L’étude des conséquences du réchauffement climatique sur les écosystèmes aquatiques est devenue un enjeu majeur pour la recherche. Nous avons mesuré l’impact de la température des eaux douces et du changement de végétation riparienne associé au climat sur six populations de Gammarus pulex (Amphipode) vivant au nord ou au sud de la vallée du Rhône (France). Ce crustacé, largement répandu dans les eaux douces européennes, est considéré comme une espèce clé pour le fonctionnement des écosystèmes aquatiques, car, en dégradant la litière de feuilles provenant de la ripisylve, il favorise son utilisation par d’autres invertébrés. Nos résultats sur l’effet de la température sur les réserves énergétiques, la consommation d’oxygène et la survie, suggèrent que la fenêtre thermique optimale est décalée de 2-3°C entre les gammares du nord et ceux du sud. L’investissement reproducteur varie saisonnièrement, avec des stratégies différentes selon l’origine des femelles. La provenance des feuilles (méditerranéenne/continentale) influence moins leur conditionnement et la vitesse de décomposition que leur dureté initiale. Une hausse de température accélère le conditionnement et la digestion des feuilles mais influence peu leur dégradation. Nos résultats montrent que des adaptations en bordure d’aire de distribution peuvent modifier la réponse des organismes aquatiques face aux changements climatiques. De plus, un changement de la nature des litières lié au réchauffement pourrait modifier la disponibilitédes ressources trophiques au cours des saisons et ainsi le fonctionnement des écosystèmes. / The study of global warming consequences on aquatic ecosystems has become amajor issue in current scientific research. We measured the impact of water temperature and the climate-related change in riparian vegetation on six populations of Gammarus pulex (Amphipoda) living in the North and in the South of the Rhône River valley (France). This crustacean, widely distributed in European freshwaters, is considered as a key species for the freshwater ecosystems functioning as it degrades the leaf litter from the riparian area, thus favouring its subsequent use by other invertebrates. Our results of temperature effect onenergy stores, oxygen consumption, and survival suggest that the optimal thermal window shifts from 2-3°C between northern and southern gammarids. Females’ investment into reproduction changes through seasons, with different strategies according to their geographical origins. Concerning the functional point of view, the leaf litter origin(Mediterranean/continental) less influences the conditioning of leaves and the decomposition rate than their initial toughness. An increase in water temperature accelerates the conditioning and the enzymatic digestion of leaves (in gammarids guts) but slightly influences their degradation by this crustacean. Our results show that adaptations at the limit of the species geographical distribution area can change the response to climate change in aquatic organisms. Moreover, a change in the type of the leaf litter could modify the availability of trophic resource through seasons and hence the ecosystem functioning.

Invasion physiology is an emerging field that endeavors to understand the influence of physiological traits on the establishment of non-native species in novel environments. The invasive European green crab,Carcinus maenas, is one of the world's most successful aquatic invaders, and is currently distributed across temperate marine ecosystems globally. The work presented here explored the thermal physiology of this species, and has highlighted several physiological traits that have likely influenced establishment success. Intraspecific comparisons of crabs sampled from the northern and southern edges of their recipient, or invaded range on the west coast of North America have identified both organismal and cellular physiological difference with respect to upper and lower thermal tolerances. Crabs sampled from British Columbia, Canada (BC) had a significantly lower mean upper thermal tolerance threshold and heat shock protein synthesis, Hsp70, compared to their warm acclimated conspecifics sampled from California (CA). These differential physiologic responses may be rooted in the disparate natural thermal habitats that each population occupies within their respective environments. The ability of this species to extend its current range limits was also investigated. Range expansion to the south has been limited, and is likely restricted by this species lack of adaptation