting in higher difference in elevation, are lower. Our study highlights that only the resident part of the red deer population will be available as year-round hosts to ticks, while a large part of the red deer population is unavailable to ticks for most of the tick questing season due to seasonal migration to higher elevation. Predicted changes in the migratory behaviour of ungulates could hence affect the proportion of the host population available to ticks in the future.

How far to go? Determinants of migration distance in land mammals.

Animal migration is a global phenomenon, but few studies have examined the substantial within- and between-species variation in migration distances. We built a global database of 94 land migrations of large mammalian herbivore populations ranging from 10 to 1638 km. We examined how resource availability, spatial scale of resource variability and body size affect migration distance among populations. Resource availability measured as normalised difference vegetation index had a strong negative effect, predicting a tenfold difference in migration distances between low- and high-resource areas and explaining 23% of the variation in migration distances. We found a weak, positive effect of the spatial scale of resource variability but no effect of body size. Resource-poor environments are known to increase the size of mammalian home ranges and territories. Here, we demonstrate that for migratory populations as well, animals living in resource-poor environments travel farther to fulfil their resource needs.

Migration timing and its determinants for nocturnal migratory birds during autumn migration.

1. Migration is a common strategy used by birds that breed in seasonal environments, and multiple environmental and biological factors determine the timing of migration. How these factors operate in combination during autumn migration, which is considered to be under weaker time constraints relative to spring migration, is not clear. 2. Here, we examine the patterns and determinants of migration timing for nocturnal migrants during autumn migration in the north-eastern USA using nocturnal reflectivity data from 12 weather surveillance radar stations and modelled diurnal probability of occurrence for 142 species of nocturnal migrants. We first model the capacity of seasonal atmospheric conditions (wind and precipitation) and ecological productivity (vegetation greenness) to predict autumn migration intensity. We then test predictions, formulated under optimal migration theory, on how migration timing should be related to assemblage-level estimates of body size and total migration distance within the context of dietary guild (insectivore and omnivore) and level of dietary plasticity during autumn migration. 3. Our results indicate seasonal declines in ecological productivity delineate the beginning and end of peak migration, whose intensity is best predicted by the velocity of winds at migration altitudes. Insectivorous migrants departed earlier in the season and, consistent with our predictions, large-bodied and long-distance insectivorous migrants departed the earliest. Contrary to our predictions, large-bodied and some long-distance omnivorous migrants departed later in the season, patterns that were replicated in part by insectivorous migrants that displayed dietary plasticity during autumn migration. 4. Our findings indicate migration timing in the region is dictated by optimality strategies, modified based on the breadth and flexibility of migrant's foraging diets, with declining ecological productivity defining possible resource thresholds during which migration occurs when winds at migration altitudes are mild. These observations provide the basis to assess how avian migration strategies may be affected by adjustments in seasonal patterns of atmospheric circulation and ecological productivity that may occur under global climate change.

Brain regions associated with visual cues are important for bird migration.

Long-distance migratory birds have relatively smaller brains than short-distance migrants or residents. Here, we test whether reduction in brain size with migration distance can be generalized across the different brain regions suggested to play key roles in orientation during migration. Based on 152 bird species, belonging to 61 avian families from six continents, we show that the sizes of both the telencephalon and the whole brain decrease, and the relative size of the optic lobe increases, while cerebellum size does not change with increasing migration distance. Body mass, whole brain size, optic lobe size and wing aspect ratio together account for a remarkable 46% of interspecific variation in average migration distance across bird species. These results indicate that visual acuity might be a primary neural adaptation to the ecological challenge of migration.

New peak broadening parameter for the characterization of separation capability in capillary electrophoresis.

