Daylight Period Research Articles

Thermoregulatory and Feeding Behavior under Different Management and Heat Stress Conditions in Heifer Water Buffalo (Bubalus bubalis) in the Tropics.

Simple SummarySilvopastoral systems can modulate the thermoregulatory behavior of buffaloes decreasing the heat stress and improving the animal welfare in the tropics. The objective of this study was to compare the behavior of heifer buffaloes in a silvopastoral systems with Leucahena leucocephala trees and a conventional system without trees under two heat stress condition (intense heat stress and moderate heat stress) in Cuba. The results show that despite intense heat stress conditions, the animals spent more time feeding in the silvopastoral system than in the conventional system. Besides, the silvopastoral system reduced the use of water in the wallowing areas. We conclude that pastures with trees increase fodder offer while improve grazing behavior and animal welfare for buffalo farming in tropical conditions. In the wake of climate change and global warming, the production systems of water buffaloes (Bubalus bubalis) are receiving increasing attention in the tropics, where the silvopastoral systems can improve animal welfare and production conditions. The objective of this study was to characterize the behavior of heifer buffaloes in a silvopastoral system (SPS) with Leucaena leucocephala (600 trees/ha) and in a conventional system (CVS), under intense heat stress and moderate heat stress in Cuba. We observed nine animals, with an average weight of 167.9 kg at the beginning of the study, during the daylight period, from 6:00 to 18:00 h, at 10 min intervals, for 12 days. Activities recorded were grazing, ingestion of tree leaves, rumination, water intake, walking, lying, standing, sheltering in the shade of trees, and wallowing. Sheltering in the shade of trees and wallowing were collectively considered as thermoregulatory behavior (TB). TB was different in both systems and conditions of heat stress (p < 0.05), with 4.06 in CVS and 3.81 h in SPS in the intense heat stress period, while it was 2.91 and 1.08 h for SPS and CVS, respectively, during the moderate heat stress period. The wallowing activity showed statistically significant differences (p < 0.05) in the intense heat stress season with 1.18 and 2.35 h for SPS and CVS, respectively. Time spent on feeding behavior was highest in the SPS system (p < 0.05). Longer times of thermoregulatory and feeding behavior indicate the importance of trees in animal welfare for this species in tropical conditions, thus supporting avoided deforestation and the replanting of trees in existing production systems and landscapes.

Reproduction of the sea urchin Tripneustes depressus (Camarodonta: Toxopneustidae) in Bahía de La Paz, Baja California Sur, Mexico

Introduction: Sea urchin gonads (roe or uni) are considered a culinary delicacy worldwide. However, only a few species are considered edible and commercialized. The sea urchin Tripneustes depressus has generated the interest of producers in Baja California Sur, Mexico, due to the quality of its gonads. A biological basis for designing a management strategy is key to consider its commercial exploitation. Objective: To determine the reproductive season of T. depressus through description of the gonad stages and reproductive cycle, and to establish its relationship with environmental factors. Methods: We collected monthly samples (October 2016-September 2017), recording in-situ temperature and photoperiod. We evaluated a sample of 1 055 specimens for demographic characteristics, using total weight (g) and test diameter (cm). We also did a histological analysis of gonads from 178 individuals. Results: Average test diameter was 9.70 ± 0.03 cm (5-12.50 cm). Based on the proportion into the gonad of sexual (gametes) and somatic (nutritive phagocytes) cells, we propose five gonad stages (growing, premature, mature, spawning, and intergametic) for both sexes. There were two times of the year when gonads were heaviest and closely corresponded to the growing stage, coinciding with the highest proportions of nutritive phagocytes. Gonad development (growing and premature stages) peaks in the months with the longest daylight periods, with spawning in the shortest daylight periods. Conclusions: Gonad wet weight and adjusted gonad weight are good indicators of the reproductive season of T. depressus. The lowest gonad wet weights were matched the spawning peak in the shortest daylight period (January and March).

