Reinitialization of evolutionary clocks during sublethal environmental stress in some invertebrates

This paper describes the influence of high environmental stress on evolutionary trends in some selected Mesozoic ammonite lineages and some protists. During extinction periods, many ammonoids are affected by drastic simplifications of their shell geometry, ornamentation and suture line. We observe that relatively tightly coiled ammonites can give rise to highly evolute forms or uncoiled heteromorphs with simple ornamentation and almost ceratitic suture line-a phenomenon called "proteromorphosis". Such simplifications often correspond to a reappearance of ancestral geometries (primitive ornamentation, evolute coiling or uncoiling) which suggest that the evolutionary clock of these organisms can be reinitialized by extreme, sublethal, environmental stress such as giant volcanism (including its consequences on diverse pollutions and on climatic changes) and major regressive events. (c) 2006 Elsevier B.V. All rights reserved.

A deep dig-hindsight on Holocene plant composition from ancient environmental DNA

Want a glimpse at past vegetation? Studying pollen and other plant remains, which are preserved for example in lake sediments or mires for thousands of years, allows us to document regional occurrences of plant species over radiocarbon-dated time series. Such vegetation reconstructions derived from optical analyses of fossil samples are inherently incomplete because they only comprise taxa that contribute sufficient amounts of pollen, spores, macrofossil or other evidences. To complement optical analyses for paleoecological inference, molecular markers applied to ancient DNA (aDNA) may help in disclosing information hitherto inaccessible to biologists. Parducci etal. (2013) targeted aDNA from sediment cores of two lakes in the Scandes Mountains with generic primers in a meta-barcoding approach. When compared to palynological records from the same cores, respective taxon lists show remarkable differences in their compositions, but also in quantitative representation and in taxonomic resolution similar to a previous study (JOrgensen etal. 2012). While not free of assumptions that need critical and robust testing, notably the question of possible contamination, this study provides thrilling prospects to improve our knowledge about past vegetation composition, but also other organismic groups, stored as a biological treasure in the ground.

Perceptual and semantic contributions to repetition priming of environmental sounds.

Repetition of environmental sounds, like their visual counterparts, can facilitate behavior and modulate neural responses, exemplifying plasticity in how auditory objects are represented or accessed. It remains controversial whether such repetition priming/suppression involves solely plasticity based on acoustic features and/or also access to semantic features. To evaluate contributions of physical and semantic features in eliciting repetition-induced plasticity, the present functional magnetic resonance imaging (fMRI) study repeated either identical or different exemplars of the initially presented object; reasoning that identical exemplars share both physical and semantic features, whereas different exemplars share only semantic features. Participants performed a living/man-made categorization task while being scanned at 3T. Repeated stimuli of both types significantly facilitated reaction times versus initial presentations, demonstrating perceptual and semantic repetition priming. There was also repetition suppression of fMRI activity within overlapping temporal, premotor, and prefrontal regions of the auditory "what" pathway. Importantly, the magnitude of suppression effects was equivalent for both physically identical and semantically related exemplars. That the degree of repetition suppression was irrespective of whether or not both perceptual and semantic information was repeated is suggestive of a degree of acoustically independent semantic analysis in how object representations are maintained and retrieved.

Genetic and environmental effects on the covariation betweencolour polymorphism and a life history trait

Variation in coloration with a strong underlying genetic basis is frequently found within animal populations but little is known about its function. Covariation between colour polymorphism and life-history traits can arise because morphs perform differently among environments or because they possess alternative alleles coding for key life-history traits. To test these two hypotheses, we studied a population of tawny owls Strix aluco, a bird displaying red, brown and grey morphs. We assessed the colour morph of breeding females, swapped eggs or hatchlings between pairs of nests, and examined how body condition in 3-week-old nestlings covaries with coloration of foster and genetic mothers. Redder foster and genetic mothers produced young in better condition. Because in two other years we observed that greyish females produced offspring in better condition than those of red females, the present study suggests that colour polymorphism signals genetic and phenotypic adaptations to cope with a fluctuating environment.

Phase 3 randomized trial on larynx preservation comparing sequential vs alternating chemotherapy and radiotherapy.

