Seasonal variation of vessel pits in sapwood: microscopical analyses of the morphology and chemical components of pit membrane encrustations in Fraxinus mandshurica.

BACKGROUND AND AIMS: Pit pairs and their filter-like partition, i.e. pit membranes, play important roles as water pathways, barriers and regulators in the water-conducting system of angiosperms. In Fraxinus species, the intervessel and vessel-parenchyma pit membranes in sapwood are normally encrusted during winter. Although these encrustations inevitably influence the performance of pits, their properties and functions remain unclear. This study aimed to reveal the morphological and chemical characteristics of encrustations in F. mandshurica in order to deepen understanding of the seasonal encrustation of pit membranes. METHODS: Seasonal and positional variations in the presence and morphology of encrustations were examined by field-emission scanning electron microscopy (FE-SEM). Cryo-FE-SEM for freeze-fixed greenwood samples was conducted to clarify whether encrustations were present in living trees. Chemical components were examined by histochemical staining using light and electron microscopies, immunofluorescence labelling and ultraviolet microspectroscopy. KEY RESULTS: Encrustations began to deposit in fall before leaf senescence and disappeared in spring before bud flushing. They infiltrated within the pit membranes, which suggested that they severely limit the permeation of pits. The encrustations differed in morphology among positions: they entirely filled the pit chambers in latewood, while they covered the pit membranes in earlywood. The encrustations were similarly observed in the samples that were freeze-fixed immediately after collection, indicating that they are present in living trees. The encrustations contained polysaccharides, including xyloglucan and homogalacturonan, and phenolic compounds, possibly including flavonoids and coumarins. These chemical components were also detected in droplets found in the latewood vessels with the encrustations, suggesting that the materials constituting encrustations were supplied through the vessel lumens. CONCLUSIONS: Encrustations undoubtedly cover the pit membranes in living F. mandshurica trees in winter and their morphology and chemical composition indicate that they are impermeable, have positional differences in function and are characterised by elaborate deposition/removal processes.

Seasonal and diurnal variations in soil respiration rates at a treeline ecotone and a lower distribution limit of subalpine forests.

This study examined the seasonal and diurnal variations in soil respiration rates (RS) during a growing season at the treeline ecotone (2,800 m) and the lower distribution limit (1,600 m) of subalpine forests on a volcanic mountain in Japan. The aboveground biomass, the total RS during the growing season, and the RS per day during the growing season were lower at 2,800 m than those at 1,600 m. Seasonal RS variations positively correlated with those of soil and air temperatures at both elevations, and this tendency was more apparent at 1,600 m than 2,800 m. The mean volumetric soil water content (WS) during the growing season was much lower at 2,800 m than 1,600 m because of the scoria substrate at 2,800 m. The monthly mean diel cycle of RS was positively correlated with the soil temperature at each elevation every month, whereas that at 1,600 m was negatively correlated with that of the WS. The RS at 2,800 m decreased during the daytime especially in August, despite no changes in the WS. The decrease in RS after precipitation at 1,600 m was higher than that at 2,800 m. Seasonal and diurnal RS variations could be reproduced from soil and air temperatures, and WS. Estimating soil respiration rate from these variables will help understand the future carbon budget of forests due to global warming.

Expression of cholesterol synthesis and steroidogenic markers in females of the Chinese brown frog (Rana dybowskii) during prespawning and prehibernation.