The influence of separation conditions on peak broadening is usually estimated by the number of theoretical plates. Using the data available in literature and experimental data, it is shown that in pressure-assisted capillary electrophoresis the plate number is not directly related to the separation capability of conditions used. The experiments at different electrolyte flow velocities demonstrate that a higher plate number (the best separation efficiency) can be obtained with a lower peak resolution. Since ions are separated by electrophoresis due to the difference in electrophoretic mobilities, the peak width in terms of electrophoretic mobility is suggested as a new peak broadening parameter describing the separation capability of the conditions used. The parameter can be calculated using the tailing factor and the temporal peak width at 5% of the peak height. A simple equation for the resolution calculation is derived using the parameter. The advantage of the peak width in terms of mobility over other parameters is shown. The new parameter is recommended to be used not only in pressure-assisted capillary electrophoresis but also in general capillary electrophoresis when in a number of runs the virtual separative migration distance and separation capability of the conditions used change widely.

Childhood migration experience and adult health: evidence from China's rural migrants.

BACKGROUND: Place of residence plays an influential role in shaping individual development, and studies have established links between Childhood migration experience (CME) and health outcomes through maturity. Over the past three decades, China has undergone one of the largest rural-to-urban migrations, however, little is known about the effect of CME on rural migrants' adult health in China. METHODS: Data from 7035 members of the 2016 and 2018 China Labor-force Dynamics Survey were analyzed. CME was measured by whether the place of residence and place of birth changed at the age of 14 years. Three measures of health (self-assessed health, BMI, and mental health scale) were obtained. Causal inferential analysis was performed, using the Probit model, the OLS model and the Propensity Score Matching (PSM) method, to explore the impact of CME on the adult health of rural migrants. RESULTS: Overall, compared to individuals who did not migrate in childhood, the probability of reporting "very unhealthy", "rather unhealthy", and "fair" in the self-assessed health of the rural migrants with CME decreased by 0.23%, 1.55%, and 5.53%, the probability of reporting "healthy" and "very healthy" increased by 1.94% and 5.38%, the probability of BMI within the normal range was higher by 7.32%, and the mental health test scores were 0.2591 points higher significantly. Furthermore, in comparison with childhood non-migration, both cross-county and cross-city migration promoted the health status of rural migrants, but the positive effect of cross-province migration was not significant; from the gender perspective, CME could more dramatically improve rural women's adult health than men, especially in mental health. CONCLUSION: CME can significantly improve adult health, including physical and mental health, and the positive effect is more obvious among women, helping to reduce gender differences in health. For the migration distance, attention can be focused on the long-distance migrating individuals, who should get more support.

Migration costs drive convergence of threshold traits for migratory tactics.

Partial migration of some, but not all, members of a population is a common form of migration. We evaluated how migration costs influence which members migrate in 10 populations of two salmonid species. The migratory patterns of both species were evaluated based on the size at maturity for resident males, which is the threshold trait that determines the migratory tactics used within a population. In both species, this size was smaller in males located further from the sea, where migration costs are presumably higher. Moreover, the threshold sizes at maturity in males were correlated between both species. Our results suggest that migration costs are a significant convergent selective force on migratory tactics and life-history traits in nature.

Migration Behavior of Anguilla celebesensis Silver Eels within their Tomini Bay Spawning Area.

The tropical Celebes eel, Anguilla celebesensis, has a short migration between its spawning and growth habitats. Its spawning areas were hypothesized to be in Tomini Bay and the Celebes Sea after collecting their small leptocephali. However, there is no information about the silver eel oceanic spawning migration behavior of A. celebesensis. To better understand their short-distance spawning migration behavior, four large female silver eels (Eel 1-4) were equipped with pop-up satellite archival tags (PSATs) and released near the mouth of the Poso River in Tomini Bay of Sulawesi Island on 22 February (Eel 1-3) and 11 March 2010 (Eel 4). All PSATs ascended in Tomini Bay and transmitted their data. Eel 3 and 4 provided clear records of consistent diel vertical migration (DVM: eight days-Eel 3, 13 days-Eel 4) with daytime dives to mean depths of 444.7 m (Eel 3) and 539.0 m (Eel 4), where mean temperatures were 9.1°C (Eel 3) and 7.7°C (Eel 4), and nighttime ascents to mean depths of 132.8 m (Eel 3) and 112.4 m (Eel 4), where mean temperatures were 20.6°C (Eel 3) and 23.4°C (Eel 4). Eel 3 and 4 started to dive to deeper water around nautical dawn and swam up to shallower water around sunset. During nighttime, both eels swam in deeper and colder water during nights with moonlight than during nights without moonlight, and there was a negative linear relationship between experienced water temperatures with the moon in the sky and the lunar age for the eels. The A. celebesensis daily rhythm of DVM behaviors was similar to spawning-migration DVM behaviors of other anguillid species. Essential life history characteristics of A. celebesensis appear to be a short migration between freshwater growth habitat and ocean spawning habitat, and high GSI values with advanced gonadal development in downstream-migrating silver eels.