BACKGROUND: Both induction chemotherapy followed by irradiation and concurrent chemotherapy and radiotherapy have been reported as valuable alternatives to total laryngectomy in patients with advanced larynx or hypopharynx cancer. We report results of the randomized phase 3 trial 24954 from the European Organization for Research and Treatment of Cancer. METHODS: Patients with resectable advanced squamous cell carcinoma of the larynx (tumor stage T3-T4) or hypopharynx (T2-T4), with regional lymph nodes in the neck staged as N0-N2 and with no metastasis, were randomly assigned to treatment in the sequential (or control) or the alternating (or experimental) arm. In the sequential arm, patients with a 50% or more reduction in primary tumor size after two cycles of cisplatin and 5-fluorouracil received another two cycles, followed by radiotherapy (70 Gy total). In the alternating arm, a total of four cycles of cisplatin and 5-fluorouracil (in weeks 1, 4, 7, and 10) were alternated with radiotherapy with 20 Gy during the three 2-week intervals between chemotherapy cycles (60 Gy total). All nonresponders underwent salvage surgery and postoperative radiotherapy. The Kaplan-Meier method was used to obtain time-to-event data. RESULTS: The 450 patients were randomly assigned to treatment (224 to the sequential arm and 226 to the alternating arm). Median follow-up was 6.5 years. Survival with a functional larynx was similar in sequential and alternating arms (hazard ratio of death and/or event = 0.85, 95% confidence interval = 0.68 to 1.06), as were median overall survival (4.4 and 5.1 years, respectively) and median progression-free interval (3.0 and 3.1 years, respectively). Grade 3 or 4 mucositis occurred in 64 (32%) of the 200 patients in the sequential arm who received radiotherapy and in 47 (21%) of the 220 patients in the alternating arm. Late severe edema and/or fibrosis was observed in 32 (16%) patients in the sequential arm and in 25 (11%) in the alternating arm. CONCLUSIONS: Larynx preservation, progression-free interval, and overall survival were similar in both arms, as were acute and late toxic effects.

Population consequences of environmental sex reversal.

When sex determination in a species is predominantly genetic but environmentally reversible, exposure to (anthropogenic) changes in the environment can lead to shifts in a population's sex ratio. Such scenarios may be common in many fishes and amphibians, yet their ramifications remain largely unexplored. We used a simple model to study the (short-term) population consequences of environmental sex reversal (ESR). We examined the effects on sex ratios, sex chromosome frequencies, and population growth and persistence after exposure to environmental forces with feminizing or masculinizing tendencies. When environmental feminization was strong, X chromosomes were driven to extinction. Analogously, extinction of normally male-linked genetic factors (e.g., Y chromosomes) was caused by continuous environmental masculinization. Although moderate feminization was beneficial for population growth in the absence of large viability effects, our results suggest that the consequences of ESR are generally negative in terms of population size and the persistence of sex chromosomes. Extreme sex ratios resulting from high rates of ESR also reduced effective population sizes considerably. This may limit any evolutionary response to the deleterious effects of ESR. Our findings suggest that ESR changes population growth and sex ratios in some counter-intuitive ways and can change the predominant factor in sex determination from genetic to fully environmental, often within only a few tens of generations. Populations that lose genetic sex determination may quickly go extinct if the environmental forces that cause sex reversal cease.

Evaluation of occupational exposure: comparison of biological and environmental variabilities using physiologically based toxicokinetic modeling

PURPOSE: Few studies compare the variabilities that characterize environmental (EM) and biological monitoring (BM) data. Indeed, comparing their respective variabilities can help to identify the best strategy for evaluating occupational exposure. The objective of this study is to quantify the biological variability associated with 18 bio-indicators currently used in work environments. METHOD: Intra-individual (BV(intra)), inter-individual (BV(inter)), and total biological variability (BV(total)) were quantified using validated physiologically based toxicokinetic (PBTK) models coupled with Monte Carlo simulations. Two environmental exposure profiles with different levels of variability were considered (GSD of 1.5 and 2.0). RESULTS: PBTK models coupled with Monte Carlo simulations were successfully used to predict the biological variability of biological exposure indicators. The predicted values follow a lognormal distribution, characterized by GSD ranging from 1.1 to 2.3. Our results show that there is a link between biological variability and the half-life of bio-indicators, since BV(intra) and BV(total) both decrease as the biological indicator half-lives increase. BV(intra) is always lower than the variability in the air concentrations. On an individual basis, this means that the variability associated with the measurement of biological indicators is always lower than the variability characterizing airborne levels of contaminants. For a group of workers, BM is less variable than EM for bio-indicators with half-lives longer than 10-15 h. CONCLUSION: The variability data obtained in the present study can be useful in the development of BM strategies for exposure assessment and can be used to calculate the number of samples required for guiding industrial hygienists or medical doctors in decision-making.

