Seasonal Alternation Research Articles

Engineering the crack path in lattice cellular materials through bio-inspired micro-structural alterations

A computational study on the fracture behaviour of bio-inspired finite-size lattice configurations is performed in this work. The study draws inspiration from recent investigations aimed at increasing the fracture energy of some materials through small modifications of their microstructure. The main question here is whether it is possible, to some extent, to engineer the crack path in metallic cellular materials through such small micro-structural modifications and how to quantify the effect of alternative strategies. Nature provides several examples of strategies used to delay or arrest damage and crack propagation. One striking example is given by the micro-architecture of several kinds of wood, in which the crack propagation through a lignin cellular matrix is affected by density variations typical of the seasonal alternation between early-wood and late-wood and by the presence of sap channels. In this study, the effects on crack propagations induced by micro-structure alterations inspired by density variations and sap channels in wood are computationally investigated and some figures of merit are defined to assess the effect on the energy absorbed by alternative solutions. In an age in which tight control of the microarchitecture can be achieved, e.g. through high-resolution 3D printing, it is of interest to investigate whether, starting from a baseline cellular architecture, it is possible to achieve superior material performance by smart modifications of the microarchitecture.

Maastrichtian to early Paleocene sea level changes and climatic evolution on the southeastern Tethys margin

Abstract An integrative multi proxy approach based on lithology, microfacies, bulk rock composition, total organic carbon (TOC), and δ13Ccarb was used to estimate southeastern Tethys sea level fluctuations during the deposition of the Maastrichtian-Danian oil shales in Jordan. Clay mineral assemblages were used as proxies to determine climatic variation induced sediment supply during the Cretaceous/Paleogene boundary (K/Pg) interval. The results from two cores (OS-02, Jafr Basin, southeast Jordan; OS-28 Azraq-Hamza Basin, central-east Jordan) reveal four major intervals of distinctive bulk rock composition reflecting sea level changes. Interval I (earliest Maastrichtian) with a low sea level and the formation of dolomites and a high detrital quartz input predates the oil shales. Intervals II and III in core OS-02 and interval II in core OS-28 represent the highest relative sea level following the Early Maastrichtian sea level rise on the Arabian Platform. Intervals III (core OS-02) and II (core OS-28) coincide with the highest organic matter deposition. Interval IV (core OS-02) and intervals III and IV (core OS-28) relate to the sea level regression-transgression cycle in the latest Maastrichtian through Danian and are marked by a large drop in the TOC content. Increased terrestrial influx during sea level lows is evident from two peaks/intervals of major negative δ13Ccarb values in core OS-28. Based on clay mineralogy it can be differentiated between warm/humid, warm/cool seasonally alternating, and cool/arid climates. When bulk rock composition is used as a sea level proxy, clay mineral assemblages from both cores reveal the dominance of warm and humid climate or, alternatively, warm/cool seasonal alternations during high sea levels (II and III core OS-02; II and IV core OS-28), while periods of arid and cool climate correspond to lower sea levels. The sea level changes and climatic variations deduced from the Jordanian oil shale successions are in agreement with the long term variations from the Egyptian Western Desert sections (southeastern Tethys), and the Tunisian El-Kef section (southweastern Tethys). Moreover, the sea level changes identified relate to the regional changes on the Arabian platform during the Maastrichtian-Danian.

Antimony speciation at the sediment-water interface of the Poyang Lake: response to seasonal variation

In order to identify the effects of seasonal variation on the migration and transformation of antimony species at the sediment-water interface of the Poyang Lake, the largest fresh lake in China, a simulation study was carried out in the laboratory. Antimony species including antimonite Sb(III), antimonate Sb(V) and the fraction of organic forms (Sb-org) in overlying water at different temperatures were regularly measured during the simulation period. Different bound antimony forms in sediments were also determined along with the different antimony species in porewaters after the simulation terminated. The results indicated that temperature change during seasonal alternation plays an important role in the migration and transformation behavior of antimony at the sediment-water interface of the Poyang Lake. Antimony species both in porewaters and overlying water were sensitive to the variation of temperature, especially the Sb-org species. Antimony migrates from porewaters to the overlying water when the temperature decreases, and meanwhile the equilibrium between Sb(III) and Sb(V) in porewaters shifts toward Sb(V) when the temperature increases during seasonal alternation. Although temperature had less influence on the antimony species in sediments than in porewaters or in the overlying water, the average content of each antimony species in sediments increased with the decrease of temperature, suggesting that the decrease of temperature causes enrichment of antimony in the sediment.