The oviduct of the Chinese brown frog (Rana dybowskii) expands in prehibernation rather than in prespawning, which is one of the physiological phenomena that occur in the preparation for hibernation. Steroid hormones are known to regulate oviductal development. Cholesterol synthesis and steroidogenesis may play an important role in the expansion of the oviduct before hibernation. In this study, we investigated the expression patterns of the markers that are involved in the de novo steroid synthesis pathway in the oviduct of R. dybowskii during prespawning and prehibernation. According to histological analysis, the oviduct of R. dybowskii contains epithelial cells, glandular cells, and tubule lumens. During prehibernation, oviductal pipe diameter and weight were significantly larger than during prespawning. 3-Hydroxy-3-methylglutaryl CoA reductase (HMGCR), low-density lipoprotein receptor (LDLR), steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), and steroidogenic factor 1 (SF-1) were detected in epithelial cells in prehibernation and glandular cells during prespawning. HMGCR, LDLR, StAR, and P450scc protein expression levels were higher in prehibernation than during prespawning, but the SF-1 protein expression level did not significantly differ. HMGCR, LDLR, StAR, P450scc (CYP11A1), and SF-1 (NR5A1) mRNA expression levels were significantly higher in prehibernation compared with prespawning. The transcriptome results showed that the steroid synthesis pathway was highly expressed during prehibernation. Existing results indicate that the oviduct is able to synthesize steroid hormones using cholesterol, and that steroid hormones may affect the oviductal functions of R. dybowskii.

Stories of a water-table: anomalous depressions, aquitard breaches and seasonal implications, Shelby County, Tennessee, USA.

An extensive water level survey of the water-table aquifer (i.e., shallow aquifer) within Shelby County, Tennessee, was conducted in the dry (fall 2020) and wet (spring 2021) seasons. Water-table surfaces were generated using cokriging to observe seasonal differences to identify anomalous water-table depressions, indicative of an underlying aquitard breach. Seasonal differences were attributed to non-coincident control and timing between the surveys and when optimum dry (fall) and wet (spring) conditions existed, as observed through comparisons with continuous historical water levels from 12 shallow monitoring wells. Additionally, data from fall 2020 were compared to previous studies in 2005 and 2015 to determine decadal changes in levels and shape of the water-table surface which were mostly attributed to changes in data control and potential climate variations. A prediction error map was generated from the 2020 dataset to identify areas of the county with high-prediction error (>7.0 m) to offer guidance on where future well control would be optimal.

Seasonal variations of microbial community and antibiotic resistome in a suburb drinking water distribution system in a northern Chinese city.

Antibiotic resistance genes (ARGs) are an emerging issue for drinking water safety. However, the seasonal variation of ARGs in drinking water distribution systems (DWDS) is still unclear. This work revealed the tempo-spatial changes of microbial community, ARGs, mobile genetic elements (MGEs) co-occurring with ARGs, ARG hosts in DWDS bulk water by means of metagenome assembly. The microbial community and antibiotic resistome varied with sampling season and site. Temperature, ammonia, chlorite and total plate count (TPC) drove the variations of microbial community structure. Moreover, environmental parameters (total organic carbon (TOC), chlorite, TPC and hardness) shifted antibiotic resistome. ARGs and MGEs co-occurring with ARGs showed higher relative abundance in summer and autumn, which might be attributed to detached pipe biofilm. In particular, ARG-bacitracin and plasmid were the predominant ARG and MGE, respectively. ARG hosts changed with season and site and were more diverse in summer and autumn. In winter and spring, Limnohabitans and Mycobacterium were the major ARG hosts as well as the dominant genera in microbial community. In addition, in summer and autumn, high relative abundance of Achromobacter and Stenotrophomonas were the hosts harboring many kinds of ARGs and MGEs at site in a residential zone (0.4 km from the water treatment plant). Compared with MGEs, microbial community had a greater contribution to the variation of antibiotic resistome. This work gives new insights into the dynamics of ARGs in full-scale DWDS and the underlying factors.

Interpreting the COVID effect on atmospheric constituents over the Indian region during the lockdown: chemistry, meteorology, and seasonality.

Most of the published articles which document changes in atmospheric compositions during the various lockdown and unlock phases of COVID-19 pandemic have made a direct comparison to a reference point (which may be 1 year apart) for attribution of the COVID-mediated lockdown impact on atmospheric composition. In the present study, we offer a better attribution of the lockdown impacts by also considering the effect of meteorology and seasonality. We decrease the temporal distance between the impacted and reference points by considering the difference of adjacent periods first and then comparing the impacted point to the mean of several reference points in the previous years. Additionally, we conduct a multi-station analysis to get a holistic effect of the different climatic and emission regimes. In several places in eastern and coastal India, the seasonally induced changes already pointed to a decrease in PM concentrations based on the previous year data; hence, the actual decrease due to lockdown would be much less than that observed just on the basis of difference of concentrations between subsequent periods. In contrast, northern Indian stations would normally show an increase in PM concentration at the time of the year when lockdown was effected; hence, actual lockdown-induced change would be in surplus of the observed change. The impact of wind-borne transport of pollutants to the study sites dominates over the dilution effects. Box model simulations point to a VOC-sensitive composition.