Coexistence of specialist and generalist species is shaped by dispersal and environmental factors.

Disentangling the mechanisms mediating the coexistence of habitat specialists and generalists has been a long-standing subject of investigation. However, the roles of species traits and environmental and spatial factors have not been assessed in a unifying theoretical framework. Theory suggests that specialist species are more competitive in natural communities. However, empirical work has shown that specialist species are declining worldwide due to habitat loss and fragmentation. We addressed the question of the coexistence of specialist and generalist species with a spatially explicit metacommunity model in continuous and heterogeneous environments. We characterized how species' dispersal abilities, the number of interacting species, environmental spatial autocorrelation, and disturbance impact community composition. Our results demonstrated that species' dispersal ability and the number of interacting species had a drastic influence on the composition of metacommunities. More specialized species coexisted when species had large dispersal abilities and when the number of interacting species was high. Disturbance selected against highly specialized species, whereas environmental spatial autocorrelation had a marginal impact. Interestingly, species richness and niche breadth were mainly positively correlated at the community scale but were negatively correlated at the metacommunity scale. Numerous diversely specialized species can thus coexist, but both species' intrinsic traits and environmental factors interact to shape the specialization signatures of communities at both the local and global scales.

Genetic and maternal contributions to offspring viability under different environmental conditions in various salmonids