Coastal wetlands as markers of transgression in proximal extensional systems (Berriasian, W Cameros Basin, Spain)

The early stages of intraplate extensional systems commonly are recorded by deposition of continental sediments. In this context, given appropriate tectonics and eustasy, transgressions can be well recorded in the areas of the basins located close to the sea, but they may be difficult to recognize in the innermost landwards areas of the system. This situation occurs in the innermost Upper Jurassic-Early Cretaceous Cameros Basin, part of the Iberian Extensional System (N. Spain), where a Berriasian transgression is recorded. The Berriasian succession in this area consists of siliciclastic deposits (sandstone and mudstone) of the Salcedal Formation and of carbonate and mixed carbonate-fine siliciclastic deposits (limestone and marl) of the San Marcos Formation. The sedimentological analysis of this depositional succession indicates that a Berriasian carbonate coastal wetland system occupied that sector of the Cameros Basin during deposition of the San Marcos Formation. This carbonate coastal wetland system consisted of shallow and quiet water bodies including some with marine influence others with no to very little marine influence, and palustrine areas. A semiarid climate characterized by the seasonal alternation of short wet and long dry periods caused water bodies of the system to undergo episodic desiccation and subaerial exposure. Moreover, this complex mosaic of sub-environments was connected laterally with a distal zone of a distributive fluvial system that was rimmed by siliciclastic tidal flats during phases of greater marine influence. The paleogeographic arrangement of this coastal wetland depositional system indicates that the marine influence came from the Basque-Cantabrian Basin to the north. During the period of Berriasian maximum marine influence, accommodation linked to the eustatic rise added to accommodation generated by tectonic subsidence from the extensional reactivation of late Variscan strike-slip faults. All these factors favored marine incursion into the west Cameros Basin from the Basque-Cantabrian Basin to the north. The example of the Berriasian transgression recorded in the W Cameros Basin by establishment of coastal wetland systems matches the interpretations of previous studies in neighboring areas. In those areas, complex coastal systems record transgressions in the innermost parts of the intraplate extensional basins of the Iberian Plate. This observation suggests that this paleogeographic and sedimentological arrangement may be common in the innermost parts of intraplate extensional basins during transgressive episodes throughout the geological record.

Variations of Bacterial Community Composition and Functions in an Estuary Reservoir during Spring and Summer Alternation.

In this study, we focused on the dynamics of bacterial community composition in a large reservoir in the Yangtze estuary during spring and summer seasons, especially the variations of functional mechanisms of microbial community during the seasonal alternation between spring and summer. Both 16S rRNA gene sequencing and shotgun metagenomic sequencing technology were used for these purposes. The results indicated that obvious variations of bacterial community structures were found at different sites. Particle-associated bacterial taxa exhibited higher abundance at the inlet site, which was closer to the Yangtze River with a high level of turbidity. In other sites, Synechococcus, as the most dominant cyanobacterial species, revealed high abundance driven by increased temperature. Moreover, some heterotrophic bacterial taxa revealed high abundance following the increased Synechococcus in summer, which indicated potential correlations about carbon source utilization between these microorganisms. In addition, the shotgun metagenomic data indicated during the period of seasonal alternation between spring and summer, the carbohydrate transport and metabolism, energy production and conversion, translation/ribosomal biogenesis, and cell wall/membrane/envelope biogenesis were significantly enhanced at the exit site. However, the course of cell cycle control/division was more active at the internal site.