Does Migration Distance Affect Happiness? Evidence From Internal Migrants in China.

Background: Happiness is a complex concept involving many subjects such as society, psychology, and ethics. How will migration distance affect migrants' happiness under the new trend of migration in China? The goal of this paper is to analyze the influence and transmission mechanism of migration distance on happiness of migrant individuals, and the heterogeneity of this effect on urban and rural migrants. Methods: Employing data of 129,803 observations from the 2012 China Migrants Dynamic Survey, we first estimate the effects of migration distance on happiness by the ordinal logistic regression and propensity score matching (PSM) method. Second, we examine the heterogeneity of effect by splitting the sample into the urban and rural migrants. Finally, we analyze the transmission mechanism of migration distance on happiness by mediating effect model. Results: The migration distance of internal migrants in China has a significant negative impact on happiness. Urban migrant individuals show a stronger response to migration distance compared to rural counterparts. Social integration is proved as the potential mechanism through which the effect of migration distance on happiness. Conclusion: The results emphasize happiness of internal migrant and other mental health problems. Moreover, particular attention should be paid to social integration on happiness, such as strengthening the cultural exchange in different areas, narrowing the income gap between urban and rural areas, promoting rational migrant decision of individual, and enhancing the happiness of them.

Seasonal climatic niche and migration movements of Double-crested Cormorants.

Avian migrants are challenged by seasonal adverse climatic conditions and energetic costs of long-distance flying. Migratory birds may track or switch seasonal climatic niche between the breeding and non-breeding grounds. Satellite tracking enables avian ecologists to investigate seasonal climatic niche and circannual movement patterns of migratory birds. The Double-crested Cormorant (Nannopterum auritum, hereafter cormorant) wintering in the Gulf of Mexico (GOM) migrates to the Northern Great Plains and Great Lakes and is of economic importance because of its impacts on aquaculture. We tested the climatic niche switching hypothesis that cormorants would switch climatic niche between summer and winter because of substantial differences in climate between the non-breeding grounds in the subtropical region and breeding grounds in the northern temperate region. The ordination analysis of climatic niche overlap indicated that cormorants had separate seasonal climatic niche consisting of seasonal mean monthly minimum and maximum temperature, seasonal mean monthly precipitation, and seasonal mean wind speed. Despite non-overlapping summer and winter climatic niches, cormorants appeared to be subjected to similar wind speed between winter and summer habitats and were consistent with similar hourly flying speed between winter and summer. Therefore, substantial differences in temperature and precipitation may lead to the climatic niche switching of fish-eating cormorants, a dietary specialist, between the breeding and non-breeding grounds.

Who Moves to Whom? Gender Differences in the Distance Moved to a Shared Residence.

Although the migration of couples and families is well examined, the migration that occurs at the start of co-residence has only been minimally studied. This study examines (1) whether women move more often and move over longer distances at the start of co-residence and (2) whether gender differences (if any) stem from compositional differences between women and men, such as gender differences in ties, or if they are the consequence of the within-couple distribution of bargaining power. The analyses are performed on Swedish population register data from 1991 to 2008, including longitudinal information on the residence of all couples who either married or had a child as cohabitants in 2008, backtracking them to the year of union formation. The results indicate that women are more prone to move for the sake of their male partner in the process of union formation than vice versa. If partners lived in close proximity prior to co-residence, the woman's increased likelihood of moving and longer distance moved is nearly completely explained by power imbalances in the couple. Gender differences in ties only have minor importance in explaining gender differences in these types of migration patterns. If partners lived far apart prior to co-residence, gender differences are particularly pronounced. These differences remain after adjusting for the two partners' relative resources. We contribute to the family migration literature by suggesting that women's higher propensity to move and their longer distance moved are indications that even couples' decisions at the start of co-residence are made in favour of the man's career.