Males and ephippial females of Oriental Chydoridae (Cladocera: Anomopoda) from Cat Tien National Park, South Vietnam.

Cladocera (Crustacea: Branchiopoda) of South-East Asia have been intensively investigated over the last decades, but males and ephippial females of many taxa remain unknown or poorly studied. Males and ephippial females of ten species of Chydoridae were collected by monthly sampling of eight water bodies during autumn-winter dry season in Сat Tien National Park, South Vietnam. Morphology of studied specimens is described and taxonomic status of studied species is discussed. Gamogenetic specimens were sparse in all studied taxa, contributing less than 8 % of the populations in samples. Gamogenetic specimens were found mostly during December-January, what suggests that daylight period is the main factor inducing a sexual reproduction in most studied species.

Modelling and pH Control in Raceway and Thin-Layer Photobioreactors for Wastewater Treatment

One of the most critical variables in microalgae-related processes is the pH; it directly determines the overall performance of the production system especially when coupling with wastewater treatment. In microalgae-related wastewater treatment processes, the adequacy of pH has a large impact on the microalgae/bacteria consortium already developing on these systems. For cost-saving reasons, the pH is usually controlled by classical On/Off control algorithms during the daytime period, typically with the dynamics of the system and disturbances not being considered in the design of the control system. This paper presents the modelling and pH control in open photobioreactors, both raceway and thin-layer, using advanced controllers. In both types of photobioreactors, a classic control was implemented and compared with a Proportional–Integral (PI) control, also the operation during only the daylight period and complete daily time was evaluated. Thus, three major variables already studied include (i) the type of reactors (thin-layers and raceways), (ii) the type of control algorithm (On/Off and PI), and (iii) the control period (during the daytime and throughout the daytime and nighttime). Results show that the pH was adequately controlled in both photobioreactors, although each type requires different control algorithms, the pH control being largely improved when using PI controllers, with the controllers allowing us to reduce the total costs of the process with the reduction of CO2 injections. Moreover, the control during the complete daily cycle (including night) not only not increases the amount of CO2 to be injected, otherwise reducing it, but also improves the overall performance of the production process. Optimal pH control systems here developed are highly useful to develop robust large-scale microalgae-related wastewater treatment processes.

Waveguide photoreactor enhances solar fuels photon utilization towards maximal optoelectronic \u2013 photocatalytic synergy

A conventional light management approach on a photo-catalyst is to concentrate photo-intensity to enhance the catalytic rate. We present a counter-intuitive approach where light intensity is distributed below the electronic photo-saturation limit under the principle of light maximization. By operating below the saturation point of the photo-intensity induced hydroxide growth under reactant gaseous H2+CO2 atmosphere, a coating of defect engineered In2O3-x(OH)y nanorod Reverse Water Gas Shift solar-fuel catalyst on an optical waveguide outperforms a coated plane by a factor of 2.2. Further, light distribution along the length of the waveguide increases optical pathlengths of the weakly absorptive green and yellow wavelengths, which increases CO product rate by a factor of 8.1-8.7 in the visible. Synergistically pairing with thinly doped silicon on the waveguide enhances the CO production rate by 27% over the visible. In addition, the persistent photoconductivity behavior of the In2O3-x(OH)y system enables CO production at a comparable rate for 2 h after turning off photo-illumination, enhancing yield with 44-62% over thermal only yield. The practical utility of persistent photocatalysis was demonstrated through outdoor solar concentrator tests, which after a day-and-night cycle showed CO yield increase of 19% over a day-light only period.