The seasonal changes of the gut microbiome of the population living in traditional lifestyles are represented by characteristic species-level and functional-level SNP enrichment patterns.

BACKGROUND: Most studies investigating human gut microbiome dynamics are conducted on humans living in an urban setting. However, few studies have researched the gut microbiome of the populations living traditional lifestyles. These understudied populations are arguably better subjects in answering human-gut microbiome evolution because of their lower exposure to antibiotics and higher dependence on natural resources. Hadza hunter-gatherers in Tanzania have exhibited high biodiversity and seasonal patterns in their gut microbiome composition at the family level, where some taxa disappear in one season and reappear later. Such seasonal changes have been profiled, but the nucleotide changes remain unexplored at the genome level. Thus, it is still elusive how microbial communities change with seasonal changes at the genome level. RESULTS: In this study, we performed a strain-level single nucleotide polymorphism (SNP) analysis on 40 Hadza fecal metagenome samples spanning three seasons. With more SNP presented in the wet season, eight prevalent species have significant SNP enrichment with the increasing number of SNP calling by VarScan2, among which only three species have relatively high abundances. Eighty-three genes have the most SNP distributions between the wet season and dry season. Many of these genes are derived from Ruminococcus obeum, and mainly participated in metabolic pathways including carbon metabolism, pyruvate metabolism, and glycolysis. CONCLUSIONS: Eight prevalent species have significant SNP enrichments with the increasing number of SNP, among which only Eubacterium biforme, Eubacterium hallii and Ruminococcus obeum have relatively high species abundances. Many genes in the microbiomes also presented characteristic SNP distributions between the wet season and the dry season. This implies that the seasonal changes might indirectly impact the mutation patterns for specific species and functions for the gut microbiome of the population that lives in traditional lifestyles through changing the diet in wet and dry seasons, indicating the role of these variants in these species' adaptation to the changing environment and diets.

Freezing resistance and behavior of winter buds and canes of wine grapes cultivated in northern Japan.

In high-latitude regions, the cold hardiness of buds and canes of grapevine is important for budburst time and yield in the next season. The freezing resistance of buds and canes sampled from six wine grapes currently cultivated in Hokkaido, Japan, all of them grown from autumn to winter, was investigated. A significant difference between the cultivars in their freezing resistance was detected in the buds harvested in winter. In addition, outstanding differences in the lower temperature exotherms (LTE) related to the supercooling ability of tissue cells happened in the winter buds, and there is a close relationship between freezing resistance and LTE detected in the winter buds. This suggests that the supercooling ability of tissue cells in winter buds is strongly related to the freezing resistance. However, detailed electron microscopy exposed that the differences in freezing resistance among cultivars appeared in freezing behavior of leaf primordium rather than apical meristem. This indicated that as the water mobility from the bud apical meristem to the spaces around the cane phloem progressed, the slightly dehydrated cells improved the supercooling ability and increased the freezing resistance.

[Seasonal changes in blood pressure and related factors among older patients receiving home medical care].