Summary : Due to anthropogenic impacts and natural fluctuations, fish usually have to cope with constantly changing and often hostile environments. Whereas adult fish have various possibilities to counteract unfavourable environmental conditions, embryos have much fewer options. Besides by their developing immune system, they are protected by the egg envelopes and several immune substances provided by their mothers. In addition to this, they may also adjust their hatching timing in reaction to various risks. However, individuals may vary in their defensive potential. This variation may be either based on their genetics and/or on differential maternal investments and may be dependent on the experienced stress. Nevertheless, in fish, the impact of such parental contributions on embryo and/or juvenile viability is still poorly investigated. The main objective of this thesis was to investigate the importance of paternal (i.e. genetic) and maternal (i.e. genetic + egg investment) contributions to offspring viability under different environmental conditions and at different life stages. In order to investigate this, we used gametes of various salmonids for in vitro fertilisation experiments based on full-factorial breeding designs. The individual studies are summarised in the following chapters: In the first chapter, we tested the effectiveness of the embryonic immune system in Lake whitefish (Coregonus palaea). Namely, we investigated paternal and maternal contributions to the embryos' tolerance to different kinds of pathogen exposure. Additionally, we tested whether an early sub-léthal exposure has a positive or a negative effect on an embryo's susceptibility to later pathogen exposures with the same pathogen. We found that pre-challenged embryos were more susceptible to future challenges. Moreover, pathogen susceptibility was dependent on maternal investments and/or the embryos' own genetics, depending on the challenge level. Chapter 2 summarises a similar study with brown trout (Salmo trutta). In addition to the previously described investigations, we analysed if genetic effects on offspring viability are mediated either by parental MHC genotypes or relatedness based on neutral microsatellite markers, and we tested if males signal their genetic quality either by their body size or their melanin-based skin colouration. We found that embryo survival was lower at higher stress levels and dependent on the embryos' genetics. Addirionally, parents with similar and/or, very common MHC genotypes had higher offspring viabilities. Finally, darker males produced more viable offspring. In the first two chapters we investigated the embryos' defensive potential based on their immune system, i.e. their pathogen tolerance. In chapter 3 we investigate whether hatching timing of Lake whitefìsh (C. palaea) is dependent on parental contributions and/or on pathogen pressure, and whether there are parental-environmental interactions. We found that whitefish embryos hatch earlier under increasing pathogen pressure. Moreover, hatching timing was affected by embryo genetics and/or maternally provided resources, but the magnitude of the effect was dependent on the pathogen. pressure. We also found a significant paternal-environmental interaction, indicating that the hatching efficiency of a certain sib group is dependent on the pathogen environment. Chapter 4 describes an analogous study with brown trout (S. trutta), with similar findings. In the former chapters, we only looked at offspring performance during the embryonic period, and only under semi-natural conditions. In chapter 5 we now test the performance and viability of embryonic and juvenile brown trout (S. trutta) under natural conditions. To measure embryo viability, we put them in brood boxes, buried them in the gravel of a natural river, and analysed survival after several months. To investigate juvenile survival and performance, wé reared embryos under different stress levels in the laboratory and subsequently released the resulting hatchlings in to a closed river section. Juvenile size and survival was then determined one year later. Additionally, we investigated if sires differ in their genetic quality, determined by embryo and juvenile survival as well as juvenile size, and if they signal their quality by either body size or melanin-based body darkness. We found hat juvenile size was dependent on genetic effects and on maternal investment, whereas this was neither the case for embryo nor for juvenile survival. Additionally, we found that offspring of darker males grew larger, and larger juveniles had also an increased survival. Finally, we found acarry-over effect of the early non-lethal challenge: exposing embryos to higher stress levels resulted in smaller juveniles. To evaluate the long-term performance of differently treated groups, mark-recapture studies are inevitable. For this purpose, effective mass-marking techniques are essential. In chapter 6 we tested the suitability of the fluorescent pigment spray marking method for the mass marking of European graylings (Thymallus thymallus), with very promising results. Our in vitro fertilisation studies on whitefish may reveal new insights on potential genetic benefits of mate choice, but the mating system of whitefish under natural conditions is still poorly investigated. In order to study this, we installed underwater cameras at the spawning place of a Coregonus suidteri population, recorded the whole mating period and subsequently analysed the recordings. Confirmations of previous findings as well as exciting new observations are listed and discussed in chapter 7. Dus aux impacts anthropogéniques et aux fluctuations naturelles, les poissons doivent faire face à des environnements en perpétuel changement. Ces changements font que les poissons doivent s'adapter à de nouvelles situations, souvent hostiles pour eux. Les adultes ont différentes possibilités d'échapper à un environnement peu favorable, ce