The annual cycle of shedding Eimeria oocysts by European bison (Bison bonasus) in the Bialowieza Primeval Forest, Poland

Between April 2008 and March 2009, we analyzed the pattern of coccidian oocysts present in the feces of the European bison (Bison bonasus L., 1758) and found 4 species (Eimeria bovis , E. canadensis, E. ellipsoidalis, E. zuernii) previously reported from this host and 3 species (Eimeria alabamensis, E. cylindrica, E. pellita) that are new host and locality records. All the species occurred in bison females, and only 4 occurred in males; E. bovis was the most prevalent in both sexes. The overall prevalence of Eimeria spp. invasion reached 34.7% in cows and 13.9% in bulls. The highest prevalence was noted in early spring, with a peak in April, and the lowest in late autumn and winter. The oocyst count per gram of feces (OPG) varied from 50 to 1,350; no symptoms of clinical coccidiosis were observed. We found a significant influence of winter aggregations of bison on shedding of coccidian oocysts. The prevalence and OPG values were higher in bison congregating in large numbers around winter-feeding sites in comparison to other sites. We suggest that the coming together of cows during the growing season impacts the gender-related differences in prevalence and the number of coccidian species involved. This observation probably results from an increased production of oocysts by sub-clinically infected individuals in high-density bison populations.     

Daily patterns of body mass gain in four species of small wintering birds

Theoretically, the trajectories describing the daily accumulation of body reserves are expected to differ between bird species in relation to whether or not they hoard food. To carry reserves on the body may be costly and hoarding species can be expected to hoard food early in the day when light and retrieve it in the afternoon, with a concomitant rapid increase in body mass. Also, the increased food predictability resulting from being able to consume hoarded food late in the day should lead to a relatively faster gain in body reserves in the afternoon in hoarding species compared to non-hoarders. Non-hoarders may have to hedge against possible afternoon losses of foraging opportunities by accumulating more reserves early in the day.
In this study the daily patterns of body mass gain in four small bird species resident during winter in Scandinavia are described. Individually known birds were trained to come to a permanent feeder and their body masses were recorded every hour throughout the day with a remote-controlled balance. The hoarding willow tit Parus montanus , marsh tit P. palustris and European nuthatch Sitta europaea all displayed the most rapid gain in body mass in the early hours of the day. After the initial burst in the morning, reserves were accumulated at a roughly constant rate for the remainder of the day. In contrast, the non-hoarding great tit P. major apparently gained body reserves at a more even rate. The daily pattern of body mass gain found in the hoarding species differs from prevailing theoretical predictions, whereas the pattern in the non-hoarding great tit is in a better agreement with theory, from which this pattern has been predicted repeatedly.     

Simulation of day-length encoding in the SCN: from single-cell to tissue-level organization

The circadian pacemaker of the SCN is a heterogeneous structure containing many single-cell oscillators that display phase differences in gene expression and electrical activity rhythms. Thus far, it is unknown how single neurons contribute to the population signal measured from the SCN. The authors used single-unit electrical activity rhythms that have previously been recorded in SCN slices and investigated in simulation studies how changes in pattern shape and distribution of single neurons alter the ensemble activity rhythm of the SCN. The results were compared with recorded ensemble rhythms. The simulations show that single units should be distributed in phase to render the recorded multiunit waveform and that different distributions can account for the multiunit pattern of the SCN, including a bimodal distribution. Vice versa, the authors show that the single-unit distribution cannot be inferred from the ensemble pattern. Photoperiodic encoding by the SCN relies on changes in waveform of the neuronal output from the SCN and received special attention in this study's simulations. The authors show that a broadening or narrowing of the multiunit pattern can be based on changes in phase differences between neurons, as well as on changes in the circadian pattern of individual neurons. However, these mechanisms give rise to differences in the maximal discharge level of the multiunit pattern, leading to testable predictions to distinguish between the 2 mechanisms. If single units broaden their activity pattern in long days, the maximum frequency of the multiunit activity should increase, while an increase in phase difference between the single-unit activity rhythms should lead to a decrement in maximum frequency. The simulations also show that coding for day-length by an evening and morning oscillator is not self-evident and will only work under a limited set of conditions in which the distribution within each component and temporal distance between the components is taken into account. While the simulations were based on single-cell and multiunit electrical activity patterns, they are also relevant for understanding the relation between single-cell and population molecular expression profiles.     