Pre-Training Hydration Status of Well- Trained Soccer Players in Moderate Temperature Autumn and Cool Winter

Background. Pre-training hydration status is considered a factor influencing efficacy of training. Research literature does not contain data regarding the potential impact of natural alternation of seasons on pre-training hydration status in athletes. The purpose of this study was to assess and compare pre-training hydration status in well-trained male soccer (football) players in moderate temperate autumn and cold winter.Methods. Research participants were 57 male soccer players from two Latvian First League teams, who were studied prior to their ordinary training session. Participants provided a midstream urine sample for analysis of urine specific gravity (USG), and their body mass (kg), body fat percentage and total body water percentage were measured. Results. Pre-training hydration status did not differ in moderate temperature autumn (mean USG 1.020 ± 0.010; mean total body water 64.2 ± 2.9%) in cold winter (mean USG 1.020 ± 0.008; mean total body water 64.8 ± 2.7%; for both parameters p > .05). Prevalence of hypohydration and serious hypohydration (defined as USG 1.021 – 1.030 and USG > 1.030, respectively) was similar in moderate temperate autumn (47.4%) and cold winter (60%), (χ 2 = 1.50; p > .05). Significant correlation between the within-subject USG values measured in moderate temperate and cold environment was observed (r = .60, p = .009). Conclusion. In well-trained soccer players pre-training hydration status does not differ in moderate temperature autumn and cold winter. Individual-related factors such as nutritional behaviour (including pattern of voluntary fluid intake) may have stronger impact on hydration status than environment-related factors like natural alternation of seasons.Keywords: hydration status, football, environmental temperature, autumn, winter.

An Analysis of Tess of the d’Urbervilles in the Light of Eco-feminism

Thomas Hardy is a famous English writer of critical realism in the late 19th century. Tess of the d’Urbervilles is one of his most influential masterpiece, which Hardy reveals his affinity to Eco-feminism in his views toward nature and women. The novel depicts a country woman, who is unsophisticated, kind-hearted and with natural image, however ends her life in tragedy. Throughout Tess’s whole life in every aspect, the author reveals that the capitalism is permeating into rural areas, which implies his sympathy for those women who are under great oppression but cultivated consciousness of Eco-feminism ahead of time. In order to stress the harmonious relationship between women and nature, he concentrates much on beautiful natural scenery in the area of Wessex. In the characterization, Tess behaves as the daughter of nature, who has a mysterious and intimate connection to nature: her fate even complies with the alternation of seasons. Industrialization and patriarchy has become the root of Tess’s death. The Eco-feminist interpretation of Tess of the d’Urbervilles aims to call on a profound retrospection on the relationship between nature, women and men. The awareness of environmental protection and of rebuilding the mutual harmony between human and nature, men and women, are also hoped to be provoked.

Somatic Polymorphism Variation in <i>Crotalaria retusa</i> L. Seeds

The article describes the somatic polymorphism in Crotalaria retusa L. seeds. Each individual may produce yellow dormant seeds, brown quiescent seeds and unviable dark brown ones. Therefore, regarding physiology it is a dimorphism. We show that autogamy reduces dimorphism, favoring the formation of dormant seeds. However, the significant variation in dimorphism is seasonal as consequence of increased viability of dormant seeds under drier weather conditions. The variation is a phenotypic response to changes of humidity in the environment during plant reproduction, a mechanism inducing the prevalence of dormant seeds in the dry season and quiescent seeds during the rainy season. The seasonal alternation between dormancy and quiescence in seasonally dry environments has an apparent adaptive value. The chromatic polymorphism increases on the more humid coast and during the rainy season, due to increased mortality of dormant seeds under wetter weather conditions. Unviable seeds accumulate oxidized phenols in their seed coat that possibly act as induced chemical defenses. Its proportion increases with humidity, accentuating polymorphism, also in response to the increase in the predation rate by larvae of U. ornatrix during the rainy season.