AIM: We investigated seasonal variations in blood pressure (BP) and factors related to these variations among older patients receiving home medical care. METHOD: A total 57 patients ≥ 65 years old receiving home medical care who participated in the Osaka Home Care REgistry study (OHCARE), a prospective cohort study, were included. We investigated the seasonal patient characteristics and variations in the BP. In addition, to determine the influence of seasonal variations in the systolic blood pressure (SBP) on the occurrence of clinical events (hospitalization, falls and death), we classified patients into larger- and smaller- change groups based on the median seasonal variations in SBP. RESULT: About 60% of subjects were very frail or bedridden. The mean BP was higher in winter than in summer (124.7±11/69.5±7 vs.120.5±12/66.9±8 mmHg) (P< 0.01). On comparing the characteristics of the two groups with larger and smaller changes in the SBP, the group with large BP changes had a significantly lower BP in summer than the group with small BP changes. In addition, the incidence of "hospitalization" was significantly higher in the group with large BP changes than in the group with small BP changes (P = 0.03). CONCLUSION: The present study revealed that there were seasonal changes in the BP in older patients receiving home medical care. It was also suggested that seasonal changes in the BP might be associated with the risk of hospitalization events. Given these BP variations, doctors and visiting nurses should be alert for systemic abnormalities, especially in frail patients receinving home medical care.

The effects of season change and fasting on Brown adipose tissue FDG-PET in mice.

It is widely reported that BAT is more frequently observed in patients during the winter season, and its activities could vary significantly under different conditions. However, whether this phenomenon is entirely caused by low temperature or other factors is not very clear. In this study, we tried to explore the seasonal fluctuation of FDG-PET BAT using mouse models that were from the same genetic breed and raised in a well-controlled environment. We also compared these variations with the effects of fasting and cold stimulation on BAT activities in these mice. In overnight fasted mice, the FDG-PET BAT was the highest in standardized uptake value (SUV) in the winter season. The values were much lower in all other seasons, especially in the summer. Compared to regular feeding, overnight fasting reduced BAT SUV, and refeeding after fasting could fully recover BAT activities. Fasted mice also did not respond to cold environment stimulation. After refeeding, their BAT thermogenic activities became normal. These results suggest that BAT FDG-PET SUV measurements vary significantly with the season and highlight the importance of taking into account the seasonal effect and fasting status in BAT evaluation studies using FDG-PET imaging.

Elevation rather than season determines the assembly and co-occurrence patterns of soil bacterial communities in forest ecosystems of Mount Gongga.

Seasonal dynamics of soil microbial communities may influence ecosystem functions and services. However, few observations have been conducted on the dynamics of a bacterial community assembly across seasons in different elevations in mountain forest ecosystems. In this study, the diversity, compositions, community assembly processes, and co-occurrence interactions of soil bacterial communities were investigated using Illumina sequencing of 16S rRNA genes across different seasons during two consecutive years (2016 and 2017) at two elevational sites in Mount Gongga, China. These two sites included an evergreen broad-leaved forest (EBF, 2100 m a.s.l.) and a dark coniferous forest (DCF, 3000 m a.s.l.). The results showed that bacterial diversity and structure varied considerably between the two elevational sites with only limited seasonal variations. Interannuality had a significant effect on the diversity and structure of soil bacterial communities. The bacterial alpha diversity was significantly higher at site EBF(e.g., OTUs richness, 2207 ± 276) than at site DCF(e.g., OTUs richness, 1826 ± 315). Soil pH, temperature, elevation, and water content were identified as important factors shaping soil bacterial communities in the mountain forests. Bacterial community assembly was primarily governed by deterministic processes regardless of elevation and season. Deterministic processes were stronger at site DCF than at EBF. The soil bacterial community at site EBF harbored a more complex and connected network with less resistance to environmental changes. Overall, this study showed that seasonal dynamics of bacterial communities were much weaker than those along elevations, implying that a single-season survey on a bacterial community along an elevational gradient can represent overall changes in the bacterial community. KEY POINTS: • Seasonal dynamics of soil bacterial communities were studied in Mount Gongga. • The bacterial community was mainly affected by elevation rather than season. • Deterministic processes dominated bacterial community assembly. • The bacterial network was more complex but less stable at EBF than at DCF.

Seasonal changes in indoor airborne fungal concentration in a hematology ward.