Behavioural Rhythms of Land Snails in the Field

Circadian and circannual behavioural rhythms of Helix are described in the field. Laboratory studies demonstrate the existence of an endogenous component for these rhythms. The effects of the environmental factors on the snail activities are multiple: light/dark and cold/warm cycles synchronise the behavioural rhythms; a masking effect is observed when it rains since the animals are active throughout the 24 h day; high temperature and low relative humidity cause a complete cessation of activities. In addition, social interactions between and within species can modulate the shape of the rhythms driven by the biological clock.     

Might cardiac catheterization influence diurnal rhythm of the steroid stress hormones secretion?

Glucocorticoids (GCs) are steroid hormones produced by the adrenal cortex in reaction to stress stimuli. GCs production is not stable over a 24-hour period; the plasma concentration peaks in the morning (approximately upon awakening) and then the plasma levels decrease, reaching the nadir in the evening. In our experiments, the levels of cortisol, cortisone, DHEA and DHEAS were tested in young female pigs (n=23) during heart catheterization at two different day times (in the morning and in the afternoon). The non-parametric Mann-Whitney test for statistical analysis was used. We found only minimal statistical differences in studied markers between the morning and afternoon group (p>0.05). The absence of circadian variation in GCs levels could originate either at an early age of our experimental pigs, or in stressful conditions on the experiment day, or most likely the day before (e.g. social isolation, fasting, transport, and catheterization), respectively. We can conclude there is no difference in the stress load between morning and afternoon experiments, and therefore we can assume the stress load is not a limiting factor for the timing when catheterization should be preferably performed.     

Group size, spatial segregation and activity of wild sympatric vicuñas Vicugna vicugna and guanacos Lama guanicöe

Group size, activity and spatial segregation of sympatric guanacos and vicuñas have been investigated in the wild in the Catamarca Andes, Argentina. A total of 65 groups of vicuñas and 32 of guanacos was sighted. The size of vicuña and guanaco groups (mean ± SD: 4.8 ± 4.5 individuals and 3.5 ± 3.6 individuals respectively) fell within the range reported by other studies. The occurrence of solitary guanacos was unusually high. Spatial overlap between vicuñas and guanacos was wide and occurred from 4000 to 4200 m altitude. Possibly, the two species attained segregation through the use of areas differing in slope gradient. Most guanacos and vicuñas were foraging when spotted. The proportions of individuals engaged in foraging, resting and walking were, however, different between the two species, the percentage of guanacos grazing (94%) being particularly high in comparison with vicuñas (69%). Vicuña activity pattern varied throughout the day. They were on the move mainly just after midday and rested mainly late in the afternoon. Guanaco group size and pattern of activity showed more variations from other studies than those of vicuña. These differences may be related to the high altitude. In such an area, which lies at the upper limit of their altitudinal range, guanacos may have problems in meeting their energy demands, which are higher than those of vicuñas. Competition between the two species may occur in sympatric areas.     

