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Intra-seasonal growth responses of co-occurring European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) to weather variability in montane forests can provide useful information on their future growth trends. To improve growth predictions, we aimed to identify (i) the main seasonal windows during which weather variability influences tree-ring growth, (ii) species-specific differences in the response to weather fluctuations, and (iii) teleconnections to remote sites in the Western Carpathians. We monitored intra-seasonal growth dynamics based on proxies extracted growth signals detected by high-resolution dendrometers in the transition zone between the beech and spruce altitudinal belt. Over 12 consecutive seasons in the natural montane forest (1350 m a.s.l.), the main part of spruce (68% to 10 July) and beech (95% to 26 August) annual increment was under the prevailing influence of temperature. After this, precipitation pattern (regarding spruce) and day length became the most influential variables during deceleration and cessation of growth. In addition, synchronous patterns with remote sites in the Western Carpathians were found. The results emphasize the importance of studying the influence of shorter-term weather fluctuations during the season. Our findings suggest that montane spruce tends to be less temperature-demanding and more drought-sensitive than beech, which may favor beech over the spruce under the future climate.

Information on positional behavior contributes to the understanding of the ecological adaptation mechanisms in animals. We collected data on the positional behavior of white‐headed langurs (Trachypithecus leucocephalus) at the Guangxi Chongzuo White‐Headed Langur National Nature Reserve from September 2016 to August 2017 via instantaneous scan sampling method. This study aimed to examine the importance of positional behavior flexibility in limestone forests characterized by seasonal variations in climate and food resources. Our results indicated that langurs adopted leaping (47.92% ± 5.50%) and vertical climbing (40.13% ± 6.20%) as their predominant locomotor modes and sitting (83.08% ± 4.70%) as their predominant posture. Their positional behavior exhibited marked seasonal variations. More specifically, langurs used quadrupedal walking more frequently during the dry season than during the rainy months. In the stationary state, they sat more frequently during the dry season, whereas they laid and suspended more often during the rainy season. Their positional behavior was affected by fruit availability, day length, and temperature. Quadrupedal walking increased with the decrease in fruit availability, whereas leaping was positively correlated with fruit availability. Moreover, sitting was positively correlated with average temperature but negatively correlated with day length. Lying was also negatively correlated with temperature but positively correlated with day length. We conclude that white‐headed langurs adapt to limestone forests with positional behavior flexibility in response to seasonality. Our research provides evidence of the effects of food availability, ambient temperature, and day length on the positional behavior of white‐headed langurs, highlighting the need to understand their behavioral ecology and the influence of ecological factors on behavioral adaptation., Our research provides evidence of the effects of food availability, ambient temperature, and day length on the positional behavior of white‐headed langurs, highlighting the need to understand their behavioral ecology and the influence of ecological factors on behavioral adaptation.

Parrotfishes are prominent members of the herbivore/detritivore feeding guild on coral reefs. Their feeding activity is important for the removal of algae and detritus, the clearing of new settlement sites for coral and other larvae, and the bioerosion and redistribution of sand across the reef. Estimates of parrotfish feeding activity are normally obtained by divers that may influence or overlook fish behaviors, and are of short duration, limited to shallow habitats, and have limited temporal resolution to associate feeding activity with ecological processes. Excavator and scraper parrotfishes have a robust beak-like jaw morphology that produces a unique sound as the teeth scrape the surface of hard coral rock. We tested the hypothesis that ambient parrotfish bite sounds can be used to estimate their temporal patterns of feeding and associations with environmental variates in the area of an acoustic recorder. Acoustic recorders were deployed on 2 Hawaiian reefs to collect ambient fish sounds for a period of 3 yr. Parrotfish bite sounds showed distinct and repetitive variations in daily, seasonal, and annual feeding patterns, and were statistically correlated with factors of day length and tide range. This study demonstrates the utility of using parrotfish bite sounds to estimate patterns of feeding at coral reef sites. We suggest that regular sampling by multiple acoustic monitors may be a cost-efficient and valuable tool for monitoring the health, degradation, and recovery of large coral reef areas.

In hydropeaking rivers, flow regulation typically follows demands in electricity consumption. One hundred and twenty one adult salmon were tagged with radio transmitters to study their spawning run migration patterns in hydropeaking conditions. The fish were released in small groups into the rivers Kemijoki and Iijoki, in Finland. Typically, salmon made subsequent up‐ and downstream movements ascending upstream to the tailrace of the power station and then descending again downstream to lower water velocities. The rate of these migration attempts was higher in mid‐summer and at relatively high flows. On an hourly basis, the pattern of migration attempts followed a trend of increasing attempts at dawn and higher discharges and a decreasing trend towards dusk and low flows. It was concluded that day length and discharge were the most important environmental factors, while temperature had less effect on the pattern of migration attempts.

In this study, we made monthly assessments of the reproductive phenology of ten cacti species that are widely distributed in the Brazilian Chaco over a 2-year period. We tested whether different climatic regimes in this region promoted the evolution of different reproductive strategies among cacti species. We applied circular statistics and the Rayleigh test to determine whether flowering and fruiting were seasonal and to detect significant periodic patterns. Multiple linear regressions were used to determine the influence climatic variables had on the number of flowers and fruits produced by each species. The flowering and fruiting periods began during the rainy season and peaked in November and January, respectively. Annual and continuous patterns were observed, which presented extended durations. The timing of flowering and fruiting was positively associated with day length and temperature. Rainfall was not significant in any of the models. In the Brazilian Chaco, the cacti reproductive phenophases were triggered by changes in day length and temperature. The similarity in flowering and fruiting patterns among the cacti species with extended durations generated a significant amount of overlap in flowering and fruiting, which may be a strategy to maintain pollinator and seed disperser populations in this environment.