Invasive fungal disease (IFD) is an important infectious complication of hematological disorders, especially in hematopoietic stem cell transplantation recipients. Evidences suggest seasonal and/or geographical variations in the airborne fungal counts and a relationship between those counts and the incidence of IFD. We evaluated the concentrations of indoor airborne fungi quantitated over the course of one year in a hematology ward in Japan. In January, April, July, and October, fixed volumes of air samples were obtained by an air sampler in a hematology ward not equipped with a high-efficiency particulate air filter and incubated in fugal cultures. Samples were also obtained from a protective environment in the same ward and were evaluated. The number of fungal colonies per 50 L of sampled air was highest in October (median 2.25 (range, 0.2-7.0)), which was significantly higher than those in the other three months (0.1 (range, 0-1.0) in January; 0 (0-0) in April; 0.55 (0-2.5) in July; P < 0.01)). Commonly identified pathogens included Penicillium and Cladosrporium species, but Aspergillus species was detected only in July and October samples. These results suggest a seasonal variation in indoor airborne fungal concentrations in Japan, which could affect the epidemiology of IFD.

Isotope analysis reveals proportional change and site-selection variation of river- and lake-produced eggs of a landlocked migratory fish.

Changes in the proportions of river- and lake-produced eggs of a landlocked amphidromous fish, ayu (Plecoglossus altivelis altivelis) in the Lake Biwa water system, Japan, were monitored by stable isotope analysis, based on different δ15 N and δ13 C values of prey organisms between the lake and its tributaries. During the 3 month reproduction season, the δ15 N values of spawned eggs decreased with time. This result implies that there was a shift from lake-produced eggs to river-produced eggs within a reproductive season, based on the observation that adult fish in the lake had previously been shown to have eggs with distinctly higher δ15 N values in their ovaries than those in the tributaries. This explanation was also supported by the change in δ13 C values of the spawned eggs. Furthermore, eggs with lower δ15 N and higher δ13 C values tended to be spawned at less variable depths, suggesting that females spawning river-produced eggs selected the spawning sites from a narrower range. We conclude that stable isotope ratios of spawned eggs can be indicators of the relative contributions of different food chains and can enable comparisons of reproductive characteristics between types of egg.

Effects of mountain urbanization on greenhouse gas emissions from municipal solid waste management practices in Southwest China.

Urbanization is occurring globally at an unprecedented rate. The byproduct of this mounting urbanization is an increase in municipal solid waste (MSW), which has a significant effect on population health and the surrounding environment. This trend poses a challenge to the cities responsible for managing waste in a socially and environmentally acceptable manner. Effective waste management strategies depend on local waste characteristics, which vary under different cultural, climatic, and socioeconomic conditions. It is important to note that MSW disposal represents one of the largest sources for anthropogenic greenhouse gas (GHG) emissions. This study found a direct proportional urban and rural gradient between household income and GHG emissions under a typical urban household size. The distribution of GHG is U-shaped. This study found that urbanization exhibited a pattern of continuous growth, and the effect of urbanization was less than the effect of the population in magnitude. The correlation between GHG and income level in recent urban sprawl along a north-south transect was lower than during the period of early urban expansion.

Behavioral and endocrine responses to season and social dynamics of captive male southern hairy-nosed wombats (Lasiorhinus latifrons).