to warmer temperatures. Because range expansion has been chiefly northward, characterizing this species' response to cold stress can identify whether colder temperatures poleward may limit further range expansion. Cold tolerance capacity was determined in the laboratory, and crabs sampled from Vancouver Island, British Columbia were able to withstand the over-wintering thermal regime that occurs in Sitka, Alaska, a site that is currently beyond the range limits of this species. Furthermore, intraspecific assessments found that the cold acclimated BC population exposed to cold shock significantly down regulated protein levels of cyclin D1, cell cycle modulator. Distinct differences in carapace width (CW) were detected along the thermal gradient present in the green crabs' range. This variation in body size was utilized to the test the temperature size rule hypothesis for ectotherms. Simply stated, the temperature size rule is the tendency for ectotherms to develop slower but mature to a larger body sizes at cooler temperatures. The results supported this hypothesis as crabs sampled from the warm portion of the range were found to be smaller than crabs sampled from the colder portion of the range. This pattern was detected along the native range as well. Differences in body size have the potential to influence the scope of invasion; larger individuals are generally more fecund and longer lived, which can increase both the intensity and frequency of larval dispersal that could further propel range expansion. The physiologic properties that the green crab possesses which may influence invasion success were examined using peer-reviewed literature with the aim of determining if these physiological traits confer invasion success across taxa. This analysis tested four hypotheses: 1) Broad geographic temperature tolerances (thermal width) confer a higher upper thermal tolerance threshold when comparing invasive and native species. 2) The upper thermal extreme experienced in nature is correlated with upper thermal tolerance threshold. 3) Protein chaperone expression, a cellular mechanism underlying thermal tolerance threshold, is greater in invasive organisms than in native ones. 4) Acclimation to higher temperatures can promote a greater range of thermal tolerance for invasives compared to natives. These preliminary results generally support the four stated hypotheses, and provide a solid foundation for further studies to explore and identify physiologic traits that facilitate invasion success. Overall, these studies investigated the thermal physiology ofCarcinus maenasfrom an invasive metapopulation and have brought about significant advances in our understanding of what physiologic traits correlate to invasion success in this species. In addition, the data presented here can aid resource managers in identifying habitats, based on thermal tolerance measurements that fit the criteria for invasion. Understanding how invasive organisms vary with respect to thermal tolerance can aid our understanding the patterns and processes of species invasions.

As a unique habitat that encompasses steep environmental gradients, it is important to evaluate threats posed to the intertidal zone by rapid climate change. It is thought that intertidal ectotherms are living close to their physiological limit; therefore slight changes in temperature could result in high levels of mortality. Past studies on intertidal species measured thermal tolerance under constant temperatures, neglecting to consider the impacts of natural variation in field temperatures. I conducted a study on the barnacle, Balanus glandula, to assess if a variable thermal environment would alter thermal tolerance. Barnacles were acclimated in an intertidal mesocosm to either daily cold (maximum 20.4◦C), daily warm (maximum 26.5◦C), or variable (two days cold, two days warm) low-tide temperatures. I measured each barnacle’s critical thermal maximum (CTmax) by increasing air temperature 6◦C/hour and identifying the point at which the barnacle ceased to function. Barnacles exposed to any warm temperatures demonstrated an increased thermal tolerance, suggesting that this population of barnacles is capable of shifting their thermal maximum. Furthermore, acclimation to thermal heterogeneity raised thermal maximum, reinforcing the need for future thermal tolerance studies to incorporate biologically-relevant thermal regimes in laboratory experiments. These results demonstrate that B. glandula in the field are well-adapted for increasing air temperatures.