14 pages, 6 figures, 1 table, supplementary material https://www.frontiersin.org/articles/10.3389/fmicb.2020.01590/full#supplementary-material.-- Data Availability Statement. The raw sequence data have been deposited at the National Center for Biotechnology Information (NCBI). The data can be accessed online (https://www.ncbi.nlm) with the code PRJNA345534, Seasonal dynamics of ocean prokaryotic communities in the free-living fraction have been widely described, but less is known about the seasonality of prokaryotes inhabiting marine particles. We describe the seasonality of bacterial communities in the particulate matter continuum by sampling monthly over two years in a temperate oligotrophic coastal ecosystem and using a serial filtration (including six size-fractions spanning from 0.2 to 200 μm). We observed that bacterial communities in the particulate matter continuum had annual changes following harmonic seasonal oscillations, where alpha, beta, and gamma diversity increased during the warm period and decreased during the cold period. Communities in each size-fraction changed gradually over time, being the communities in larger size-fractions the ones with stronger annual changes. Annual community changes were driven mainly by day length and sea surface temperature, and each size-fraction was additionally affected by other variables (e.g., smaller size-fractions by dissolved PO4 and larger size-fractions by turbidity). While some taxonomic groups mantained their preference for a given size fraction during most of the year, others varied their distribution into different size fractions over time, as e.g., SAR11, which increased its presence in particles during the cold period. Our results indicate that the size-fractionation scheme provides novel seasonal patterns that are not possible to unveil by analyzing only free-living bacteria, and that help to better understand the temporal dynamics of prokaryotes, This research was funded by projects STORM (CTM2009-09352), ADEPT (CTM2011-23458), REMEI (CTM2015-70340-R), ANIMA (CTM2015-65720-R), and MIAU (RTI2018-101025-B-I00) funded by the former Spanish Ministries of Science and Innovation, Ministry of Economy and Competitiveness, and now Science, Innovation and Universities. JH was partially supported by the Chilean National Agency for Research and Development (ANID) (FONDECYT-POSTDOCTORADO 3180152). MM was supported by a CSIC JAEPredoc Grant, by the Ministry of Labor, Employment and Social Security of Spain and by the Chilean National Agency for Research and Development (ANID) (FONDAP-IDEAL 15150003 and FONDECYT-POSTDOCTORADO 3190369). The publication fee was supported by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI), Spain, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Flower opening and closure is a crucial process in pollinator attraction. The duration of flower lifespan, the time between flower opening and closure, represents a trade-off between pollinator attraction and the cost of flower maintenance caused by increased respiration and transpiration rates, particularly when ambient temperature is high. Moreover, flower lifespan can decrease rates of autonomous self-pollination. We examined whether flower lifespan in common chicory (Cichorium intybus) is determined by pollinator availability and/or by abiotic factors such as temperature and day length. Plants were investigated in one study site in East Slovakia during the summer and autumn seasons of 2016 and 2019, respectively. Individual flower opening and closure and pollinator availability were recorded during the flowering season and across various hand-pollination treatments including self-pollination, cross-pollination, no pollination and an unmanipulated control. Flower lifespan was positively correlated to time of the season as well as to lower pollinator abundance. Unpollinated flowers remained open for a longer period than self-pollinated, cross-pollinated and control flowers. The time of the season has stronger impact on flower lifespan than the onset of pollination. Findings in this study indicate that seasonal changes characterized by daytime temperature, day length and pollinator availability need to be taken into account in research of flowering time.

Made available in DSpace on 2018-12-11T17:34:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-11-01 Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão Widespread savanna tree species can grow and survive at sites that diverge in water availability and seasonality, thus these species may be able to adjust their phenology in response to site variations. Here we evaluated vegetative and reproductive phenology in five woody species whose populations grow at two savannas sites under divergent climatic regimes, inserted in a large transitional zone between the Amazon forest and the semi-arid region. Patterns of leaf fall, leaf flush and flowering were recorded monthly for five woody species growing under longer (LDS) and shorter (SDS) dry seasons. We evaluated the seasonality, the start and peak dates for phenological events and the associations between phenophases and climatic data. We found a close relationship between phenological events and site temperatures, with phenological peaks in the LDS occurring, in general, about one to three months later than at the SDS site. Leaf fall coincides with warmer and drier periods when the day length is shorter. Leaf production and flowering were associated with increased day length in some populations. Our results support the hypothesis that the conspecific populations have a high degree of association with climatic variables, especially temperature and day length, showing distinct phenological responses associated to the local climatic differences. Universidade Federal do Maranhão Programa de Pós Graduação em Biodiversidade e Biotecnologia − Rede Bionorte Campos Universitário do Bacanga 1966 Instituto Federal de Educação Ciência e Tecnologia do Maranhão Campus Barreirinhas, Barreirinhas Universidade Federal do Maranhão Departamento de Biologia Laboratório de Estudos Botânicos − LEB Campos Universitário do Bacanga 1966 Faculdade de Cências Agrárias e Veterinárias Univ. Estadual Paulista (UNESP), Campus de Jaboticabal Faculdade de Cências Agrárias e Veterinárias Univ. Estadual Paulista (UNESP), Campus de Jaboticabal

In most avian species, egg-turning behavior during incubation is vital for proper embryonic development and hatching success. However, changes in turning behaviors are rarely studied across different temporal scales (e.g., day–night or across incubation phases), though the timing of incubation behaviors affects reproductive success. We used data loggers encapsulated in artificial eggs to measure turning rates and angle changes of eggs in Western Gull (Larus occidentalis) and Laysan Albatross (Phoebastria immutabilis) nests. We examined diurnal and daily cycles in egg-turning behaviors across early, middle, and late incubation phases. Our results indicate that (1) egg-turning behaviors remain similar throughout incubation, resulting in a consistent environment for developing chicks; (2) egg-turning rates and angle changes vary according to diurnal cycles and day length in each species; and (3) egg-turning rates, but not angle changes, were similar between species. Egg-turning behaviors may vary am...