Soil-atmosphere Interaction as Triggering Factors of Openings between Embankment and Pavement

The analysis of openings between embankment and pavement due to uneven deformations of the highway embankment is incapable of accurate prediction when the pattern of seasonal weather variation is considered. This realization was used for elaborate openings analyses which include infiltration and evapotranspiration of the embankment soils to better predict atmosphere-induced openings between embankment and pavement at Nairobi where the longitudinal cracks of the pavement structure occurred during the period of the season alternation. The empirical equations were used to estimate evapotranspiration and the soil–water characteristic curve was established for the embankment soils. The consolidation theory and the moisture swelling model were then used to estimate performances of the highway embankment under atmospheric influence. A field test was conducted to verify the simulated moisture change in soil and soil movement, and small difference between simulated and measured values was found. The results showed that openings between embankment and pavement would occur when the highway embankment had undergone uneven deformations due to the rainfall and evapotranspiration, there were small openings during the dry season, but the maximum openings reached 10.2 mm and 25.5 mm during the first rainy season and the most intense rainy season, respectively.

Constraints on the dispersal of Mt. Vulture pyroclastic products: implications to mid-Pleistocene climate conditions in the foredeep domain of southern Italy

Mt. Vulture volcano is located on the thrust front of the southern Apennines. Its mid-Pleistocene products are spread southeastward in the adjacent Bradano foredeep basin. The stratigraphic record of the volcano within the Quaternary sedimentary successions helps to better understand the paleo-environmental setting of the foredeep. Volcaniclastic deposits cropping out close to the edifice, tephra levels and associated paleosols recovered from the southernmost sector of the foredeep are of key importance in reconstructing the Pleistocene morpho-climatic conditions in which they formed, using a multiproxy approach. Geomorphological observations and stratigraphic sampling come from the Venosa lacustrine-alluvial basin and from the areas of Irsina and Pomarico villages, where pumice fall levels and related paleosols are present at the top of the lower-middle Pleistocene sedimentary succession. Geochemical and mineralogical analyses of paleosols and pyroclastic rocks have indicated that the Pomarico pumices, reworked and deposited in an alluvial environment, could be likely correlated to the Fara d'Olivo ignimbrites (39Ar/40Ar age < 687 ± 8 ka) present in the basal unit of the Mt. Vulture volcanic succession. The presence of a 7A halloysite phase in the paleosols from two different sites suggests that the Pleistocene weathering likely developed in a dry-humid climate with an alternation of rainy seasons and dry periods.

How competitive is drought deciduousness in tropical forests? A combined eco-hydrological and eco-evolutionary approach

Drought-deciduous and evergreen species are both common in tropical forests, where there is the need to cope with water shortages during periodic dry spells and over the course of the dry season. Which phenological strategy is favored depends on the long-term balance of carbon costs and gains that leaf phenology imposes as a result of the alternation of wet and dry seasons and the unpredictability of rainfall events. This study integrates a stochastic eco-hydrological framework with key plant economy traits to derive the long-term average annual net carbon gain of trees exhibiting different phenological strategies in tropical forests. The average net carbon gain is used as a measure of fitness to assess which phenological strategies are more productive and more evolutionarily stable (i.e. not prone to invasion by species with a different strategy). The evergreen strategy results in a higher net carbon gain and more evolutionarily stable communities with increasing wet season lengths. Reductions in the length of the wet season or the total rainfall, as predicted under climate change scenarios, should promote a shift towards more drought-deciduous communities, with ensuing implications for ecosystem functioning.

Temperature seasonality control on modern halite layers in the Dead Sea: In situ observations