Caution on the assessment of intestinal parasitic load in studying parasite-mediated sexual selection: The case of Blackbirds coccidiosis

The parasite-mediated sexual selection (PMSS) theory has led to an increasing number of experimental studies essentially focussed on blood parasites. Currently, more research is being carried out on intestinal parasites in relationship to this theory. Before testing the theory with gastrointestinal parasites, it is important: (i) to determine an optimal research methodology to obtain an accurate assessment of parasite burden and (ii) to have information about life-history traits of the parasite to interpret data appropriately. In this study, we present data on oocyst output of Isosporaturdi in the faeces of blackbirds (Turdus merula) that illustrate the importance of developing methods that are relevant for a particular model system, instead of relying on existing methods that may work in other systems. Our results show that: (i) a single droplet of faeces will accurately indicate the parasitic load in blackbirds, (ii) oocyst shedding varies greatly within and between days, (iii) the course of infection is characterised with two successive peaks of oocyst shedding, (iv) infection lasts approximately 1 month and (iv) there is no effect of sex, size of infective dose or re-infection on the course of infection. We discuss the practical implications of these results in determining the reliability of, and in avoiding erroneous conclusions about, PMSS when using intestinal parasites as models. In particular, we emphasise that numerous measurements must be performed on different days. In addition, faeces must be collected at a particular time of day because there is a strong temporal variation in oocyst shedding. Finally, a standardised methodology that has been developed for a particular host-parasite assemblage does not necessarily work with other biological models. Together, our results should encourage future investigators to identify an accurate methodology for assessing parasitic load as a first step before testing hypotheses associated with the PMSS theory.     

Golden hamsters are nocturnal in captivity but diurnal in nature

Daily activity rhythms are nearly universal among animals and their specific pattern is an adaptation of each species to its ecological niche. Owing to the extremely consistent nocturnal patterns of activity shown by golden hamsters (Mesocricetus auratus) in the laboratory, this species is a prime model for studying the mechanisms controlling circadian rhythms. In contrast to laboratory data, we discovered that female hamsters in the wild were almost exclusively diurnal. These results raise many questions about the ecological variables that shape the activity patterns in golden hamsters and the differences between laboratory and field results.     

Diurnal and developmental changes in levels of nucleotide compounds in developing maize endosperms

Maize endosperm is dependent on source tissues to supply the energy and carbon required for development. This supply varies during the course of each day and also throughout development. The impact of these variations on the metabolism of developing endosperm was examined by determining the energy status of the endosperm throughout the course of a day. The adenylate energy charge decreased as the tissue matured, and exhibited a distinct diurnal pattern, reaching a minimum in the afternoon, when the flux of photosynthate is the highest. The minimum value observed was similar to the adenylate energy charge in tissues under mild stress. As the endosperm matured, the adenylate energy charge decreased steadily. The levels of the polysaccharide precursors ADP‐glucose and UDP‐glucose did not reflect the daily fluctuations in adenylate energy charge, but did exhibit similar long‐term behaviour in the latter half of development, decreasing steadily after 21 d after pollination. Similarities in the metabolic patterns of adenylate and uridylate nucleotide levels are discussed in terms of the analogous roles of these compounds in starch and cellulose biosynthesis, respectively. These data provide insight into the metabolic rhythms occurring during endosperm development, and provide a framework for efforts directed toward metabolic engineering.     

Field oviposition rates and egg load dynamics of pollen beetles (Meligethes aeneus Fab.) (Colepotera: Nitidulidae)

Abstract 1 Egg loads from field collected pollen beetles (Meligethes aeneus Fab., Coleoptera: Nitidulidae) were determined by dissecting beetles caught at the beginning and end of the putative daily oviposition period. Field collected beetles were offered Brassica napus (L.) plants in cages for 8 (morning and early afternoon), 16 (overnight), and 24 h to ascertain the number of eggs laid during these time periods. 2 Most eggs were laid in the morning and early afternoon. The proportion of gravid females was higher at the beginning of the oviposition period than at the end. Most females in the morning carried two eggs, whereas one egg was more common in the afternoon. 3 We hypothesized that the number of eggs laid during the oviposition period would be equivalent to the difference between egg loads at the beginning and end of oviposition. This was not the case; differences in egg loads were significantly lower than number of eggs laid. However, the number of eggs laid was equivalent to the egg load at the beginning of the oviposition period, suggesting that eggs available in the morning are laid during the following day. 4 Population estimates of daily oviposition rates, approximately 0.7 eggs per beetle and day, were close to estimates from laboratory studies when the proportion of gravid females was taken into consideration.     