Drought-tolerant crops with high nutritional value such as amaranth leafy vegetables have the potential to improve the diet of rural communities in dry semi-arid areas of southern Mozambique. A study was conducted aiming to assess the vegetative growth and leaf nutritional content of Amaranthus hybridus and A. tricolor when subjected to different watering regimes (80%, 50% and 20% of total available water) during the rainy and dry seasons, and ascertain the relationship between temperature and day length affecting the leaf yield of the two species. Six field trials were conducted in a randomised complete block design with 2 × 3 factorial layout with six replications in Maputo. Vegetative growth was sensitive to soil water at 50% and 20% of available water. However, the leaf and side-shoot number, leaf area and yield were less sensitive to short-interval water deficits during the rainy season. Leaf calcium and crude protein contents were higher at low water levels. Leaf yield was significantly affected by ...

To address the problem of high maturity at 2 years of age among Salvelinus alpinus (Labrador strain), PIT-tagged yearlings (ca. 110 g) were reared for 18 weeks overwinter (Nov. 16 to Apr. 1) under six treatments (90 fish per treatment) that combined three factors: photoperiod (natural day length, LDN or 24 h light, LL), temperature (10 or 5 °C), and food (fed daily or no food). On April 1 all fish were returned to LDN, 10 °C and fed daily for a further six months. In November, the maturity rate was very high among fish reared the previous winter under LDN and fed daily at both 10 °C (♀ 94%, ♂ 43%) and 5 °C (♀ 87%, ♂ 45%). Replacing LDN with LL overwinter, at 10 °C halved the maturity rate (♀ 49%, ♂ 19%), and at 5 °C eliminated maturity among females, and male maturity was 6%. Food deprivation for 18 weeks posed no health problems, and combined with LL also was highly effective at preventing maturation, both at 10 °C (♀ 0%, ♂ 2%) and 5 °C (♀ 0%, ♂ 7%). Compensatory growth following the suppression of growth overwinter indicates this approach to reducing maturity can be a commercially viable means to produce 1 kg immature product around 2 years old. A new two-step gating mechanism is proposed to explain the photoperiod prevention of maturation, one independent of somatic growth, the other dependent. Statement of relevance This study shows that the combination of LL, reduced temperature and food deprivation can significantly reduce the incidence of maturation and improve the productivity among diploid Arctic charr. This combination approach can potentially be applied to other farmed salmonids and non-salmonids to improve the efficacy of controlling sexual maturation.

Made available in DSpace on 2018-12-11T17:02:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-08-01 Seasonal cambial activity was investigated in one- to three-year-old branch modules (branch constructional units) of ten woody species from cerrado sensu stricto, a savanna-like ecosystem, of southern Brazil. Relationships between cambial activity and environmental factors (precipitation, temperature, day length) and leaf production were tested using generalized linear mixed model. Regardless the plant habit and leaf shedding patterns, cambial activity (about 5 months) corresponded to the core of the rainy season (when at least 66% of the annual precipitation had been reached), even though there was some delay or advance in the timing of cambial activity depending on the branch age or species. Cambial activity began in the dry season and ceased before the end of rainy season. Although cambial activity has been positively correlated with day length, precipitation, temperature, and budding for all species, day length, among the assessed factors, seems to be the best predictor of onset and cessation of cambial activity in the branch modules of cerrado species. Univ Estadual Paulista-UNESP Faculdade de Ciências Agronômicas Departamento de Ciência Florestal, Rua José Barbosa de Barros, n 1780 Univ Estadual Paulista-UNESP Instituto de Biociências Departamento de Botânica UNICAMP UNESP USDA Forest Products Laboratory Center for Wood Anatomy Research, One Gifford Pinchot Dr Univ Estadual Paulista-UNESP Faculdade de Ciências Agronômicas Departamento de Ciência Florestal, Rua José Barbosa de Barros, n 1780 Univ Estadual Paulista-UNESP Instituto de Biociências Departamento de Botânica UNESP

Combining radio-telemetry with direct observations, we followed 22 released juvenile captive-bred capercaillies throughout the day to assess if their seasonal and daily patterns of activity, movements, and diet are in accordance with published information on wild birds. Day length was the most important factor determining birds' mobility and activity. Capercaillies were active for 46 ± 2% of daytime, during which they mostly foraged (30 ± 2%). The average distance travelled per day was 0.93 ± 0.14 km. The time budget of capercaillies was mostly allocated to activities on the ground but they spent at least 20% of the daytime in trees. They fed primarily on blueberries, cowberries and pine needles. The mean daily feeding time in fall and winter was 3 h, but it increased to 6 h in spring and summer. We conclude that released birds behave similarly to wild birds and reintroduction of captive-bred capercaillies can be successful if the initial mortality is reduced.

Most studies on springs assumed stability, and reduced seasonal changes in the biota. We focused on two macroalgae (the rhodophyte Hildenbrandia rivularis and the chrysophyte Hydrurus foetidus) to unveil their seasonal-development patterns in springs. H. rivularis cover remained virtually constant throughout the year, although seasonal fluctuations in ecophysiological parameters were detected. The most important determinant of seasonal changes in H. rivularis was shown to be the complex interplay between solar radiation (day length) and shading. Negative cross-correlation between Chl-a and shading was found to be significant but with a time lag. H. foetidus seasonal changes were evident both at the macroscopic level and in ecophysiological parameters. Interestingly, it occurred throughout the year in the spring whilst it completely disappeared in summer in a nearby glacial stream. Unexpectedly, variability of ecophysiological parameters (coefficients of variation) was shown to be 15-20% higher in H. rivularis than in H. foetidus.

Photoperiodism involves the use of both absolute measures of day length and the direction in which day length is changing as a cue for regulating seasonal changes in physiology and behaviour so that birth and lactation coincide with optimal resource availability, increasing offspring survival. Induced ovulation and opportunistic breeding is often found in species that are predominantly solitary and territorial. In this study, the photoperiodic reproductive responses of male greater red musk shrews (Crocidura flavescens (I. Geoffroy Saint-Hilaire, 1827)) were investigated in the laboratory. The presence of spermatozoa regardless of the light cycle, suggest that although the shrews are photoresponsive, they may be capable of breeding throughout the year. Significantly greater testicular volume and seminiferous tubule diameter following exposure to a short day-light cycle suggests that these animals may have breeding peaks that correspond to short days. The presence of epidermal spines on the penis indicates that the shrew is likely also an induced ovulator. Flexible breeding patterns combined with induced ovulation affords this solitary species the greatest chance of reproductive success.