238 Reproductive and lactation management for year-round ewe milk production with non-traditional dairy breeds

Abstract The ability of Finnsheep x Dorset meat ewes to achieve high milk yields in short and frequent 73-day lactation periods on the STAR accelerated lambing system in a year-round dairy system was tested together with ewe reproductive success. Ewes (n = 53) were managed in 3 groups and enrolled in a triply replicated (for management group) 3′3 Latin square design (3 pens, 3 lactations, 3 diets). Diets (L-SH, M-SH, H-SH) contained 31.6, 36.3, 40.0% aNDFom and 41.3, 37.2, 31.9% NFC. Milk was recorded at each 2X milking, ewes and lambs weighed weekly. Ewes were bred to lamb with 219-day lambing intervals. To facilitate breeding, progesterone CIDRs were employed for 7 days prior to breeding during increasing day-light period breeding months. Individual lactation curves were fitted to 127 evaluated lactations. Lactation parameters were analyzed with a model including Square Number, Pen and Lactation within Square Number, and Diet, with 3 to 6 ewes in each cell of each Latin Square. Ewes offered the M-SH diet produced more (P = 0.03) milk/d (1.40, 1.58, and 1.37 ± 0.07 kg) and higher (P = 0.02) lactation yields (95.8, 109.6, and 93.0 ± 5.29 kg), compared with ewes offered the L-HS or H-SH diets, respectively. Investigating the effect of breeding season (January, March, June, August, and October) on reproductive success, conception rates ranged between 83.3 and 94.1% and were not affected by breeding season. Litter sizes were lower for matings in March and June (P &amp;lt; 0.05) compared to June, August, and October. Average daily gains of lambs raised artificially ranged between 283 and 328 g ± 11.2 g per day and were significantly higher for January-born lambs than for March born lambs (P &amp;lt; 0.001). Both milk production and reproductive success were high for ewes milked year-round in short and frequent lactations.

SEASONAL DYNAMICS OF ENDOCRINE REGULATION OF METABOLIC RATE, BLOOD OXYGEN TRANSPORT SYSTEM AND PHYSICAL PERFORMANCE OF MIDDLE OB REGION ATHLETES FROM CYCLIC WINTER SPORTS

Aim. The paper aims to study the seasonal dynamics of endocrine regulation of metabolic rate, blood oxygen transport system and physical performance of Middle Ob region athletes from cyclic winter sports. Materials and methods. A comprehensive two-stage study of the endocrine system, blood oxygen transport system and physical performance was carried out among elite cross country skiers and biathletes aged from 15 to 18 years during the periods of the year with pronounced daylight variability. The research methods included enzyme-linked immunoassay (ELISA) with the measurements of total triiodothyronine, total thyroxine, thyroid-stimulating hormone, total testosterone and growth hormone; analysis of peripheral blood with the measurements of red blood cells, hemoglobin, hematocrit and red blood cell indices; cardiopulmonary exercise testing with ergospirometry and assessment of maximum oxygen consumption, physical work capacity, oxygen pulse and anaerobic threshold. Results. Statistical analysis revealed significant (p &lt; 0.05) seasonal changes in the endocrine system, blood oxygen transport system and physical performance of Middle Ob region athletes. Namely, during the short daylight period there was a significant increase in total triiodothyronine and cortisol, a decrease in total testosterone, red blood cells, hemoglobin, hematocrit and the average volume of red blood cells, an increase in absolute and relative values of maximum oxygen consumption, oxygen pulse, physical work capacity and a decrease in anaerobic threshold. Conclusion. The results of the research characterize the features of athletes’ adaptation to specific climatic factors of the Northern region against the background of intense physical exertion.

An extreme marine environment: a 14-month record of temperature in a polar tidepool

Tidepools are not uncommon in Antarctica, but there appear to be no data on the physical environment within polar tidepools and only anecdotal information on their biology. Here we report a high resolution record of temperature in an Antarctic tidepool made over two summers and the intervening winter. During the summer open water season the highest daily mean, and also the maximum temperatures, were recorded during the period of continuous daylight around the summer solstice. This short-term variability of temperature in the tidepool greatly exceeded that in the nearby open ocean, indicating the need for a eurythermal physiology in tidepool biota. In winter the tidepool froze over, the unfrozen water cooled to − 5.5 °C, and freeze concentration increased its salinity to roughly three times normal seawater. A polar tidepool isolated from the sea in winter is probably inimical to many larger marine organisms, which must populate the tidepool afresh each summer.