Layered halite sequences are found in deep basins throughout the geological record. However, analogs for such sequences are commonly studied in shallow environments. Here, we studied active precipitation of halite layers from the only modern analog for deep, halite-precipitating basins, the hypersaline Dead Sea. In situ observations in the Dead Sea link seasonal thermohaline stratification, halite saturation, and the characteristics of the actively forming halite layers. The spatiotemporal evolution of halite precipitation in the Dead Sea was characterized by means of monthly observations of (1) lake thermohaline stratification (temperature, salinity, and density), (2) degree of halite saturation, and (3) textural evolution of the active halite deposits. We present the observed relationships between the textural characteristics of layered halite deposits (i.e., grain size, consolidation, and roughness) and the degree of saturation, which in turn reflects the limnology and hydroclimatology. The lake floor is divided into two principal environments: a deep, hypolimnetic lake floor and a shallow, epilimnetic lake floor. In the deeper hypolimnetic lake floor, halite continuously precipitates with seasonal variations: (1) During summer, consolidated coarse halite crystals form rough surfaces under slight supersaturation. (2) During winter, unconsolidated, fine halite crystals form smooth lake floor deposits under high supersaturation. These observations support interpretations of the seasonal alternation of halite crystallization mechanisms. The shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations, and by intensive summer dissolution of part of the previous year’s halite deposit, which results in thin sequences with annual unconformities. This emphasizes the control of temperature seasonality on the characteristics of the precipitated halite layers. In addition, precipitation of halite on the hypolimnetic floor, at the expense of the dissolution of the epilimnetic floor, results in lateral focusing and thickening of halite deposits in the deeper part of the basin and thinning of the deposits in shallow marginal basins.

Seasonal Pattern In the High-Elevation Fluvial Travertine From the Jiuzhaigou National Nature Reserve, Sichuan, Southwestern China

Abstract: The Jiuzhaigou National Nature Reserve on the Tibetan Plateau (Sichuan, southwestern China) is characterized by the deposition of fluvial travertine in a spectacular array of shoals, waterfalls, pool dams, and multicolored lakes. This is possibly the highest vegetated travertine setting of the world, from 2200 to 2900 m above sea level, an environment sensitive to minimal changes in temperature and precipitation regime. The evolution of the system is driven by two seasonal monsoon climate patterns with a wet spring–summer travertine deposition and then a dry fall–winter characterized by no precipitation or erosion. Spring and phreatic–vadose deposits transition from laminated columnar calcite to clotted micrite encrustation, possibly correlated with a mid-Holocene peak in precipitation and high lake levels in the northeastern Tibetan area connected to glacial advance. The most peculiar features are the fluvial shoals, a rather uncommon travertine surface consisting of two main superimposed facies of alternating weak- and strong-turbulence water flow. The low-turbulence facies consists of clotted micrite encrustation of mosses and cyanobacteria filaments, and platy calcite crystals covering algal filaments. The high-water-turbulence facies show seasonal alternation of diatom-rich bundles of Phormidium sp. (late spring) with algal Oocardium stratum levels (summer–fall). Upslope and downslope of the shoals, the precipitation of calcium carbonate results in the formation of prograding waterfalls and dam–pool systems that encrust macrophytes with microspar and clotted micrite. Encrusted chironomids larvae tubes are present in the waterfall walls up to an elevation of 2860 m, possibly the highest ever recorded. Early diagenetic processes such as dissolution of diatom frustules take place over the span of several years, a slower phenomenon compared to other travertine occurrences. In this high-elevation extreme setting, travertine sand and gravel bar deposits are produced by the exposure to severe weathering of a section of the valley that is bypassed through an underground karst system during the winter dry season. High-elevation travertine probably has a low preservation potential, but it appears to be more sensitive to climate changes than other depositional settings, especially in the Himalayan–Tibetan area, where the extent of the Quaternary glacial advances and retreats is still a matter of debate.

Seasonal pattern of population dynamics, spawning activities, and diet composition of sardine (Sardina pilchardus Walbaum) in the eastern Adriatic Sea

Monthly samples from commercial catches obtained with purse seiners operating in the Croatian fishing grounds (eastern Adriatic Sea) were collected throughout 2013, excluding January and December due to a fishing ban. Overall, 1010 sardine individuals were analyzed. Total body length ranged from 10.4 to 17.6 cm (mean ± SD: 13.9 ± 1.28 cm). Slightly larger individuals were caught during autumn at the beginning of the spawning season. Analysis of length-mass relationship showed that sardine specimens grow isometrically (b = 3.063). Seasonal oscillations of condition factor indicated that the examined specimens were in the best condition at the beginning of the spawning cycle. The analysis of stomach contents indicated that sardines preferred animal food (calanoid copepods, Oncaea spp., Farranula rostrata), although a plant component was also present (Bacillariophyceae). Seasonality was also observed in diet analysis, with diet changing in terms of feeding activity and prey quantity. The observed seasonal alternations of allometric condition factor and fullness index additionally confirmed that sardines were in the best condition at the beginning of the spawning season, for which they prepared themselves by higher feeding intensity, leading to higher storage of consumed energy.