Although southern hairy-nosed wombats (SHN wombats; Lasiorhinus latifrons) rarely breed in captivity, further knowledge of their reproductive physiology and behavior is likely to improve their breeding potential. This study examined the effect of seasonal variation and changes in social dynamics on the physiology and behavior of a captive population of male SHN wombats (n = 6). Seasonal changes in urinary testosterone metabolites (UTM), urinary cortisol metabolites (UCM), qualitative estimates of spermatorrhoea (QS), aggressive behavior and reproductive behavior were measured over an 11-month period. While there was no effect of month on QS (GLM ANOVA, P = 0.27), reproductive behavior (GLM ANOVA, P = 0.19) or aggressive behavior (Tukey pairwise comparisons), the secretion of UTM (GLM ANOVA, P = 0.051) was only marginally affected by season, compared to that reported for wild male SHN wombats. Mean UCM concentrations of July and August 2016 were significantly higher than those between October 2015 and January 2016 (Tukey pairwise comparisons). To examine social dynamics, two trials of animal positioning exchange with the enclosure system were implemented and behavioral data were examined for each trial over a six week period; UTM, UCM and general behaviors (n = 27) were measured for each trial. Neither UTM nor UCM concentration varied significantly (P ≥ 0.45) before and after the exchanges. "Scratching" decreased at the group level following the animal exchange in both trials, suggesting reduction in self-grooming may be a behavioral response to novel stimuli. UCM and UTM concentrations were both positively correlated with "standing still" and "body rub" behaviors. This may be evidence of a hormonal control of a "freezing behavioral response" to external stimuli and marking behavior, respectively. As there was no evidence that changing the social dynamics affected reproductive or agonistic behavior or hormone concentrations, it was concluded that captive male wombats in this study showed reduced reproductive seasonality compared to wild wombats and that animal exchange resulted in a behavioral response to novel stimuli but was not sufficient to affect testosterone or cortisol secretion, within the context of our study.

Heavy Metal Contamination in the Cultivated Oyster Crassostrea rivularis and Associated Health Risks from a Typical Mariculture Zone in the South China Sea.

With the rapid development of mariculture in potentially contaminated regions in China and the world, food safety, is a growing concern. To evaluate heavy metals and their associated health risks in the cultivated oyster Crassostrea rivularis, the concentrations of heavy metals (Cd, Cr, Pb, Zn) in oysters and water/sediment were examined in a typical mariculture environment (Kaozhou Bay, South China Sea). Trends in the seasonal dynamics of heavy metals in oysters revealed a potential synergistic effects among the concentrations of Cd, Cr, and Zn; trends associated with Pb were less clear, although the ability of oysters to bioaccumulate and depurate Pb was excellent. Bioconcentration factors (BCF) indicated that C. rivularis has a strong ability to accumulate heavy metals, and the BCF was the highest for Zn (2.32 × 105), followed by Cd (6.84 × 104), Pb (2.77 × 104) and Cr (1.23 × 103) through the four seasons. Results showed that Cd concentrations in oysters could pose a risk to human health (HQ > 1). This study, therefore, suggests that there are potential human health risks due to heavy metal exposure through the consumption of C. rivularis from mariculture zones in South China Sea.

Seasonal expressions of follicle-stimulating hormone receptor and luteinizing hormone receptor in the scented gland of the male muskrat (Ondatra zibethicus).

Accumulating evidence has shown that follicle-stimulating hormone (FSH) and luteinizing hormone (LH) may influence the functions of nongonadal tissues in addition to their classic target gonads. Our previous studies revealed that the scented glands of male muskrats expressed prolactin receptor, steroidogenic enzymes, and inhibin/activin subunits. To further seek the evidence of the activities of pituitary gonadotropins in scented glands, we investigated the seasonal expression patterns of FSH receptor (FSHR) and LH/choriogonadotropin receptor (LHCGR). The weight and size of scented glands during the breeding season were significantly higher than those during the nonbreeding season. Immunohistochemical studies showed that FSHR was present in the serous cells of scented glands, whereas LHCGR was present in the interstitial cells. The protein and mRNA expression levels of FSHR and LHCGR were significantly higher in the scented glands during the breeding season than those during the nonbreeding season. Importantly, the levels of circulating FSH and LH were remarkably higher during the breeding season. Taken together, these results suggested that gonadotropins may affect the function of muskrat scented gland via the locally expressed receptors in a season-dependent manner.

Attribution of seasonal leaf area index trends in the northern latitudes with "optimally" integrated ecosystem models.