Larval productivity of Fasciola gigantica in two lymnaeid snails

Two groups of Galba truncatula and two groups of Lymnaea natalensis were experimentally infected with Fasciola gigantica to determine if snail species had an influence on the redial burden and cercarial shedding of this trematode when snails of both species were infected with the same isolate of miracidia. In the two groups used for the study of redial burden, the total number of free rediae was significantly higher at day 49 post-exposure in L. natalensis than in G. truncatula. In the groups used for cercarial shedding, the life-span of cercaria-shedding snails and those of infected snails which died without cercarial emission, and the duration of the prepatent period were significantly longer in L. natalensis than those noted in G. truncatula. However, the mean numbers of shed cercariae did not significantly differ and showed no differences in their daily distribution throughout the shedding period. These results demonstrate that G. truncatula might be the principal intermediate host of F. gigantica in Egypt, at least in the areas where this lymnaeid species lives.     

Factors influencing the grazing behaviour of sheep in a Mediterranean climate

The diurnal pattern of grazing of sheep was studied in summer in 2 Mediterranean environments in 3 experiments. In the first experiment with Border Leicester × Merino sheep, it was found that in a given day the times of beginning and ending the major morning and afternoon grazing periods and the time spent grazing, were influenced by time of dawn or dusk, temperature, humidity and the time spent grazing the previous night. The temperature was found to influence the timing of events throughout the day but humidity mainly had an effect in the midday and afternoon.Six breeds of sheep were compared in a second experiment (Romney, Dorset Horn, Cheviot, Suffolk, Southdown and Border Leicester). There were significant differences between the breeds in the diurnal pattern of grazing, in grazing times and in responses to environmental conditions. The Cheviots and Suffolks differed from the other breeds because they began earlier in both the morning and afternoon. The Suffolks grazed for longer in all the grazing periods and differed significantly in grazing time from sheep of all other breeds.In a third experiment, sheep reared in a dry tropical environment (Abydos) behaved differently over 3 summers to sheep raised in a Mediterranean environment with dry summers (Baker's Hill). The main differences were in response to temperature and humidities in the morning and to length of day in the afternoon. The differences diminished with time.Generally, afternoon (pm) activity was more influenced by immediate grazing activity (night grazing time and morning (am) grazing time) than was the morning behaviour, but there were exceptions.     

Chronobiologic Aspects of a Coadaptive Process: The Interaction of Ludwigia elegans Flowers and Their More Frequent Bee Visitors

Field observations spanning 1 year of the visits of two bee species—Tet-raglossula bigamica (Hymenoptera: Colletidae) and Pseudagapostemon brasil-iensis (Hymenoptera: Halictidae)—to the flowers of Ludwigia elegans (Onagra-ceae) evinced the existence of circadian and circannual components in the rhythms of activity both of plant and bees. In addition to morphologic adaptations to the flower, the bees were temporally adjusted to each other and to the flower's opening and closing mechanisms. At the observation locality (Ribeirao Preto, São Paulo, Brazil—latitude 21 °-21 ° 30'S), the plant bloomed year-round. The flowers of the same population open simultaneously at the onset of the photophase, pollen and nectar being available almost immediately. Withering occurs in the afternoon of the same day. Although many bee species visited the flowers, T. bigamica and P. brasiliensis were the most frequent visitors, but their yearly rhythms were phased opposite to one another. Circadian rhythms were detected in pollen and nectar harvest. Comparisons of acrophases showed significant differences for males' and females' nectar collecting rhythm and for females' pollen harvest rhythm. As for the circannual component, acrophases of all rhythms occur at progressively later times from December to July when the migration is reversed until November. These data strongly suggest that the relationship between L. elegans and T. bigamica and P. brasiliensis is in accordance with a clearly temporal pattern and that the two bee species are temporally separated in nature.     