The article contains the results of observations on the formation, existence and the dissociation of the collective winter roost of corvids (crow species) in 2014–2015 in Melitopol (Zaporozhye region). A detailed study of the concentration and the dynamics of its functioning during the winter period was carried out. By the method of absolute counting of birds, the estimation of the gathering process on the roost in the night and dispersal from roost in the morning was carried out twice a week (a total of 47 days of observation in the morning and evening). We selected the following essential parameters: time of the beginning and ending of the process of dispersal from the roost in the morning and gathering at the roost in the evening; time – study of birds’ flight activity in these intervals; the number and species composition of birds; directions of flights with their mapping; weather conditions. Within the city of Melitopol during the winter period of 2014–2015, corvids (Rook, Western Jackdaw, Eurasian Magpie and Common Raven) form one central roost. The total number of birds at the roost was typically 18 thousand individuals. The collective roost exists from the beginning of October till the end of March. The analysis of dynamics of the birds’ number during the existence of the collective showed a wide amplitude of fluctuation in the range of 1,000–5,000 individuals during autumn (10 times) and spring (5 times) migration. By the end of November migration ends, the number of birds has stabilized, and the location of the night roost becomes permanent. In winter the gathering is more stable and fluctuations in number lie within the limits of 500 individuals (8 times). The number of birds that roost collectively decreased from mid – March. In this article considerable attention is paid to processes of the birds’ dispersal from the roost site and gathering at the roost at night. The observations showed a high degree of dependence on day length and different intensity of these types of daily activity. During the analysis of the process of morning dispersal of birds from the collective roost, seasonal differences in the time of dispersal were found. In the winter months this period was significantly shorter than in the autumn and spring. The duration of dispersal of birds from the roost (28.4 ± 9 min; lim – 15–45 min) was reliably less than that of gathering at the roost (87.9 ± 14.8 min; lim – 30–115 min); the difference of averages is significant for the highest probability threshold of р ≥ 0.001 for the entire observation period. As a result of research on dispersal and gathering of birds at the roost site, the basic strategies of the birds’ behaviour were revealled. For morning dispersal of birds from the territory of the roost the strategy of “gathering with a pause” (16 registrations; 35.6%) is dominant. The strategy of “the damped wave” is sub dominant (14; 31.1%). The lowest percentage was taken up by the strategy of “three peaks” (1; 2.2%). For the evening gathering of birds at the roost, the strategy of “two peaks” is dominant. The lowest percentage was taken up by the strategy of “gathering with a pause” (2; 4.5%). The overall species diversity within a gathering and on the routes of birds’ flights reached 24 species. The undisputed dominant in numbers was the Rook, and the subdominan was the Jackdaw. Thus, corvids form the basis of the ornithological complex of the forest – park zone of Melitopol in the autumn and spring period.

This study analysed the effect of flowering time as influenced by photoperiod sensitivity genes on yield and yield stability in durum wheat. Twenty-three spring genotypes harbouring different allele combinations at Ppd-A1 and Ppd-B1 were grown in 15 field experiments at three sites at latitudes from 41&deg, to 19&deg, N (Spain, Mexico-North and Mexico-South). Low temperature and solar radiation before flowering and long day length during grain-filling characteristic for the Spanish site resulted in high grain number/m2 (GN) and yield (GY), while a moderate GN combined with high solar radiation during grain-filling at Mexico-North led to heavier grains. Allele combination GS100-Ppd-A1a/Ppd-B1a reduced the flowering time up to nine days when compared with Ppd-A1b/Ppd-B1a. Differences in flowering time caused by Ppd-A1/Ppd-B1 allele combinations did not affect yield. Combinations GS105-Ppd-A1a/Ppd-B1b and Ppd-A1b/Ppd-B1b resulted in the highest GN, linked to spikelets/spike, which was higher in GS105-Ppd-A1a/Ppd-B1b due to more grains/spikelet. Flowering time caused by Eps had a minor effect on GN, spikes/m2 and grains/spike, but late flowering resulted in reduced grain weight and GY. Allele combinations harbouring alleles conferring a similar photoperiod sensitivity response at Ppd-A1 and Ppd-B1 resulted in greater yield stability than combinations that carry alleles conferring a different response. Allele combination GS100-Ppd-A1a/Ppd-B1a was the most suitable in terms of yield and yield stability of durum wheat cultivated under irrigation within the studied latitudes.

Devising effective techniques for breeding and rearing rare non-migratory galaxiids is urgently required for conservation purposes where few animals exist in the wild for translocation or reintroduction. The development of such protocols is particularly pertinent in light of recent intense widespread bushfires and long-term drought in southeastern Australia, which have increased the likelihood of the need for captive maintenance to protect and recover remnant species. In this study, we promoted reproductive maturation via manipulation of day length and temperature, and produced viable offspring from two small, endemic freshwater galaxiids, Galaxias fuscus (Mack 1936) and Galaxias longifundus (Raadik 2014) using in vitro propagation techniques. Propagation trials resulted in 425 oocytes being stripped from four ripe G. fuscus females, and 1527 oocytes from three ripe G. longifundus females. Of these, 342 (80.5%) G. fuscus and 968 (63.4%) G. longifundus eggs hatched into larvae. Newly hatched G. fuscus and G. longifundus larvae were transparent, and 8.4–9.7 mm (mean 9.0 mm TL) and 7.1–8.9 mm (mean 8.3 mm TL) consecutively. Absorption of the yolk sac by G. fuscus larvae (1.5–2.0 mm diameter) was complete 6–7 days after hatching, and for G. longifundus (1.0–1.4 mm diameter) 12–13 days after hatching. One-month-old G. fuscus measured ~16 mm and two-month-old larvae ~22 mm, and one-month-old G. longifundus ~11 mm. Methods and techniques employed may aid broader galaxiid conservation efforts.