Light/heat effects on RNA editing in chloroplast NADH-plastoquinone oxidoreductase subunit 2 (ndhB) gene of Calotropis (Calotropis procera)

BackgroundRNA editing is common in terrestrial plants, especially in mitochondria and chloroplast. In the photosynthesis process, NAD dehydrogenase plays a very important role. Subunit 2 of NADH-dehydrogenase is one of the major subunits in NAD dehydrogenase complex. Using desert plant Calotropis (Calotropis procera), this study focuses on the RNA editing activity of ndhB based on light time. ResultsNdhB (NADH-dehydrogenase subunit 2) gene accession no. MK144329 was isolated from Calotropis procera genomic data (PRJNA292713). Additionally, using RNA-seq data, the cDNA of the ndhB gene of C. procera was isolated at three daylight periods, i.e., dawn (accession no. MK165161), at midday (accession no. MK165160), and pre-dusk (accession no. MK165159). Seven RNA editing sites have been found in several different positions (nucleotide no. C467, C586, C611, C737, C746, C830, and C1481) within the ndhB coding region. The rate of these alterations was deferentially edited across the three daylight periods. RNA editing rate of ndhB gene was highest at dawn, (87.5, 79.6, 78.5, 76, 68.6, 39.3, and 96.9%, respectively), less in midday (74.8, 54.1, 62.6, 47.4, 45.5, 47.4, and 93.4%, respectively), and less at pre-dusk (67, 52.6, 56.9, 40.1, 40.7, 33.2, and 90%, respectively), also all these sites were validated by qRT-PCR. ConclusionThe differential editing of chloroplast ndhB gene across light periods may be led to a somehow relations between the RNA editing and control of photosynthesis.

Daylight autonomy improvement in buildings at high latitudes using horizontal light pipes and light-deflecting panels

Horizontal light pipes (HLP) have shown the potential to convey daylight deeper into buildings. The wide variation in incident angles of sunlight rays and the resulting numerous interreflections of light rays within the pipe are the main reasons for the limited light transmittance of such light pipes during certain daylight periods. This paper presents a research study on different configurations of acrylic laser-cut panels (LCP) applied at the entrance of horizontal pipes as light collectors to increase the transmittance of HLPs and improve daylight autonomy in spaces equipped with HLPs. This study required the development of a suitable methodology. The study begins with an experimental laboratory test of a HLP scale model to determine the light transmittance efficiency (standard daylight guide characteristic) of HLPs with several LCP configurations. The results from the laboratory test are combined with the statistical data for both the direct and diffuse illuminance on the vertical south-oriented surface (Satel-Light database) for the location selected for the analyses (Oslo, Norway). The analyses are discussed via the application of a theoretical model of an office space equipped with a HPL as well as through the concept of daylight autonomy (DA) in an indoor space. The paper shows that a certain static LCP configuration has the potential to increase DA100 and DA300 to 10% and 19%, respectively, at a 2.1 m distance from the façade, and 8.75% and 16%, respectively, at a 4.5 m distance. This paper also contributes to lighting science with its data on the light transmittance efficiency of each LCP configuration, which can be applicable in further research.