The start of migration correlates with arrival timing, and the total speed of migration increases with migration distance in migratory songbirds: a cross-continental analysis.

BACKGROUND: Anthropogenic changes in the climate and environment have globally affected ecological processes such that the spatiotemporal occurrence of the main annual cycle events (i.e., breeding, wintering, moulting, and migration) has shifted in migratory birds. Variation in arrival timing at migratory destinations can be proximately caused by an altered start of migration, total migration distance, and/or total speed of migration. Quantifying the relative contributions of these causes is important because this will indicate the mechanisms whereby birds could potentially adjust their annual cycle in response to global change. However, we have relatively little quantitative information about how each of these factors contributes to variation in arrival timing. My main aims are to estimate how arrival timing is correlated with variation in the start of migration and the total migration distance and how the total speed of migration may change with the total migration distance and body mass in a comprehensive analysis including multiple species. METHODS: For this purpose, I considered individual tracks covering complete migrations from multiple species and distinguished between within- and between-species effects. RESULTS: Assuming that the within- and between-species effects quantified under this approach agree with the effects acting at the individual level, starting migration one day later or increasing the total migration distance by 1000 km would result in later arrival timing by 0.4-0.8 days or 2-5 days, respectively. The generality with which the start of migration is correlated with arrival timing within species suggests that this is the general biological mechanism regulating arrival timing, rather than the total migration distance. The total speed of migration was positively correlated with the total migration distance but not with the bird's body mass. CONCLUSIONS: As the start of migration is endogenously controlled and/or affected by hatching date, directional selection can probably act on existing within-species/within-population variation to alter arrival timing. This factor and the importance of variation in the start of migration for arrival timing suggest that migratory species/populations in which there is sufficient variation in the start of migration and transgenerational processes affect the corresponding timing may present an advantage over others in coping with anthropogenic-induced global changes.

Body size, developmental instability, and climate change.

Development is often temperature-dependent. We hypothesized smaller size and larger asymmetry with increasing temperatures. However, we also predicted associations with asymmetry to differ among traits that differ in their degree of functional importance (especially the functional wings in migratory birds were predicted to be more canalized), timing of development (skeletal [femur, tarsus, and humerus] vs. feather [wing and tail traits]). We analyzed a large dataset of which we included species with at least 20 specimens resulting in 5533 asymmetry values in 1593 individuals from 66 species. There was a consistent significant decrease in size with temperature across all traits. Fluctuating asymmetry (FA) for wings and femur was on average lower, suggesting higher canalization, and it decreased with migration distance, however that was not the case for the other traits. FA increased with increasing temperature for wings, but not for the other characters, where the different responses of different characters to temperature were significant. Because there was no significant three-way interaction between temperature, migration distance, and character, the asymmetry-temperature response was similar in migratory and resident species. These findings imply that climate warming reduces size of all traits and decreases developmental instability of wings in birds.

Modelling and assessment of accidental oil release from damaged subsea pipelines.

This paper develops a 3D, transient, mathematical model to estimate the oil release rate and simulate the oil dispersion behavior. The Euler-Euler method is used to estimate the subsea oil release rate, while the Eulerian-Lagrangian method is employed to track the migration trajectory of oil droplets. This model accounts for the quantitative effect of backpressure and hole size on oil release rate, and the influence of oil release rate, oil density, current speed, water depth and leakage position on oil migration is also investigated in this paper. Eventually, the results, e.g. transient release rate of oil, the rise time of oil and dispersion distance are determined by above-mentioned model, and the oil release and dispersion behavior under different scenarios is revealed. Essentially, the assessment results could provide a useful guidance for detection of leakage positon and placement of oil containment boom.