Trophic structure of two intertidal Fucus spp. communities along a vertical gradient: Similarity and seasonal stability evidenced with δ13C and δ15N

Intertidal communities dominated by canopy-forming macroalgae typically exhibit some differences in their specific composition that are related to their location along the emersion gradient of rocky shores. Tidal level is also expected to affect resource availability for both primary producers and consumers, potentially leading to divergence in the trophic structure of these communities. Furthermore, in temperate areas, the alternation of seasons has usually a large influence on the primary production and on life-history traits of numerous species, which may induce some changes in the food webs of intertidal communities. Thus, this study aimed to investigate the trophic structure of two intertidal communities located at different tidal levels, over several seasons. Focusing on the dominant species of primary producers and consumers, the food webs of the Fucus vesiculosus Linnaeus and Fucus serratus Linnaeus communities were studied during four successive seasons, using an isotopic (δ13C and δ15N) approach. Due to the diversity of primary producers and consumers living in these two communities, food webs were relatively complex and composed of several trophic pathways. These food webs remained rather conserved over the successive seasons, even though some variability in isotopic signature and in diet has been highlighted for several species. Finally, despite their location at different tidal levels, the two Fucus spp. communities exhibited nearly the same trophic structure, with common consumer species displaying similar isotopic signature in both of them.

Patterns of Apoptosis and Proliferation throughout the Biennial Reproductive Cycle of Viviparous Female Typhlonectes compressicauda (Amphibia, Gymnophiona).

Typhlonectes compressicauda is an aquatic gymnophionan amphibian living in South America. Its breeding cycle is linked to seasons, characterized by a regular alternation of rainy and dry seasons. During a complex biennial cycle, the female genital tract undergoes a series of alternations of increasing and decreasing, governed by equilibrium of proliferation and apoptotic phenomena. Immunohistochemical methods were used to visualize cell proliferation with the detection of Ki67 antibody, a protein present in proliferative cells; terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Apostain were performed to detect apoptotic cells on sections of ovaries and oviducts. In ovaries, both phenomena affect the germinal nests and follicles according to the cycle period. In the oviduct, the balance was in favor of proliferation during preparation for reproduction, and in favor of apoptosis when genital ducts regress. Apoptosis and proliferation are narrowly implicated in the remodeling of the genital tract and they are accompanied by the differentiation of tissues according to the phase of the breeding cycle. These variations permit the capture of oocytes at ovulation, always at the same period, and the parturition after 6–7 months of gestation, at a period in which the newborns live with their mother, protected in burrows in the mud. During the intervening year of sexual inactivity, the female reconstitutes body reserves.

Sex allocation conflict between queens and workers in Formica pratensis wood ants predicts seasonal sex ratio variation.

Sex allocation theory predicts parents should adjust their investment in male and female offspring in a way that increases parental fitness. This has been shown in several species and selective contexts. Yet, seasonal sex ratio variation within species and its underlying causes are poorly understood. Here, we study sex allocation variation in the wood ant Formica pratensis. This species displays conflict over colony sex ratio as workers and queens prefer different investment in male and female offspring, owing to haplodiploidy and relatedness asymmetries. It is unique among Formica ants because it produces two separate sexual offspring cohorts per season. We predict sex ratios to be closer to queen optimum in the early cohort but more female-biased and closer to worker optimum in the later one. This is because the power of workers to manipulate colony sex ratio varies seasonally with the availability of diploid eggs. Consistently, more female-biased sex ratios in the later offspring cohort over a three-year sampling period from 93 colonies clearly support our prediction. The resulting seasonal alternation of sex ratios between queen and worker optima is a novel demonstration how understanding constraints of sex ratio adjustment increases our ability to predict sex ratio variation.

From the bush to the bench: the annual Nothobranchius fishes as a new model system in biology.