Trophic Dynamics of Zooplankton Before and After Polar Night in the Kongsfjorden (Svalbard): Evidence of Trophic Position Estimated by δ15N Analysis of Amino Acids

In polar ecology, zooplankton diets and survival rates vary according to the seasonality of solar radiation and oceanographic conditions. Each zooplankton species has evolved feeding strategies to survive in the diet-limited conditions of the “polar night”. Many zooplankton studies have reported seasonal adaptations in feeding activity during polar night based on their trophic niches. Nitrogen isotope analysis of amino acids has provided improved accuracy in estimates of trophic position (TP) in various marine species. In this study, field work was conducted in Kongsfjorden before (October 2017) and after polar night (April 2018). As representative zooplankton, an amphipod (Themisto abyssorum), euphausids (Meganycitiphanes norvegica and Thysanoessa sp.), a chaetognath (Parasagitta elegans), and copepods (Calanus spp. and Oithona similis) were collected. TP values of each taxon were estimated using the nitrogen isotope ratio of glutamic acid (δ15NGlu) and phenylalanine (δ15NPhe). Results showed that TP values of P. elegans were relatively constant, averaging 3.2 in both seasons, likely due to continuous feeding activity during polar night. TP values were also constant for Calanus spp., ranging 2.5 to 3.0 in both seasons due to the ability to utilize stored high-energy wax. In contrast, average TP values for O. similis, an omnivorous zooplankton, were 2.9 in October and 2.3 the following April. TP values for O. similis before polar night can be attributed to the relatively high availability of algae during longer periods of daylight. We found that TP variation in zooplankton before and after polar night differed according to feeding activities in diet-restricted circumstances.

An application of upscaled optimal foraging theory using hidden Markov modelling: year-round behavioural variation in a large arctic herbivore

BackgroundIn highly seasonal environments, animals face critical decisions regarding time allocation, diet optimisation, and habitat use. In the Arctic, the short summers are crucial for replenishing body reserves, while low food availability and increased energetic demands characterise the long winters (9–10 months). Under such extreme seasonal variability, even small deviations from optimal time allocation can markedly impact individuals’ condition, reproductive success and survival. We investigated which environmental conditions influenced daily, seasonal, and interannual variation in time allocation in high-arctic muskoxen (Ovibos moschatus) and evaluated whether results support qualitative predictions derived from upscaled optimal foraging theory.MethodsUsing hidden Markov models (HMMs), we inferred behavioural states (foraging, resting, relocating) from hourly positions of GPS-collared females tracked in northeast Greenland (28 muskox-years). To relate behavioural variation to environmental conditions, we considered a wide range of spatially and/or temporally explicit covariates in the HMMs.ResultsWhile we found little interannual variation, daily and seasonal time allocation varied markedly. Scheduling of daily activities was distinct throughout the year except for the period of continuous daylight. During summer, muskoxen spent about 69% of time foraging and 19% resting, without environmental constraints on foraging activity. During winter, time spent foraging decreased to 45%, whereas about 43% of time was spent resting, mediated by longer resting bouts than during summer.ConclusionsOur results clearly indicate that female muskoxen follow an energy intake maximisation strategy during the arctic summer. During winter, our results were not easily reconcilable with just one dominant foraging strategy. The overall reduction in activity likely reflects higher time requirements for rumination in response to the reduction of forage quality (supporting an energy intake maximisation strategy). However, deep snow and low temperatures were apparent constraints to winter foraging, hence also suggesting attempts to conserve energy (net energy maximisation strategy). Our approach provides new insights into the year-round behavioural strategies of the largest Arctic herbivore and outlines a practical example of how to approximate qualitative predictions of upscaled optimal foraging theory using multi-year GPS tracking data.