In the present M. Sc. thesis the effect of water temperature (thermal range: 17.4 - 38.6 °C) on early life history (during interval from egg fertilization to full yolk sac depletion by 50 % of larvae; Fe - Re50) in African catfish (Clarias gariepinus) was examined. Length of the incubation period (i. e. interval from egg fertilization to the moment of hatching of 50 % of individuals; Fe - H50), length of the hatching period (i. e. interval from hatching of 5 % of individuals to hatching of 95 % of individuals; H5 - H95), length of the period up to the first intake of exogenous food (i. e. interval from H50 to the first intake of exogenous food by 50 % of individuals; H50 - S50) and length of the period up to the full yolk sac resorption (H50 - Re50) were inversely proportional to the incubation temperature. Period of the yolk sac resorption was significantly prolonged (approximately six times) because of using of exogenous food (compared to treatments without added external food supplies). Embryonic development was theoretically stopped at temperature 15.4 °C and hatching occured after c. 12 effective day-degrees. Size of larvae increased during embryonic and larval period. Size of larvae at H50, S50 and Re50, was inversely proportional dependent on the incubation temperature. Size of individuals at Re50 was increased (approximately twice) because of using of exogenous food (compared to treatments without added external food supplies). Yolk sac volume (YsV) decreased during embryonic and larval period. YsV at H50 was correlated with size of egg and YsV was S50 was inversely proportional to the incubation temperature. A dry weight of yolk sac at H50 represented c. 89 % of total dry weight of hatched larvae. During the period of endogenous feeding c. 75 % of dry weight of egg was converted into the larval somatic tissues. Efficiency of energy conversion during the period of endogenous feeding is lower (60 %). The energetical value of total dry matter and content of sulfur in dry matter was decreasing during the period of endogenous feeding (in order: egg, hatched larvae, larvae at Re50). Content of nitrogen and carbon in dry matter was increasing during the embryonic period and afterwards was decreasing during the larval period. In term of survival, the zone of thermal tolerance for early life history in African catfish ranges from 19 to 33 °C (with thermal optimum between 23 and 30 °C), i. e. this fish belongs to the typical thermophilous species. The suboptimal temperatures lies within intervals 21 - 23 °C and 30 - 33 °C, respectively. Temperatures below 17.5 °C as well above 35.5 °C can be considered as the lethal temperatures already during embryonic period and those below 19 °C and above 33 °C as the lethal ones during larval period, respectively. In term of bioenergy, the thermal optimum for early life history in African catfish lies between 23 - 28 °C.

Made available in DSpace on 2014-06-11T19:32:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-17Bitstream added on 2014-06-13T19:22:04Z : No. of bitstreams: 1 costa_sm_dr_botfca.pdf: 644719 bytes, checksum: e6ca1b81aea205b531d4ed5454c33d82 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho teve como objetivo prolongar a vida útil de ameixas cv. Gulfblaze, provenientes de Holambra II – SP, com o emprego da irradiação gama, embalagem e o uso de condicionamento térmico em frutos refrigerados. Foram realizados dois experimentos: Experimento 1 - frutos irradiados (0,0; 0,4; 0,6; 0,8; 1,0kGy) submetidos à atmosfera modificada passiva e Experimento 2 - frutos submetidos ao condicionamento térmico (10±2°C por 2 dias), irradiados (0,0; 0,4; 0,6; 0,8; 1,0kGy) submetidos à atmosfera modificada passiva. Os frutos foram selecionados e embalados para então serem irradiados no IPEN, localizado em São Paulo – SP. Logo após seguiram para o Laboratório de Frutas e Hortaliças, pertencente ao Departamento de Gestão e Tecnologia Agroindustrial, da Faculdade de Ciências Agronômicas – UNESP – Câmpus de Botucatu, SP. Nos dois experimentos, os frutos após os tratamentos, foram armazenados em B.O.D. a 0±2°C e com 90±5% de UR por 35 dias. As avaliações foram realizadas a cada cinco dias, durante 35 dias de armazenamento. As alterações na qualidade pós-colheita foram detectadas por meio das análises de perda de massa fresca, firmeza, pH, acidez titulável, sólidos solúveis, razão SS/AT “Ratio” açúcares redutores, açúcares totais, vitamina C total, pigmentos, compostos fenólicos totais e taxa de respiração. O delineamento estatístico empregado foi inteiramente casualizado com três repetições por tratamento para cada um dos oito tempos de avaliação, utilizando-se o Teste de Tukey a 5% de probabilidade. Nas condições em que os experimentos foram realizados, os resultados permitem concluir que, os frutos da ameixeira ‘Gulfblaze’ são resistentes à refrigeração (0±2°C), não apresentando sintomas de injúria até os 35 dias de armazenamento. O condicionamento levou a uma aceleração do amadurecimento, mostrando-se não recomendável para essa variedade de ameixas / The present work aims at protracting the lifespan of plums cv. Gulfblaze, originating from Holambra II, São Paulo, by application of gamma irradiation, packaging and the use of thermal conditioning on cold fruits. Two experiments were made: Experiment 1. irradiated fruits (0,0; 0,4; 0,6; 0,8; 1,0KGy) undergo a passive modified atmosphere and Experiment 2. fruits undergo thermal conditioning (10±2°C for 2 days), irradiation (0,0; 0,4; 0,6; 0,8; 1,0KGy), and are subjected to passive modified atmosphere. The fruits were selected and packed, and then irradiated at IPEN, located in São Paulo – SP. Thereupon, they were directed to the Laboratory of Fruit and Vegetables from the Department of Management and Agribusiness Technology of the Agronomic Sciences Faculty - UNESP - Botucatu, Brazil. In both experiments, after the treatment the fruits were stored in B.O.D at 0±2°C with 90±5% RH for 35 days. Evaluations were conducted every five days, for the 35 days of storage. Alterations on post-harvest quality were detected by means of analysis of fresh mass loss, consistency (firmness), pH, total titratable acidity, soluble solids, ‘Ratio’ (SS/TTA), reducing sugar content, total reducing sugar, vitamin C total, pigment, phenolic compounds and respiratory rates. The employed statistical design was thoroughly randomized with three replications per treatment for each of the eight evaluations using the Turkey’s Test to 5% of probability. Under the circumstances in which the experiments were performed, the results allow for the conclusion that ‘Gulfblaze’ plum fruits are resistant to refrigeration (0±2°C), with no symptoms of injury during the 35 days at storage. The conditioning led to ripening acceleration, proving to be not advisable for this sort of plum. The use of gamma radiation did not lead to improvement, regardless of the applied dose

Temperature preference, behavioral tolerance, and physiological tolerances were determined for locally captured, invasive juvenile lionfish at four different acclimation temperatures (13°C, 20°C, 25 °C and 32°C). Temperature preferences and avoidance temperatures were evaluated using an automated shuttlebox system that presents subject-driven temperature stimuli to subjects, who control the temperature with their movement throughout the tank for 12 hours. Subjects are tracked by a computer system, with data output approximately every second. Acute preference was calculated from the archived data as the mean temperature that the fish occupied during the first two hours of dynamic experimentation. Acute preference measurements were used to determine final temperature preferendum and avoidance temperatures were used to determine behavioral tolerance. Critical thermal methodology (CTM) determined the CTmin and CTmax of the lionfish with loss of equilibrium (LOE) as the endpoint. It is assumed that beyond this temperature, the fish would be unable to survive. Temperature was increased or decreased by 0.33°C per minute until the end point was reached. Thermal tolerance polygons provide a visual representation of the lower and upper thermal avoidance temperatures, delineating the thermal range of the species. Their CTmin and CTmax (acclimated to 25°C) were compared experimentally with two other Florida reef fish species (Cephalopholis cruentata and Lutjanus apodus). Acute preferences of juvenile invasive lionfish showed a final preferendum at 28.7 ± 1°C, but with no significant difference between acclimation temperatures. The thermal tolerance polygon of invasive lionfish shows a strong correlation between CTM and acclimation temperature, with the highest CTmax at 39.5°C and the lowest CTmin at 9.5°C. The thermal polygon, preference, and avoidance data describes the thermal niche of the lionfish. Lionfish CTM (24.61°C) is narrower than those of C. cruentata (25.25°C) and L. apodus (26.87°C).

Background: Gene expression regulation is one of the fundamental mechanisms of phenotypic plasticity and is expected to respond to selection in conditions favoring phenotypic response. The observation that many organisms increase their stress tolerance after acclimation to moderate levels of stress is an example of plasticity which has been long hypothesized to be based on adaptive changes in gene expression. We report genome-wide patterns of gene expression in two heat-tolerant and two heat-sensitive parthenogenetic clones of the zooplankton crustacean Daphnia pulex exposed for three generations to either optimal (18°C) or substressful (28°C) temperature. Results: A large number of genes responded to temperature and many demonstrated a significant genotype-byenvironment (GxE) interaction. Among genes with a significant GxE there were approximately equally frequent instances of canalization, i.e. stronger plasticity in heat-sensitive than in heat-tolerant clones, and of enhancement of plasticity along the evolutionary vector toward heat tolerance. The strongest response observed is the across-the-board down-regulation of a variety of genes occurring in heat-tolerant, but not in heat-sensitive clones. This response is particularly obvious among genes involved in core metabolic pathways and those responsible for transcription, translation and DNA repair. Conclusions: The observed down-regulation of metabolism, consistent with previous findings in yeast and Drosophila, may reflect a general compensatory stress response. The associated down-regulation of DNA repair pathways potentially creates a trade-off between short-term benefits of survival at high temperature and long-term costs of accelerated mutation accumulation.