n'est par contre pas le cas des embryons. Les embryons sont protégés d'une part par leur système immunitaire en développement, d'autre part, par la coquille de l'eeuf et différentes substances immunitaires fournies par leur mère. De plus, ils sont capables d'influencer leur propre date d'éclosion en réponse à différents facteurs de stress. Malgré tout, les individus varient dans leur capacité à se défendre. Cette variation peut être basé sur des facteurs génétiques et/ou sur des facteurs maternels, et est dépendante du stress subi. Néanmoins, chez les poissons, l'impact de telles contributions parentales sur la survie d'embryons et/ou juvéniles est peu étudié. L'objectif principal de cette thèse a été d'approfondir les connaissances sur l'importance de la contribution paternelle (c.a.d. génétique) et maternelle (c.a.d. génétique + investissement dans l'oeuf) sur la survie des jeunes dans différentes conditions expérimentales et stades de vie. Pour faire ces analyses, nous avons utilisé des gamètes de divers salmonidés issus de croisements 'full-factorial'. Les différentes expériences sont résumées dans les chapitres suivants: Dans le premier chapitre, nous avons testé l'efficacité du système immunitaire des embryons chez les corégones (Coregonus palea). Plus précisément nous avons étudié la contribution paternelle et maternelle à la tolérance des embryons à différents niveaux de stress pathogène. Nous avons aussi testé, si une première exposition non létale à un pathogène avait un effet positif ou négatif sur la susceptibilité d'un embryon a une deuxième exposition au même pathogène. Nous avons trouvé que des embryons qui avaient été exposés une première fois étaient plus sensibles au pathogène par la suite. Mais aussi que la sensibilité au pathogène était dépendante de l'investissement de la mère et/ou des gènes de l'embryon, dépendamment du niveau de stress. Le deuxième chapitre résume une étude similaire avec des truites (Salmo truffa). Nous avons examiné, si la survie des jeunes variait sous différentes intensités de stress, et si la variance observée était due aux gènes des parents. Nous avons aussi analysé si les effets génétiques sur la survie des juvéniles étaient dus au MHC (Major Histocompatibility Complex) ou au degré de parenté des parents. De plus, nous avons analysé si les mâles signalaient leur qualité génétique par la taille du corps ou par leur coloration noire, due à la mélanine. On a trouvé que la survie des embryons était plus basse quand le niveau de stress était plus haut mais que la variation restait dépendante de la génétique des embryons. De plus, les parents avec des MHC similaires et/ou communs avaient des embryons avec une meilleure survie. Par contre, des parents avec un degré de parenté plus haut produisent des embryons avec une survie plus mauvaise. Finalement nous avons montré que les mâles plus foncés ont des embryons qui survivent mieux, mais que la taille des mâles n'a pas d'influence sur la survie de ces mêmes embryons. Dans les deux premiers chapitres, nous avons étudié le potentiel de défense des embryons basé sur leur système immunitaire, c.a.d. leur tolérance aux pathogènes. Dans le troisième chapitre, nous nous intéressons à la date d'éclosion des corégones (C. palea), pour voir si elle est influencée par les parents ou par la pression des pathogènes, et si il y a une interaction entre ces deux facteurs. Nous avons trouvé que les jeunes naissent plus rapidement lorsque la pression en pathogènes augmente. La date d'éclosion est influencée par la génétique des embryons et/ou l'investissement des parents, mais c'est la magnitude des effets qui est dépendante de la pression du pathogène. Nous avons aussi trouvé une interaction entre l'effet paternel et l'environnement, ce qui indique que la rapidité d'éclosion de certains croisements est dépendante des pathogènes dans l'environnement. Le chapitre 4 décrit une étude analogue avec de truites (S. truffa), avec des résultats sitzimilaires. Dans les précédents chapitres nous nous sommes uniquement concentrés sur les performances des jeunes durant leur stade embryonnaire, et seulement dans des conditions semi naturelles. Dans le chapitre 5 nous testons la performance et la viabilité des embryons et de juvéniles de truites (S. truffa) dans des conditions naturelles. Nous avons trouvé que la taille des juvéniles était dépendante d'effets génétiques et de l'investissement maternel, mais ceci n'était ni les cas pour les survie des embryons et des juvéniles. De plus, nous avons trouvé que les jeunes des mâles plus foncés devenaient plus grands et que les grands ont un meilleur taux de survie. Finalement nous avons trouvé un 'carry-over effect' d'une première exposition non létale à un pathogène: exposer des embryons à des plus hauts niveaux de stress donnait des juvéniles plus petits. Pour évaluer la performance à long terme de groupes traités dé manières différentes, une méthode de marquage-recapture est inévitable. Pour cette raison, des techniques de marquage en masse sont nécessaires. Dans le chapitre 6, nous avons testé l'efficacité de la technique `fluorescent pigment spray marking' pour le marquage en masse de l'Ombre commun (Thymallus thymallus), avec des résultats très prometteurs. Les études de fertilisations in vitro avec les corégones nous donnent une idée du potentiel bénéfice génétique que représente la sélection d'un bon partenaire, même si le système d'accouplement des corégones en milieu naturel reste peu connu. Pour combler cette lacune, nous avons installé des caméras sous-marines autour de la frayère d'une population de corégones (C. suidteri), nous avons enregistré toute la période de reproduction et nous avons analysé les données par la suite. Ainsi, nous avons été capables de confirmer bien des résultats trouvés précédemment, mais aussi de faire de nouvelles observations. Ces résultats sont reportés dans le septième chapitre, où elles sont comparées avec des observations antérieures.