Modelling and simulation of the power subsystem of a low earth orbit CubeSat

Modelling and simulating power subsystems of CubeSats are important tools in research and satellite design. To enhance the reliability of a CubeSat, a power subsystem simulator has been furnished. Statistical process control (SPC) is used to perform post-simulation analysis to detect faults in the system. This paper presents an architectural template for a simple power subsystem of CubeSat missions. The simulator has a modular structure with mathematical models of batteries, solar arrays, and the power control unit (PCU). This simulation helps with preliminary sizing and configuration of selected electrical components in an unregulated bus voltage scenario. The solar arrays, batteries, and PCU are modelled using a current–voltage lookup table, a voltage-capacity lookup table, and repeating sequences, respectively. The design is adapted to simulate the power subsystem of ManitobaSat-1, a student CubeSat built as part of the Canadian CubeSat Project. Batteries and solar cells are well sized to supply the necessary power during daylight and eclipse period using lookup tables and conditional switches. Outputs from this model will be used by the SPC module to detect out of control conditions as the simulation will describe the baseline or “normal” behaviour. Its application with the SPC module in automating satellite communications is discussed. This simulator is easily applicable to any satellite mission by modifying a few design parameters. It provides a feasible, user-friendly, simple and easily modifiable interface to perform complex analysis.

How the effects of latitude on daylight availability may have influenced the evolution of migration and photoperiodism

Abstract Date and latitude interact to determine photoperiod, the daily period of daylight. This interaction has important implications for latitudinal migrants for whom daylight may be a resource or for whom photoperiod regulates annual transitions in life‐history stages (i.e. birds). Using an established formula, we developed user‐interactive, animated models that enable the visualization of how latitude and date determine photoperiod for latitudinal migrants. We also calculated the photoperiodic schedules for a broad range of hypothetical migratory programmes and real migratory programmes newly available through the proliferation of citizen‐science data. This enabled us to infer the limitations some migratory programmes place on mechanisms for photoperiodic regulation of annual breeding. In the vast majority of cases, the act of migrating elevates annual daylight exposure. This raises the hypothesis that daylight availability selects for latitudinal migration, potentially contributing to its evolution in animals such as diurnal birds with limited time during the spring and summer to feed young. However, photoperiodic mechanisms regulating annual cycles could constrain the evolution of such migrations, depending on how they affect photoperiodic schedules. Most migratory programmes are consistent with known mechanisms of avian photoperiodism, but the range of feasible mechanisms declines for transequatorial migrants, which experience semi‐annual, 180°‐phase‐shifts in their photoperiodic cycles. Understanding photoperiodic constraints on migration is particularly important in this age of changing latitudinal distributions and phenologies driven by climate change. A free Plain Language Summary can be found within the Supporting Information of this article.

Food anticipatory circadian rhythms in mice entrained to long or short day photoperiods

Food anticipatory activity (FAA) rhythms that emerge in nocturnal rodents fed once daily are mediated by food-entrainable circadian oscillators (FEOs) located outside of the suprachiasmatic nucleus (SCN), the site of a circadian pacemaker required for entrainment to daily light-dark (LD) cycles. Specification of the neural and molecular substrates of FEOs driving FAA is complicated by homeostatic, hedonic and environmental factors that can modulate expression of activity independent of circadian timing. Here, we examined the effect of photoperiod (duration of the daily light period) on FAA in mice fed during the last 4 h or middle 4 h of the light period for at least 5 weeks. Long photoperiods decrease SCN pacemaker amplitude, which may favor expression of FAA during the day, when the SCN normally opposes activity in nocturnal rodents. To test this prediction, in Experiment 1, mice housed with or without running discs were entrained to 24 h LD cycles with 8 h (L8) or 16 h (L16) photoperiods. When food was restricted to the last 4 h of the light period (late-day), mice housed with running discs showed more FAA in L16, whereas mice without running discs showed more FAA in L8. In Experiment 2, mice were entrained to L8 or L16 photoperiods, and the 4 h daily meal was centered in the light period (mid-day). FAA was decreased relative to late-day fed mice, but did not vary by photoperiod. In Experiment 3, mice with or without running discs were entrained to L12 or L18 photoperiods, with mealtime centered in the light period. FAA again did not differ between photoperiods. In constant dark (DD) prior to food restriction, the period (τ) of free-running rhythms was shorter in mice entrained to long days. This known after-effect of photoperiod on τ was absent in DD immediately following restricted feeding. The phase of LD entrainment, unmasked on the first day of DD with food ad-libitum, was significantly advanced in mice from the late-day feeding schedule, compared to mice from the mid-day schedules. These results indicate that FAA in mice does not vary systematically with photoperiod, possibly because daytime feeding schedules attenuate the effect of photoperiod on the mouse SCN pacemaker. FAA in the present study was more strongly influenced by running disc availability and by meal time within the light period, possibly due to effects on LD entrainment, which was phase advanced by late-day but not midday feeding.