Understanding how populations adapt to constantly changing environments requires approaches drawn from integrative and evolutionary biology as well as population ecology. Timing of reproduction and migration reflect seasonal pulses in resources, are driven by day length, and are also responsive to environmental cues that change with climate. Researchers focusing on birds have discovered accelerated breeding, reductions in migration, and extensive variation in perception, transduction, and response to the environment. We consider situations in which individuals experience the same environment but differ in the timing of the annual cycle. Such scenarios provide exceptional opportunities to study mechanisms related to among-population differences in timing (allochrony) and distribution (sympatry–allopatry–heteropatry), which have the potential either to enhance or reduce population divergence and biodiversity.

We investigated whether a climatic change in temperature affected daily food intake in migrating male redheaded buntings. Groups of adult male birds (n = 18) were photoinduced into migratory phenotype under increasing spring daylengths (NDL); as the birds began to exhibit night restlessness, Zugunruhe, these were allocated into groups, either with ambient (NDL, variable daily temperature: maximum – 29–44 °C and minimum – 16–33 °C; for food intake (six birds) and activity recording, six birds) until 2 weeks after they concluded migration or with constant temperature (NDT, 22 ± 1 °C; for food intake (six birds)) conditions. As day length increased March onwards, daily food intake increased (hyperphagia) in NDL and NDT groups. However, hyperphagia was slower in NDT birds as compared to NDL birds, suggesting that altered ambient temperature affects daily food intake in migrating buntings. Another group of 12 birds were held under constant daylengths (12L:12D; EDT and constant temperature 22 ± 1 °C). Although ...

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and...

The shortening of day lengths is known to advance the late-summer and autumn events of the annual cycle preceding migration in late-hatched individuals in order to synchronize the individual cycles of birds that hatched on different dates. However, little is known about how day length influences behavior during autumn migration. Here, we tested the locomotory activity of first-year migrant Long-tailed Tits (Aegithalos c. caudatus) from northwestern Russia under two different photoperiodic conditions during the autumn migration period. The birds were taken into the experiment after they started their migration in the wild, and assigned to either the control (natural photoperiod) or the experimental group (photoperiod shifted 1 mo ahead to simulate shorter days). In the beginning of the experiment, locomotory activity was the same in both groups. After 3 weeks, however, individuals exposed to the light regime simulating a delay on the migration route (i.e. shorter days) showed higher levels of loco...

The effects of temperature and food availability on social bonds and group formation are poorly understood. Because seasonal transitions in female social behavior facilitate the assembly of winter groups in meadow voles, we explored the role of same-sex female associations in winter sociality. To examine the effects of winter typical environmental conditions on same-sex female affiliative behavior, paired female meadow voles were housed in varying combinations of day length, temperature, and food availability for 7 weeks and then tested for social preference. In short days (SDs), lower ambient temperature increased huddling with unfamiliar females without interfering with existing social bonds, whereas lower temperature disrupted the retention of bonds in long days (LDs). Mild food restriction with no discernible effects on body mass enhanced affiliative behavior in SDs, but not LDs. A second experiment examined the effects of sex and day length on the propensity to aggregate with unfamiliar same-sex voles. Compared to LD females and SD males, SD females spent more time in group huddles with unfamiliar voles and displayed no social preference. These outcomes indicate that winter-like conditions enhance affiliative behavior between females and that pre-existing social bonds do not preclude integration into new winter social groups. The adaptive value of these behaviors is discussed.

The effects of day length on preimaginal development and reproductive maturation of females of laboratory strains which originated from two native: Irkutsk (Siberia, Russia) and Daegu (South Korea) and two invasive: Sochi (Caucasus, Russia) and Pardubice (Czechia) populations of Harmonia axyridis were investigated under the laboratory conditions. In all the 4 strains, the acceleration of development caused by the short day (all other conditions being equal) was relatively stronger in those larvae that later, at the adult stage, delayed reproductive maturation. This correlation can be considered as an indirect proof that both reactions are based on the common physiological mechanism. However, comparison of the parameters of photoperiodic responses showed that although the photoperiodic effect on reproductive maturation in individuals from Sochi and Pardubice invasive populations was relatively weak, the effect of day length on the rate of their preimaginal development was even somewhat stronger than that of individuals from Irkutsk and Daegu native populations. This uncorrelated interpopulation variation of the quantitative and qualitative photoperiodic responses suggests that in spite of the common physiological mechanism, the responses influencing preimaginal development and reproductive maturation of H. axyridis are to a certain extent independent and thus the evolution of their parameters (in particular, adaptation to new climate conditions) occurs independently.

Life on Earth has evolved in a periodic world, which in most environments cycles predictably between conditions that are favourable or unfavourable for an organism. Organisms use favourable seasons to reproduce and grow, and withdraw during unfavourable seasons. To deal with the predictable changes in their environments, all taxonomic groups have evolved genetically programmed timing mechanisms. These govern seasonal cycles in physiology and behaviour that optimise survival and reproductive success, and have been formally described as circannual rhythms. Experimentally, under conditions of constant day length and temperature, circannual rhythms of many species continue to be expressed, even throughout the life cycle, illustrating the fundamental endogenous control. Under natural conditions, they are usually entrained by seasonal time cues, notably photoperiod, to synchronise the biology to environmental periodicity. Here we review long-term timekeeping strategies from classical vertebrate models to invertebrate and unicell life histories. These circannual rhythms enable organisms to anticipate Earth’s periodicity.

Measuring day length confers a strong fitness improvement to photosynthetic organisms as it allows them to anticipate light phases and take the best decisions preceding diurnal transitions. In close association with signals from the circadian clock and the photoreceptors, photoperiodic sensing constitutes also a precise way to determine the passing of the seasons and to take annual decisions such as the best time to flower or the beginning of dormancy. Photoperiodic sensing in photosynthetic organisms is ancient and two major stages in its evolution could be identified, the cyanobacterial time sensing and the evolutionary tool kit that arose in green algae and developed into the photoperiodic system of modern plants. The most recent discoveries about the evolution of the perception of light, measurement of day length and relationship with the circadian clock along the evolution of the eukaryotic green lineage will be discussed in this review.