Retinoid and lipid patterns in the blubber of common dolphins (Delphinus delphis): implications for monitoring vitamin A status

We determined retinoid concentrations in various body positions of the blubber of 25 common dolphins (Delphinus delphis) to study topographical variation in concentrations. Specimens were obtained from incidental catches and were apparently healthy. We found concentrations to be high and therefore conclude that blubber represents a significant contribution to total retinoid body load. Consequently, blubber is proposed as a tissue of choice for monitoring retinoid status in this species. Anterior-ventral blubber had the highest vitamin A concentration and posterior-dorsal the lowest. Therefore, when assessing retinoid status, topographical variation should be taken into account to ensure consistent sampling. This pattern appeared to be explained by a parallel variation in lipid content. Thus, the dynamics and body distribution of retinoids appear to be basically governed by the lipophilicity of the molecules. The highest lipid richness found in the anterior-ventral region might indicate that this region is comparatively more important for insulation and lipid storage than the dorsal posterior region. Retinoid levels did not appear to vary according to sex, but they did vary with lipid content. This should be taken into account when designing sampling protocols; for monitoring purposes, biopsies from healthy, free-ranging individuals should be preferred to samples from stranded animals.     

Accidents in children do not happen at random: predictable time-of-day incidence of childhood trauma

In a prospective study, 15,110 childhood traumas were recorded by the Pediatric Surgery Service (CHUV, Lausanne) between January 1, 1990 and December 31, 1997. The exact clock hour when the injury occurred and other germane data were obtained. Time series thus obtained were analyzed by several statistical (ANOVA, cosinor, χ², Table Curve, etc.) methods. High statistically significant circadian patterns were detected with a trough at night—almost no traumas/hour (t/h), and a peak in the afternoon (∼16:00h)—9.3±0.4 (SD) t/h. Such 24h variation was validated for the whole sample for the entire 8yr study span as well as the data of each year. Neither gender- nor age-related differences in the 24h pattern were detected between children under 5 yr of age, who have not yet attended school and children from 5 to 16 yr of age, who attend school. Small but statistically significant differences in the 24h patterns were observed when categorized by the type of activity associated with the trauma and the place of trauma occurrence. The great stability of the 24h pattern in childhood trauma over the 8yr study span suggests an endogenous origin in addition to the role presumably played by environmental factors. Periods of 12 and 8 h were also detected in the time series. The afternoon peak time of childhood traumas differs from that of adults, which is located ∼04:00h in rotating shift workers and automobile drivers and 06:00-08:00h in adult day-workers. The validation of a circadian pattern in childhood traumas with an afternoon peak should be taken into account in the design of children's preventative injury programs.     

Daily and seasonal variation in the haul-out behavior of the South American sea lion

In the South American sea lion (Otaria flavescens), daily fluctuations in abundance have been analyzed based on sequential counts of the number of animals hauled-out. However, no studies have analyzed haul-out activity in relation to an annual cycle or according to different age/sex classes. The objective of this study was to determine the daily and seasonal haul-out patterns of each age/sex class of South American sea lions as a function of the time of the day. A total of 222 days were analyzed in a breeding colony of Chile, from May 2008 to December 2010. During the non-breeding season (March to December) males, females, and juveniles showed a unimodal pattern, in which few sea lions are hauled-out in the morning and maximum numbers are found in the rookery during the early afternoon (1330–1630). In contrast, during the breeding season (austral summer) the proportion of individuals hauled-out shifted from a unimodal to a bimodal pattern, especially in the case of juveniles. Our results indicate that there are fine scale differences in haul-out behavior among age/sex classes, as well as larger scale seasonal differences in the proportion of sea lions ashore. These differences appear to be related to reproductive activities, food availability and thermoregulatory requirements. These patterns of seasonal variability of South American sea lion haul-out should be taken into consideration when planning surveys to estimate population abundance.     