Impact of biological and environmental variabilities on biological monitoring: an approach using toxicokinetic models

Biological monitoring of occupational exposure is characterized by important variability, due both to variability in the environment and to biological differences between workers. A quantitative description and understanding of this variability is important for a dependable application of biological monitoring. This work describes this variability,using a toxicokinetic model, for a large range of chemicals for which reference biological reference values exist. A toxicokinetic compartmental model describing both the parent compound and its metabolites was used. For each chemical, compartments were given physiological meaning. Models were elaborated based on physiological, physicochemical, and biochemical data when available, and on half-lives and central compartment concentrations when not available. Fourteen chemicals were studied (arsenic, cadmium, carbon monoxide, chromium, cobalt, ethylbenzene, ethyleneglycol monomethylether, fluorides, lead, mercury, methyl isobutyl ketone, penthachlorophenol, phenol, and toluene), representing 20 biological indicators. Occupational exposures were simulated using Monte Carlo techniques with realistic distributions of both individual physiological parameters and exposure conditions. Resulting biological indicator levels were then analyzed to identify the contribution of environmental and biological variability to total variability. Comparison of predicted biological indicator levels with biological exposure limits showed a high correlation with the model for 19 out of 20 indicators. Variability associated with changes in exposure levels (GSD of 1.5 and 2.0) is shown to be mainly influenced by the kinetics of the biological indicator. Thus, with regard to variability, we can conclude that, for the 14 chemicals modeled, biological monitoring would be preferable to air monitoring. For short half-lives (less than 7 hr), this is very similar to the environmental variability. However, for longer half-lives, estimated variability decreased. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: tables detailing the CBTK models for all 14 chemicals and the symbol nomenclature that was used.] [Authors]

Developmental and Environmental Regulation of Aquaporin Gene Expression across Populus Species: Divergence or Redundancy?

Aquaporins (AQPs) are membrane channels belonging to the major intrinsic proteins family and are known for their ability to facilitate water movement. While in Populus trichocarpa, AQP proteins form a large family encompassing fifty-five genes, most of the experimental work focused on a few genes or subfamilies. The current work was undertaken to develop a comprehensive picture of the whole AQP gene family in Populus species by delineating gene expression domain and distinguishing responsiveness to developmental and environmental cues. Since duplication events amplified the poplar AQP family, we addressed the question of expression redundancy between gene duplicates. On these purposes, we carried a meta-analysis of all publicly available Affymetrix experiments. Our in-silico strategy controlled for previously identified biases in cross-species transcriptomics, a necessary step for any comparative transcriptomics based on multispecies design chips. Three poplar AQPs were not supported by any expression data, even in a large collection of situations (abiotic and biotic constraints, temporal oscillations and mutants). The expression of 11 AQPs was never or poorly regulated whatever the wideness of their expression domain and their expression level. Our work highlighted that PtTIP1;4 was the most responsive gene of the AQP family. A high functional divergence between gene duplicates was detected across species and in response to tested cues, except for the root-expressed PtTIP2;3/PtTIP2;4 pair exhibiting 80% convergent responses. Our meta-analysis assessed key features of aquaporin expression which had remained hidden in single experiments, such as expression wideness, response specificity and genotype and environment interactions. By consolidating expression profiles using independent experimental series, we showed that the large expansion of AQP family in poplar was accompanied with a strong divergence of gene expression, even if some cases of functional redundancy could be suspected.

Environmental stress and atavism in ammonoid evolution

The most common trends observed in ammonoid evolution during ecologically stable periods are characterized by an increase of shell curvature (e.g. evolute to involute), by the development of more complex ornamentation (flexuosity of ribbing, appearance of nodes and spines) and by a long term increase of the suture line's fractal dimension. Major evolutionary jumps in ammonoids occur during severe extinction events, and are characterized by the sudden appearance of simple, primitive-looking forms which are similar to remote ancestors of their more complex immediate progenitors. Such forms are interpreted as atavistic. According to this hypothesis, homeomorphic species generated during such sublethal stress events can be separated by several millions of years.

Influence of the menstrual cycle on the sweating response measured by direct calorimetry in women exposed to warm environmental conditions.

The whole body sweating response was measured at rest in eight women during the follicular (F) and the luteal (L) phases of the menstrual cycle. Subjects were exposed for 30-min to neutral (N) environmental conditions [ambient temperature (Ta) 28 degrees C] and then for 90-min to warm (W) environmental conditions (Ta, 35 degrees C) in a direct calorimeter. At the end of the N exposure, tympanic temperature (Tty) was 0.18 (SEM 0.06) degrees C higher in the L than in the F phase (P less than 0.05), whereas mean skin temperature (Tsk) was unchanged. During W exposure, the time to the onset of sweating as well as the concomitant increase in body heat content were similar in both phases. At the onset of sweating, the tympanic threshold temperature (Tty,thresh) was higher in the L phase [37.18 (SEM 0.08) degrees C] than in the F phase [36.95 (SEM 0.07) degrees C; P less than 0.01]. The magnitude of the shift in Tty,thresh [0.23 (SEM 0.07) degrees C] was similar to the L-F difference in Tty observed at the end of the N exposure. The mean skin threshold temperature was not statistically different between the two phases. The slope of the relationship between sweating rate and Tty was similar in F and L. It was concluded that the internal set point temperature of resting women exposed to warm environmental conditions shifted to a higher value during the L phase compared to the F phase of the menstrual cycle; and that the magnitude of the shift corresponded to the difference in internal temperature observed in neutral environmental conditions between the two phases.