This study provides the first direct observations that photoperiod controls the initiation of downstream movement in Atlantic salmon Salmo salar smolts. Under simulated natural day length (LDN) conditions and seasonal increases in temperature, smolts increased their downstream movements five-fold for a period of 1 month in late spring. Under the same conditions, parr did not show changes in downstream movement behaviour. When given a shortened day length (10L:14D) beginning in late winter, smolts did not increase the number of downstream movements. An early increase in day length (16L:8D) in late winter resulted in earlier initiation and termination of downstream movements compared to the LDN group. Physiological status and behaviour were related but not completely coincident: gill Na(+) /K(+) -ATPase activity increased in all treatments and thyroid hormone was elevated prior to movement in 16L:8D treatment. The most parsimonious model describing downstream movement of smolts included synergistic effects of photoperiod treatment and temperature, indicating that peak movements occurred at colder temperatures in the 16L:8D treatment than in LDN, and temperature did not influence movement of smolts in the 10L:14D treatment. The complicated interactions of photoperiod and temperature are not surprising since many organisms have evolved to rely on correlations among environmental cues and windows of opportunity to time behaviours associated with life-history transitions. These complicated interactions, however, have serious implications for phenological adjustments and persistence of S. salar populations in response to climate change.

In seasonally breeding birds annual changes occur in hormone production by the hypothalamic-pituitary-gonadal (HPG) axis as individuals transition between breeding and non-breeding condition. Typically, some external environmental cue induces the observed changes; changes in day length, corresponding to change of seasons, are a strong cue for HPG axis activity in many species. Some species use cues other than day length as their primary initiator of breeding, and a number of light-sensitive species incorporate other cues to initiate breeding. Northern Cardinals (Cardinalis cardinalis) exhibit individual variation in when breeding begins and circulating testosterone is present throughout the year. Chemical tests of HPG axis responsiveness indicate that many individuals have an activated HPG axis as early as December. Here we use GnRH injections to assess whether individuals with active HPG axes prior to the winter solstice and increasing day lengths, may be influenced to initiate breeding by low t...

The distribution limits of the beet webworm, Loxostege sticticalis L., with its sustainable development in one, two, three, or four successive generations per season in the former USSR territory were mapped for the first time using routine GIS procedures. The expected number of generations was determined based on the sum of daydegrees (above a threshold of 12°C), critical day length value (14 h), and Selyaninov’s hydrothermal index (> 0.3). The compiled map was in good agreement with that prepared for China (Luo Li-zhi and Li Guang-bo, 1993).

We gratefully acknowledge the financial support provided by the British Ornithologists’ Union and the African Bird Club. During incubation, tropical passerines have been shown to have lower levels of nest attentiveness than their counterparts at north temperate latitudes, spending a higher percentage of daylight time off the nest. This difference has been interpreted as evidence of parental restraint; tropical birds allocate more time to daily self-maintenance, perhaps preserving their higher annual survival rates and future breeding potential. But such comparisons are susceptible to the confounding effects of day length variation, because a given amount of time spent off the nest will account for a greater percentage of daylight time near to the equator than at high latitudes during spring and summer. Based on a pattern of increasing day length between 0° and 70°N, we show that the impact of this bias is likely to be small where sites are separated by less than 30°–40° of latitude, but should increase substantially both with latitudinal span and distance from the equator. To illustrate this effect, we compared nest attentiveness in two congeners breeding at 1°S and 52°N. During incubation, Stripe-breasted Tits Parus fasciiventer in Uganda had a shorter working day (time from emerging to retiring) than north temperate Great Tits P. major, and spent a higher percentage of daylight time off the nest (32 %) than Great Tits in the UK (24 %). However, this difference was almost wholly explained by the latitudinal difference in day length; the amount of time spent off the nest differed by just 10 min day−1 (

This study investigated bud burst and onset and cessation of radial growth (i.e., secondary xylem cell production by cambium) along an altitudinal gradient (1,600–2,800 m a.s.l.) in central Japan, to examine whether timing of the three phenological events are controlled by thermal conditions alone, irrespective of altitude. Measurement was done at biweekly intervals during 3 years (2006–2008) for four subalpine tree species at their upper and lower distribution limits, except for bud burst in 2006. Although bud burst and onset of radial growth were later at higher altitudes in the combined data of the four species, cessation of radial growth occurred in mid-August, irrespective of altitude. Coefficients of variation of timing of the phenological events decreased in the order bud burst, onset of radial growth, and cessation of radial growth in combined data of the four species. Growing degree days (GDD) for bud burst did not differ greatly along the altitudinal gradient for each species. However, GDD for the onset of radial growth was lower at higher altitude. This study suggests that the effects of thermal conditions on the phenological events along the altitudinal gradient might decrease in the order bud burst, onset of radial growth and cessation of radial growth. Probably not only temperature, but also other factors such as day length, may affect onset and cessation of radial growth. However, further research is necessary to examine the altitudinal differences in timing of the phenological events more accurately, by measurements at shorter time intervals than the biweekly intervals of this study.