Seasonal Dynamics of Lipids and Their Fatty Acids in Leaf Buds of Betula pendula Roth and Alnus alnobetula subsp. fruticosa (Rupr.) Raus under Conditions of the Cryolithozone

Absolute and relative content and composition of fatty acids, total lipids, and phospholipids, as principal constituents of cell membranes, were examined on vegetative buds of deciduous trees and shrubs throughout the summer and autumn–winter seasons under climatic conditions of the cryolithozone of Yakutia. Lipid metabolism was found to play an essential role in plants' adaptation to low autumnal and winter temperatures in the permafrost zone of Yakutia. The content of phosphatidylcholine in leaf buds of the birch Betula pendula Roth and the shrub Alnus alnobetula subsp. fruticosa (Rupr.) Raus increased throughout the observation period from 9.9 to 23.4 mg/g dry wt. In the autumn–winter period, the composition of fatty acids in the bud lipids of both species was characterized by a high content of unsaturated C18:2 and C18:3 acids. Biosynthesis of fatty acids in buds of deciduous trees and shrubs at a low temperature was apparently controlled by ω3-desaturase, whose activity elevated the content of α-linolenic acid from 2.9 to 5.7 mg/g in B. pendula and from 1.6 to 4.8 mg/g dry wt in A. alnobetula subsp. fruticosa. The seasonal decrease in air temperature was accompanied by an increase in the unsaturation coefficient (k) from 0.9 to 2.3 in B. pendula and from 1.4 to 1.8 in A. alnobetula subsp. fruticosa. It is proposed that the high content of polyunsaturated fatty acids in the autumn–winter period in vegetative buds of the examined woody plants is determined by a complex of climatic factors of the permafrost zone, such as a sharply contrasting day and night temperatures during plant dormancy, extremely low air temperature in winter (down to –60°С), and a short daylight period at this time of the year.

Nocturnal mother–juvenile offspring interaction at the beginning of the juvenile period in free-ranging spider monkeys (Ateles geoffroyi): a report on two cases

The objective of this study was to describe the nocturnal behavior patterns of the interaction between mothers and their juvenile offspring at the beginning of the juvenile period in two dyads of free-ranging spider monkeys (Ateles geoffroyi). Based on direct field observation, we recorded six interaction behaviors between mothers and their juvenile offspring at nighttime and during the daylight period. The frequencies and proportions of each behavior recorded were analyzed for both conditions, and qualitative descriptions of each behavior were made. Observations revealed that the percentage of proximity in the dyads tended to increase at nighttime compared to the daylight period. In one of the dyads, we observed that the percentage of grooming also showed an upward tendency at nighttime compared to the daylight period. The dyads remained together to sleep during all 8 days of the study and were seen to seek arm-in-arm contact and to perform grooming behaviors. Our results suggest that mother–juvenile interaction at the onset of the juvenile period in spider monkeys may be characterized by greater proximity and social grooming behaviors, while the nocturnal observations suggest a strong attachment between mothers and their juveniles in this stage.