Significant increases in remotely sensed vegetation indices in the northern latitudes since the 1980s have been detected and attributed at annual and growing season scales. However, we presently lack a systematic understanding of how vegetation responds to asymmetric seasonal environmental changes. In this study, we first investigated trends in the seasonal mean leaf area index (LAI) at northern latitudes (north of 30°N) between 1982 and 2009 using three remotely sensed long-term LAI data sets. The most significant LAI increases occurred in summer (0.009 m2  m-2  year-1 , p < .01), followed by autumn (0.005 m2  m-2  year-1 , p < .01) and spring (0.003 m2 m-2  year-1 , p < .01). We then quantified the contribution of elevating atmospheric CO2 concentration (eCO2 ), climate change, nitrogen deposition, and land cover change to seasonal LAI increases based on factorial simulations from 10 state-of-the-art ecosystem models. Unlike previous studies that used multimodel ensemble mean (MME), we used the Bayesian model averaging (BMA) to optimize the integration of model ensemble. The optimally integrated ensemble LAI changes are significantly closer to the observed seasonal LAI changes than the traditional MME results. The BMA factorial simulations suggest that eCO2 provides the greatest contribution to increasing LAI trends in all seasons (0.003-0.007 m2  m-2  year-1 ), and is the main factor driving asymmetric seasonal LAI trends. Climate change controls the spatial pattern of seasonal LAI trends and dominates the increase in seasonal LAI in the northern high latitudes. The effects of nitrogen deposition and land use change are relatively small in all seasons (around 0.0002 m2  m-2  year-1 and 0.0001-0.001 m2  m-2  year-1 , respectively). Our analysis of the seasonal LAI responses to the interactions between seasonal changes in environmental factors offers a new perspective on the response of global vegetation to environmental changes.

Seasonal fluctuations in body weight during growth of Thoroughbred racehorses during their athletic career.

BACKGROUND: Domesticated horses adapt to environmental conditions through seasonal fluctuations in their metabolic rate. The seasonal change of metabolic rates of domesticated horses in pastures is documented. However, there are few investigations on seasonal body weight change of domesticated horses housed in stables, which are provided constant energy intake throughout the year. Both seasonal changes and gain in body weight of racehorses during their athletic career is known to a lesser extent because their body weight are not measured in most countries. Here, we used a seasonal-trend decomposition method to conduct a time series analysis of body weight of Thoroughbred racehorses participating in flat races held by the Japan Racing Association from 1 January 2002 to 31 December 2014. RESULTS: We acquired 640,431 body weight measurements for race starts and included 632,540 of these in the time series analysis. Based on seasonal component analysis, the body weight of male and gelding horses peaked in autumn and winter and reached its nadir in summer. In contrast, the body weight of female horses peaked in autumn and reached the nadir in spring. Based on trend component analysis, most of the increase in body weight was observed when all sexes approached 5 years of age. The slope of the body weight gain was smaller after that, and an approximately 30 kg gain was observed during their careers. CONCLUSION: These results indicate that the body weight of a Thoroughbred racehorse fluctuates seasonally, and that there may be sex differences in energy balance mechanisms. Moreover, the present results suggest that the physiological development of Thoroughbred racehorses is completed just before they reach 5 years of age.

Intra-individual changes in haemosporidian infections over the nesting period in great tit females.

Prevalence of haemosporidian parasites in bird populations varies temporally both between years and within a year. In contrast to variation at the population level, relatively little is known about variation in infection attributes at the individual level, especially in non-migratory species. We examined intra-individual changes in the presence and identity of haemosporidian parasites (genera Plasmodium and Haemoproteus) over the course of the nesting period in females of great tits (Parus major)-a species considered to be resident over much of its distribution range. Birds were sampled during two stages of the nesting period: nest building and nestling rearing. The mean time interval between sampling occasions was 43 days. Between the first and second samplings, 30.6% of females gained at least one parasite lineage and 18.5% lost the lineage. Haemoproteus gains were over three times more common than Plasmodium gains. The probability of the lineage gain decreased with the date of the first sampling, was higher in individuals in better body condition and differed between years, but was not associated with the host age. The probability of the lineage loss was not explained by any of the considered parameters except for year. These results indicate that in a large proportion of a population, infection attributes (presence/absence and/or parasite identity) may change over the nesting period and the occurrence of such changes may be associated with the individual quality. Consequently, this phenomenon should be taken into account to correctly interpret parasite-mediated effects.