INTERNAL TEMPORAL ORDER IN THE CIRCADIAN SYSTEM OF A DUAL-PHASING RODENT,THE OCTODON DEGUS

Daily rhythms in different biochemical and hematological variables have been widely described in either diurnal or nocturnal species, but so far no studies in the rhythms of these variables have been conducted in a dual-phasing species such as the degus. The Octodon degus is a rodent that has the ability to switch from diurnal to nocturnal activity under laboratory conditions in response to wheel-running availability. This species may help us discover whether a complete temporal order inversion occurs parallel to the inversion that has been observed in this rodent's activity pattern. The aim of the present study is to determine the phase relationships among 26 variables, including behavioral, physiological, biochemical, and hematological variables, during the day and at night, in diurnal and nocturnal degus chronotypes induced under controlled laboratory conditions through the availability of wheel running. A total of 39 male degus were individually housed under a 12:12 light-dark (LD) cycle, with free wheel-running access. Wheel-running activity (WRA) and body temperature (Tb) rhythms were recorded throughout the experiment. Melatonin, hematological, and biochemical variables were determined by means of blood samples obtained every 6?h (ZT1, ZT7, ZT13, and ZT19). In spite of great differences in WRA and Tb rhythms between nocturnal and diurnal degus, no such differences were observed in the temporal patterns of most of the biological variables analyzed for the two chronotypes. Variation was only found in plasma urea level and lymphocyte number. A slight delay in the phase of the melatonin rhythm was also observed. This study shows the internal temporal order of a dual-phasing mammal does not show a complete inversion in accordance with its activity and body temperature pattern; it would appear that the switching mechanism involved in the degu's nocturnalism is located downstream from the pacemaker. (Author correspondence: angerol@um.es).     

Are long‐distance migrant passerines faithful to their stopover sites?

Long-distance migrant passerines are well known to often display high levels of philopatry to breeding and wintering grounds. One could expect that similar selective pressures and similar navigation skills would result in their being faithful to stopover sites, a pattern that has been described for several populations of migratory waders and waterfowl. In this paper, we develop the argument that passerines should suffer from higher costs and receive lower benefits from stopover site faithfulness than waterfowl and waders. Based on Alerstam's (1979) "optimal drift strategy" theory and other considerations, we predict that passerines should have lower stopover site fidelity than geese and waders, and that site faithfulness should decrease with increasing distance from either end of the migratory journey. We present results from a long-term study on the stopover ecology of migrant passerines in southern Portugal that support these predictions and show that, for species and populations that neither nest nor winter in this country, few individuals are faithful to the stopover site. On the other hand, populations that included individuals at (or near to) the start or the end of the migratory journey, had much higher return rates. We could not find any evidence that species linked to scarce habitats, such as wetlands, were more site faithful. Our results are in agreement with several other reports, but in apparent contrast to previous conclusions resulting from some studies involving Old World warblers. These differences are discussed and it is argued that there is no solid evidence to suggest that site fidelity should be important for passerines at stopovers far away from breeding or wintering grounds, meaning that there is a large within-individual variability in the precise migratory routes and stopover sequence used each year.     

Stomatal responsiveness to leaf water status in common bean (Phaseolus vulgaris L.) is a function of time of day

Stomatal response to leaf water status was experimentally manipulated by pressurizing the soil and roots of potted common bean plants enclosed in a custom‐built root pressure chamber. Gas exchange was monitored using a whole‐plant cuvette and plant water status using in situ leaf psychrometry. Bean plants re‐opened their stomata upon pressurization, but the extent of re‐opening was strongly dependent on the time of day when the soil was pressurized, with maximum re‐opening in the morning hours and limited re‐opening in the afternoon. Neither leaf nor xylem abscisic acid concentrations could explain the reduced response to pressurization in the afternoon. The significance of this phenomenon is discussed in the context of circadian rhythms and of other recent findings on the ‘apparent feed‐forward response’ of the stomata of some species to vapour pressure deficit.