Paleoenvironmental evolution of the Helvetic shallow-water carbonate platform near the Barremian-Aptian boundary, and its relationship with paleoceanographic and paleoclimatic change in the Tethys

Abstract:During my doctoral research, I focused on deciphering the interactions between sea-level and climate change during the Late Barremian-Early Aptian, their expression in the Tethys basin and in the Helvetic carbonate platform. The research highlights are summarized here in three points: In the Helvetic Alps, the transition between the Lower Schrattenkalk (Upper Barremian) and the Rawil Member (Lowermost Aptian) is characterized by a change from a predominantly photozoan to a heterozoan carbonate-producing system, which coincides in time with a general increase in detrital and nutrient input. The clay mineral record shows the appearance of kaolinite within the Rawil Member, whereas this mineral is absent from the uppermost Lower and lowermost Upper Schrattenkalk Members. This indicates the installation of a warmer and more humid climate during this time period. A negative peak in 513C is recorded at the top of the Lower Schrattenkalk Member, and correlates with the well-known negative excursion of -l%o occurring in other basins and dated as latest Barremian, thus confirming a latest Barremian and earliest Aptian age for the Lower Schrattenkalk and Rawil Members, respectively. Furthermore, a sequence stratigraphie framework has been defined for the Rawil Member, based on both the ecology of faunal and floral assemblages, and their palaeoenvironmental interpretation, as well as on the stacking pattern of limestone beds observed during field prospection. The presence of a sequence boundary is postulated near the top of the Lower Schrattenkalk Member, which is correlated with the earliest Aptian SbAl defined in Vercors (France). The SbAl is characterized by a maximum of proximal assemblages and by the disappearance of several benthic foraminiferal species. Within the Rawil Member itself, the stacking pattern and microfacies trends are interpreted to represent the TST of the first Aptian sequence. With regards to the pelagic setting in the Tethyan realm, I investigated the Gorgo a Cerbara section (central Italy). There, thin organic-rich layers occur episodically in pelagic carbonates of the upper Barremian portion of the Maiolica Formation. They are associated with high Corg:Ptot ratios, which indicate the presence of intermittent dysoxic to anoxic conditions. Coarse correlations are also observed between TOC, Ρ and biogenic silica contents, indicating links between Ρ availability, productivity, and organic matter preservation. The corresponding 813Ccarb and δ180 records remain, however, quite stable, indicating that these brief periods of enhanced TOC preservation did not have sufficient impact on the marine carbon household to deviate 6,3C records, and are probably not the consequence of major climate change. On the other hand, organic-rich layers become more frequent around the Barremian-Aptian boundary in both pelagic and hemi-pelagic environments (Gorgo a Cerbara and La Bédoule, France), which are correlated with negative excursions in 6l3Ccarb and 613Corg records. During the earliest Aptian, at Gorgo a Cerbara, the frequency of organic-rich intervals progressively increases and redox-sensitive trace-element enrichments become more frequent, until the highest TOC-enriched level just below the "Livello Selli", indicator of Oceanic Anoxic Event la (OAEla). The latter is associated with the well-known negative spike in 613Ccarb and S,3Corg records, a diminution in the δ,80 record interpreted as the consequence of a wanning interval, an important peak in Ρ accumulation and high Cor::Ptot ratios indicating the prevalence of anoxic conditions. The Selli Level (OAEla) documents a general cooling phase and coincides with maximum RSTE enrichments as well as high Corg:Ptot ratios, which confirm the importance of anoxic conditions during OAE1 a at this site.During the Early Aptian, environmental change on the platform is expressed by orbitolinids proliferation that may be induced by both climate change