African annual fishes from the genus Nothobranchius are small teleosts that inhabit temporary water bodies subject to annual desiccation due to the alternation of the monsoon seasons. Given their unique biology, these fish have emerged as a model taxon in several biological disciplines. Their increasing popularity stems from the extremely short lifespan that is the result of their specific life-history adaptations and is retained under laboratory conditions. Nothobranchius furzeri, the most popular laboratory species, is the vertebrate species with the shortest lifespan recorded in captivity. In the laboratory, adults of different Nothobranchius species and populations live between 3 and 18 months and, notably, there is a negative correlation between the captive lifespan of a species and the aridity of their habitat. Their short lifespan is coupled to rapid age-dependent functional decline and expression of cellular and molecular changes comparable to those observed in other vertebrates, including humans. The recent development of transgenesis in this species makes it possible to insert specific constructs into their genome, and the establishment of transgenic lines is facilitated by their very rapid generation time, which can be as short as 1 month. This makes Nothobranchius species particularly suited for investigating biological and molecular aspects of ageing and ageing-associated dysfunctions. At the same time, they also represent a unique model taxon to investigate the evolution of life-history adaptations and their genetic architecture. We review their natural history, including phylogenetic relationships, distribution in relation to habitat conditions and natural selection for differential longevity, population structure and demography, and life cycle with emphasis on diapause that may occur at three stages during embryonic development. We further critically evaluate their use as a laboratory model for understanding the evolution of a rapid ageing rate and its consequences for other life-history traits, for cellular, molecular and integrative traits associated with the ageing process, high incidence of neoplasias, their utility for genome-wide gene-expression studies, and as a model for quantitative genetics. We summarize recent achievements in fostering Nothobranchius species as a widely applicable model system, including an annotated transcriptome, successful transgenesis, and existence of viable inbred lines. We compare the conditions they experience in the wild and in captivity and suggest that they are an ideal taxon to investigate natural genetic variation in a laboratory setting. We conclude that Nothobranchius species - and N. furzeri in particular - could become a unique model taxon that bridges interests in ecological and biomedical research. We hope that a conceptual and methodological integration of these two branches of biology will provide important new insights.

Assessing the hydrological impacts of agricultural changes upstream of the Tunisian World Heritage sea-connected Ichkeul Lake

Abstract. The impact of changes in agricultural land use and practices as a controlling driver of hydrologic response and as a source of diffuse pollution, are studied in the Joumine River basin, discharging into the Ichkeul Lake, northern Tunisia, a UNESCO World Heritage site since 1979. The lake is characterized by a very specific hydrological functioning based on a seasonal alternation of water levels and salinity through its link to the Mediterranean Sea. Three Landsat images, in situ surveys and SWAT modelling were used to simulate and assess streamflows and nitrate loads under retrospective land uses.

Seasonal differences in seismic responses of embankment on a sloping ground in permafrost regions

Because of its direct influence on the amount of unfrozen water and on the strength of intergranular ice in a frozen soil, temperature has a significant effect on all aspects of the mechanical behavior of the active layer in which temperature fluctuates above and below 0°C. Hence seismic responses of engineering structures such as embankment on a sloping ground in permafrost regions exhibit obvious differences with seasonal alternation. To explore the distinctive seismic characteristics of a railway embankment on the sloping ground in permafrost regions, a coupled water-heat-dynamics model is built based on theories of heat transfer, soil moisture dynamics, frozen soil mechanics, soil dynamics, and so on. A well-monitored railway embankment on a sloping ground in Qinghai–Tibet Plateau is taken as an example to simulate seismic responses in four typical seasons in the 25th service year. The numerical results show that seismic acceleration, velocity and displacement responses are significantly different in four typical seasons, and the responses on October 15 are much higher among the four seasons. When the earthquake is over, there are still permanent differential deformations in the embankment and even severe damages on the left slope on October 15. Therefore, this position should be monitored closely and repaired timely to ensure safe operation. In addition, the numerical model and results may be a reference for maintenance, design and study on other embankments in permafrost regions.