To clarify temporal variation of in situ egg production of the copepods, Acartia japonica Mori, 1940, in Sagami Bay, central Japan, the species’ abundance, egg morphology and hatching patterns were studied during 2015. Adults of A. japonica were observed in the water column from June to October. Results showed that adults reared in the laboratory produced three types of eggs: subitaneous, delayed-hatching and diapause. All egg types had a surface covered with short spines; diapause eggs had a thicker chorion than subitaneous eggs. During the early period of the species occurrence in the bay, most females produced only subitaneous eggs, which hatched within 72 h. From the end of September, a large proportion of females began to produce diapause eggs. Linear regression analysis showed that the ratio of diapause eggs was negatively correlated with day length and water temperature (P

We collected data from 10 caves (3 sites) in the North and Middle Andaman Islands to determine the spatiotemporal changes in the roosting pattern of the Andaman populations of Edible-nest Swiftlet (Aerodramus fuciphagus inexpectatus). This echolocating diurnal aerial forager showed temporal variation in its round-the-clock entry and exit patterns. With spatiotemporal variations (site-wise, cave-wise, hourly, and monthly), more than 98% of birds returned daily to the roosting caves between 1700 h and 2000 h. However, their daily departure time (between 0400 h and 0700 h) did not vary spatially (site-wise and cave-wise). The movements of birds at the cave openings were higher during the nestling period in April and May. The daily roosting period inside the caves (mean 525.20 min; SD 82.98) also showed spatiotemporal variation. Day length affected movement of the birds before and after sunset and sunrise. We conclude that roosting movement of the Andaman Edible-nest Swiftlet varied spatiotemporally in the Andaman Islands. This first detailed description of such variation in the roosting patterns of the species will stimulate further exploration of the various biological and environmental factors affecting movements of this cave-dwelling endemic.

Field experiments conducted in the environs of St. Petersburg (Russia) with a local population of Calliphora vicina showed that induction of larval diapause under natural conditions was significantly dependent on day lengths and temperature. The maternal photoperiodic response had a distinct threshold: the first diapausing larvae hatched from the eggs laid in the middle of August when the day length was 16 h; at shorter photoperiods, the fraction of diapausing larvae depended only on temperature. At the mean temperature of 16°C, larval diapause was rarely recorded; at 12–13°C, about 50% of the larvae entered diapause; at 7–9°C, nearly all the larvae entered diapause. These results of the field experiments agree well with the parameters of photoperiodic and thermal responses studied in the laboratory at constant temperatures and photoperiods.

Maternal and grand-maternal photoperiodic responses of Trichogramma buesi, T. embryophagum, T. evanescens, T. piceum, T. principium, and T. telengai were investigated in laboratory conditions. During the experiment, grand-maternal and maternal generations developed at 20°C and one of the 4 photoperiodic regimes: L : D = 12 : 12, 14 : 10, 16 : 8, and 18 : 6 (in total, 16 combinations) while the progeny developed at L : D = 12 : 12 and one of the 3 thermal regimes: 13, 14, and 15°C. The proportion of diapausing individuals in the progeny of all the studied species was significantly dependent on the direct influence of temperature and on the maternal photoperiodic response. The influence of the photoperiodic conditions during development of the grand- maternal generation was statistically significant in 5 of the 6 studied species, being relatively weak in T. embryophagum and T. telengai, whose geographical ranges extend up to north-western regions of Europe (possibly, these wasps enter diapause so early that the grand-mothers of the diapausing generation develop under long day conditions). Comparative analysis showed that the thresholds of the maternal and grand-maternal photoperiodic responses coincided or almost coincided. The grand-maternal effect was stronger in the progeny of maternal females which developed under short day conditions than in those that developed under long day condi- tions. This pattern of interaction probably synchronizes the life cycle with seasonal changes because diapause is induced under decreasing day length and thus mothers of diapausing individuals develop at shorter daylength than do grand-mothers. We conclude that the grand-maternal and the maternal effects on Trichogramma progeny diapause are based on one and the same photoperiodic response. In nature, the grand-maternal effect increases the proportion of diapausing individuals in the progeny of females which have developed under short day conditions during two generations, thus achieving a "cumulative" photoperiodic effect.

Summary The present study investigated the spawning behaviour of the spiny eel, Macrognathus pancalus, and its relationship with the environment (photoperiod and temperature). The results show that M. pancalus breeds during February to September with peak spawning during February/March and July/August, indicating two main breeding periods. Initiation of breeding occurs during increasing day lengths in early spring (February/March), and regression during decreasing day lengths in autumn (September/October). The breeding status confirmed by gonadosomatic index (GSI) and ovarian histology showed six stages of ovarian maturation (viz. stage I: chromatin nucleaolar; II: perinucleolar; III: cortical alveolar; IV: vitellogenesis; V: ripe; and VI: partially spent), with predominance of one or more stages at a particular time of the year. Males also followed a similar seasonal pattern in gonadal maturation as reflected by their GSI. Results show that M. pancalus is a seasonal breeder with bimodal spawning activity. The breeding pattern suggests an influence of prevailing day length conditions at this latitude.

Day length regulates the development of seasonal phenotypes linked with both the spring migration (e.g., premigratory body fattening and intense nighttime restlessness, called Zugunruhe, in captive birds) and reproduction (e.g., gonadal growth and maturation). The apparent overlap in these photoinduced seasonal phenotypes could be taken to suggest that they are causally linked. The present study investigates this, using the night-migratory blackheaded bunting (Emberiza melanocephala). We continuously monitored activity of male buntings exposed for 19 weeks to short (8 h light : 16 h darkness; 8L : 16D) and long (16L : 8D) photoperiods. Long, but not short, days induced the spring migratory phenotype. Another experiment investigated the role of testes in spring migration by comparing the development of Zugunruhe between intact and castrated buntings held on natural day lengths, at Meerut (India, 29°01′N, 77°45′E) during the period from March to October, thus covering the times of both the spring and autumn migrations. Testes were not involved in induction of the migratory phenotype but probably influenced the end of the migratory season, since castrates delayed the termination of the Zugunruhe.