and sea-level rise. In the basin, the successive black shales horizons from the Late Barremian until the OAE la are interpreted as the progressive impact of palaeoenvironmental change probably linked to the formation of the Ontong- Java plate-basalt plateau.RésuméCe travail de thèse a permis d'investiguer les interactions entre les variations du niveau marin et les changements climatiques sur la plate-forme helvétique ainsi qu'en domaine pélagique à la limite Barrémien-Aptien (Crétacé).Dans les Alpes helvétiques, la limite Barrémien-Aptien est marquée par la transition du Schrattenkalk inférieur, caractérisé par des carbonates photozaires, au Membre de Rawil caractérisé par des carbonates héterozoaires. Cette transition est marquée par une arrivée massive d'éléments détritiques et un apport de nutriments ayant entraîné la prolifération de foraminifères agglutinés tels que les orbitolines. L'analyse des minéraux argileux indique l'apparition de la kaolinite durant le Membre de Rawil, interprétée comme l'installation d'un climat plus chaud et humide. Un pic négatif en 513C est enregistré au sommet du Schrattenkalk inférieur correspond à l'excursion négative de -1%0 bien connue en domaine pélagique et datée comme Barrémien terminal. Cette corrélation apporte un contrôle chronostratigraphique supplémentaire permettant de dater le Schrattenkalk inférieur du Barrémien sup. et le Membre de Rawil de l'Aptien inf. D'autre part, une étude stratigraphique, basée sur des observations de terrain et sur l'interprétation d'assemblages floristiques et faunistiques en terme de paléoenvironnement a permis de mettre en évidence une limite de séquence au sommet du Schrattenkalk inf., corrélable avec la SbAl définie dans le Vercors. Durant la mise en place du Membre de Rawil, l'évolution des microfaciès est interprétée comme le « Transgressive System Tract » de la première séquence aptienne.En domaine pélagique, de minces couches riches en matière organique (MO) apparaissent dès le Barrémien sup. dans la coupe de Gorgo a Cerbara (Italie). Elles sont associées à un ratio C:P élevé indiquant des conditions épisodiquement dysoxiques à anoxiques. De plus, une corrélation nette entre Carbone Organique Total (TOC), phosphore (P) et silice biogénique est observée correspondant à un lien entre Ρ disponible, productivité et préservation de la MO. Pourtant, dans le même temps, le ÔI3C et le δ1βΟ restent constants indiquant des conditions environnementales stables et un cycle du carbone non perturbé par la préservation de MO qui ne serait pas la conséquence d'un changement climatique global mais juste d'un effet local.Ala limite Barrémien-Aptien, en domaine hémi-pélagique (La Bédoule, France) et pélagique (Gorgo a Cerbara), les couches riches en MO sont plus fréquentes et plus épaisses, elles se sont déposées en même temps qu'un pic négatif en 513CCARB et ô13Coib probablement dû à un épisode volcanique. A l'Aptien inf. le TOC des niveaux riches en MO augmente progressivement en même temps que la teneur en éléments traces jusqu'au dernier enrichissement avant l'événement anoxique océanique la (OAE la) correspondant au « niveau critique inf. », indiquant des conditions anoxiques moins restreintes. Celui-ci est également caractérisé par le fameux pic négatif en Ô13C (C3), une diminution du δ180 interprétée comme un réchauffement, par un pic en Ρ et un ratio C:P élevé. L'OAE 1 a, quant à lui, enregistre un refroidissement et coïncide avec le maximum en éléments traces ainsi qu'un fort ratio C:P mettant en valeur l'importance des conditions anoxiques pendant 1ΌΑΕ la dans cette coupe alors qu'aucune perturbation n'est enregistrés à La Bédoule probablement à cause de conditions paléogéographiques locales.Durant l'Aptien inf., les changements environnementaux sur la plate-forme se marquent par la prolifération d'orbitolines due à un changement climatique et une hausse du niveau marin. En domaine profond, la succession de niveaux riches en MO du Barrémien sup. jusqu'à l'OAE la documente l'impact progressif de changements paléoenvironnementaux, probablement liés à la formation du plateau d'Ontong Java à l'ouest de l'océan Pacifique.