Association between circadian Holter ECG changes and sudden cardiac death in patients with Chagas heart disease

Objective: Chagas disease (ChD) is a parasitic illness, largely spread over South America. ChD usually causes progressive myocardium damage, either by direct parasite action or through autoimmune response. Sudden cardiac death (SCD) is prevalent in the early disease stages, being associated with a high variety of ectopic cardiac beats. This study aims at applying heart rate variability (HRV) and heart rate turbulence (HRT) techniques over Holter electrocardiogram (ECG) records to investigate the association with SCD in Chagas heart disease (ChHD). Approach: From a retrospective evaluation of a local database, the Holter records from 78 outpatients (34 female) were divided into groups: SCD deaths (20) and alive patients (56). To consider circadian autonomic changes, the analysis was performed in three periods: (a) entire 24 h record, (b) 12 h daylight period, and (c) the remaining 12 h including night rest. Eight variables were extracted using HRV and HRT approaches from each record and analysed together with the left ventricular ejection fraction (LVEF) estimated by echocardiography. Main results: The set of parameters was reduced by both the forward- and backward-stepwise approach and classification was performed using the k-nearest neighbours method and a leave-one-out cross-validation in a set of ten bootstrap trials, where SCD data were randomly taken and repositioned to balance the groups. The best 24 h model predicted SCD with 89.9% ± 0.9% accuracy using three HRV variables. The use of 12 h segments increased the accuracy up to 91.0% ± 1.2% in a model with the standard deviation parameter measured during the day (SDNNday) and night (SDNNnight). Although considered as playing a major role in SCD, LVEF did not show an association with SCD in this sample. Significance: The degree of HRV and its circadian changes are associated with SCD in ChHD patients.

The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears.

Life in the Arctic presents organisms with multiple challenges, including extreme photic conditions, cold temperatures, and annual loss and daily movement of sea ice. Polar bears (Ursus maritimus) evolved under these unique conditions, where they rely on ice to hunt their main prey, seals. However, very little is known about the dynamics of their daily and seasonal activity patterns. For many organisms, activity is synchronized (entrained) to the earth's day/night cycle, in part via an endogenous (circadian) timekeeping mechanism. The present study used collar-mounted accelerometer and global positioning system data from 122 female polar bears in the Chukchi and Southern Beaufort Seas collected over an 8-year period to characterize activity patterns over the calendar year and to determine if circadian rhythms are expressed under the constant conditions found in the Arctic. We reveal that the majority of polar bears (80%) exhibited rhythmic activity for the duration of their recordings. Collectively within the rhythmic bear cohort, circadian rhythms were detected during periods of constant daylight (June-August; 24.40 ± 1.39 h, mean ± SD) and constant darkness (23.89 ± 1.72 h). Exclusive of denning periods (November-April), the time of peak activity remained relatively stable (acrophases: ~1200-1400 h) for most of the year, suggesting either entrainment or masking. However, activity patterns shifted during the spring feeding and seal pupping season, as evidenced by an acrophase inversion to ~2400 h in April, followed by highly variable timing of activity across bears in May. Intriguingly, despite the dynamic environmental photoperiodic conditions, unpredictable daily timing of prey availability, and high between-animal variability, the average duration of activity (alpha) remained stable (11.2 ± 2.9 h) for most of the year. Together, these results reveal a high degree of behavioral plasticity in polar bears while also retaining circadian rhythmicity. Whether this degree of plasticity will benefit polar bears faced with a loss of sea ice remains to be determined.

The influence of population-control methods and seasonality on the activity pattern of wild boars (Sus scrofa) in high-altitude forests

The wild boar (Sus scrofa) is a problematic invasive species which has colonized the threatened Brazilian Atlantic Forest. Our objective was to evaluate if population control and seasonality affect the circadian rhythm of wild boar activity. Wild boar activity was monitored by camera-traps for 1 year without population-control methods and 1 year with population-control methods implemented in the area. Before population control was implemented, wild boar activity was uniform across 24 h, with animals being active at any given time (cathemeral). After the population control, wild boars concentrated their activities on the daylight period. Also, wild boars were more active during the wet season, possibly influenced by the presence of seeds of Araucaria angustifolia trees. Based on these results, control measures should be conducted during the wet season and different management strategies, such as the use of rifles with telescopic sights and silencers, should be tested.