Sit-and-wait ambushing and active hunting are two strategies used by predators to capture prey. In snakes, hunting strategy is conserved phylogenetically; most species employ only one strategy. Active hunters encounter and capture more prey but invest more energy in hunting and have higher risks of being predated. This trade-off is important to small predators. The small Cerastes vipera employs both modes of hunting, which is unlike most viperids which use only sit-and wait ambushing. This species hibernates in October and emerges in April. Energy intake should be high prior to hibernation to overcome the non-feeding hibernation period and for reproduction on their emergence. We predicted that more individuals would hunt actively towards hibernation and an abiotic factor would trigger this response. Furthermore, since more energy is required for active hunting, we predicted that snakes in good body condition would use active hunting to a greater extent than snakes in poor body condition. To test our predictions, we tracked free-living snakes year round and determined their hunting strategy, estimated their body condition index (BCI), and calculated circannual parameters of day length as environmental cues known to affect animal behaviour. Two novel findings emerged in this study, namely, hunting strategy was affected significantly by 1) the circannual change in day length and 2) by BCI. The proportion of active hunters increased from 5% in April to over 30% in October and BCI of active foragers was higher than that of sit-and-wait foragers and, therefore, our predictions were supported. The entrainment between the proportion of active hunting and the abiotic factor is indicative of an adaptive function for choosing a hunting strategy. A trend was evident among life stages. When all life stages were present (September–October), the proportion of active foragers increased with age: 0.0% among neonates, 18.2% among juveniles and 31.4% among adults. We concluded that vulnerable small neonates used sit-and-wait ambush not only as a hunting strategy but also as a hiding technique.

Made available in DSpace on 2018-12-11T17:01:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-08-01 Key message: Cambial dormancy in a tropical evergreen species is long lasting, and the initiation of cambial activity is related to day length. Abstract: Studies on cambial activity allow us to understand the growth dynamics of plants. In this study, we investigate cambial activity and the conducting phloem in a population of an evergreen shrubby species from a semi-deciduous tropical forest with distinct wet and dry seasons. Stem samples from Cordiera concolor were collected bimonthly in 2010 and prepared according to the standard methods for plant anatomy. The relationship between cambial activity and climate factors as well as phenology was investigated using Spearman’s correlation. The cambium is dormant during the rainy season and dormancy lasted up to 9 months. Cambial activity was positively related to day length, and although it occurred in the rainy season, the period of its onset and termination was not concurrent with the beginning and end of the rainy season. The conducting phloem corresponded most to the non-collapsed phloem and was present year-round, ranging in width (in transverse section) from 62 µm in the rainy season to 112 µm in the dry season. Together, these results illustrate that cambial activity in an evergreen species of a seasonal tropical forest is seasonal with long-lasting cambial dormancy, and that at least some conducting phloem is present year-round. Programa de Pós-Graduação em Ciências Biológicas (Botânica) Instituto de Biociências de Botucatu Univ Estadual Paulista (UNESP) Dep. Ciência Florestal Faculdade de Ciências Agronômicas de Botucatu Univ Estadual Paulista (UNESP) Programa de Pós-Graduação em Ciências Biológicas (Botânica) Instituto de Biociências de Botucatu Univ Estadual Paulista (UNESP) Dep. Ciência Florestal Faculdade de Ciências Agronômicas de Botucatu Univ Estadual Paulista (UNESP)

Sexual segregation is common in ungulates. We show, in a high latitude population of feral goats where behavioural synchrony and fission rates have been shown to be the best explanation for segregation, that it is differences explicitly in the feeding time requirements of the two sexes (but not those for other activities) that best explains the variations in monthly frequencies of segregation. However, this effect is less marked during winter months when short day length forces the time budgets of the two sexes to converge. We argue that the various explanations for segregation can best be interpreted as separate factors in a multivariate model in which species- and habitat-specific weightings influence the relative importance of these variables, and thus the likelihood that segregation will occur. © 2008 The Authors.

Common buckwheat (Fagopyrum esculentum Moench.) has been cultivated in Eastern Europe for a very long time. The territory may be considered as a secondary center of buckwheat genetic diversity. In comparison with varieties from East Asia, which are very late when grown in conditions of long summer days in northern regions, the European local varieties do not sufficiently change the length of vegetation period in different day length conditions. Peculiarities of adaptation of buckwheat to the huge area of Eastern Europe are described in this chapter; the main requirement for such adaptation is matching the vegetation period of the population with the frost-free period in the region. The morphological criteria for selection on the specific vegetation period are described. The main buckwheat breeding directions are reviewed.

Descriptions of lek-breeding in White-bearded Manakins (Manacus manacus) first appeared 55 years ago from studies conducted in tropical Trinidad. No published studies on lek activity, however, exist from subtropical areas of the Neotropics. Herein, annual lek phenology of M. manacus in a subtropical region was analysed and compared with studies conducted in Trinidad. Day-long observations were conducted in nine male territories from three leks. Permanence of lekking males in their territories was positively correlated with day length. When males are more active in the subtropical region, males from Trinidad are less active and vice versa. Additional new information about this manakin's lek activity was disclosed: residents stayed in their courts for up to 7% of the day length, the frequency and duration of display bouts of residents varied throughout the year whereas those of juveniles did not, and females made more visits to courts of residents who displayed for longer bouts.

The plasma metabolites triglycerides (TRIG) and b-hydroxybutyrate (BUTY) are used as indices of nutritional condition in migrating birds during refuelling and can provide a measure of relative fattening rates in individual birds. Because non-migratory birds wintering at northern latitudes also fatten on a daily basis to support their overnight fast, blood metabolites could provide a useful tool to measure individual performance in energy acquisition. However, daily patterns of metabolite change may differ between species and could be affected by thermoregulatory requirements. We studied daily variation in TRIG and BUTY over a complete winter in Black-capped Chickadees to determine the pattern of daily and seasonal change in these markers. We also assessed how short-term variation (up to 7 days) in weather parameters that influence heat exchange may affect TRIG and BUTY levels. In contrast to a linear gain of body mass, TRIG increased non-linearly during the day, with a rapid increase in the morning that levelled off in the afternoon, whereas BUTY did not change significantly. Metabolites varied with sampling time and the seasonal change in day length, suggesting higher fat catabolism and fattening rates in mid-winter. TRIG and BUTY also differed between capture sites, possibly due to differences in shelter quality. Weather variation did not affect TRIG levels and had a significant but marginal effect on BUTY, explaining at best 3% of the variation. Our results suggest that these markers can be used as indicators of energy turnover in resident wintering passerines.