Species distribution models are frequently used in ecology to predict the spatial and temporal occurrence of organisms. Direct interpretation of these models assumes that the relationships between the organisms and their environment are manifestations of causal mechanisms. However, in general, the mechanisms producing these associations have not been experimentally validated, which questions our confidence in their interpretation and application. Temperature is one of the most important factors influencing the fitness and distribution of aquatic organisms, and studying the thermal physiology of aquatic invertebrates could provide a useful approach for validating predictions of the species distribution models. Experimental thermal tolerance studies, which assess the physiological limits to temperature, should be useful in interpreting the causal basis for species distribution model predictions. Critical Thermal Maxima experiments are frequently used to measure the thermal tolerance of ectothermic organisms. They represent the temperature at which organisms exhibit disorganized locomotor activity to the point that they lose their ability to escape conditions that will promptly lead to death. Critical Thermal Maxima experiments could, therefore, provide a useful test of the inferred mechanisms of species distribution models. The objective of my study was to determine if Critical Thermal Maxima experiments are associated with the thermal limits inferred from species distribution models. If the models accurately describe causal relationships between predicted distributions of organisms and environmental temperatures, and if the thermal maxima are associated with the limits to organism fitness, I expected to see a strong correspondence between model-derived and experimentally-derived thermal limits. A strong correspondence between model predictions and experimentally obtained thermal maxima would both validate a physiological interpretation of the species distribution models and justify the use of Critical Thermal Maxima experiments alone in predicting species distributions and responses to climate change.

Understanding how organisms respond to climatic variability and novel conditions is becoming an increasingly important task for ecologists. For ectotherms in the northern hemisphere, the response to cold is of special interest, considering that poleward range expansion events and increasing variability of temperatures during winter are already being observed as consequences of a warming planet. Though direction of change in physiological variables in response to cold is well studied in ectotherms, the extent to which traits can change and the rate at which they can change is not. We compared the extent and rate of change in cold tolerance (CTmin) between two long-term captive populations of the Italian wall lizard (Podarcis siculus) during a lab cold-acclimation treatment. Heat tolerance (CTmax), thermal preference (Tpref), temperature dependent rates of oxygen consumption (SMRO2), and temperature dependent rates of water loss (EWL) were also compared between Italian wall lizards previously introduced to Long Island, NY and San Pedro, CA before and after the lab cold acclimation treatment. Because our study coincided with a cold snap during the spring 2018 season for the San Pedro, CA population, we also studied the effects of cold acclimatization on wild lizards from the CA population. After initial lab acclimation of the lizards to laboratory conditions, SMRO2 at 15°C and EWL at 10°C were higher in NY lizards compared to CA lizards. Lizards from the two populations did not differ in any other variables measured before the cold acclimation treatment. We found that lizards from the NY population experienced an 80% decrease in CTmin following a switch from 20°C:18°C to 17.5°C:16°C (12h light:12h dark) acclimation treatment. Lizards from the CA population did not decrease CTmin in response to the same cold acclimation treatment. Overall, NY lizards decreased CTmin, CTmax, and Tpref following cold acclimation, whereas CA lizards decreased CTmax only. Wild CA lizards decreased CTmax following the cold spring 2018 season in a manner similar to that of lab acclimated NY and CA lizards, suggesting that these lizards do not maintain a high CTmax when the environment is unlikely to expose them to high temperatures. Thermal sensitivity (Q10) of SMRO2 and EWL was lower in NY lizards, suggesting physiological adaptation to fluctuation in diurnal temperatures. The ratio of CO2 produced to O2 consumed (respiratory exchange ratio, RER) measured at 15°C increased in NY lizards following cold acclimation suggesting an increased use of carbohydrates and/or an increased production of lipids in the colder conditions. These responses in combination with the higher observed plasticity in NY lizards are in accordance with the climatic variability hypothesis, which predicts that organisms from more variable climates will be better adapted to physiologically respond to variable conditions. The higher capacity for physiological plasticity may explain the relatively high success of P. siculus in NY and other northern U.S. states. By describing the rate of change of CTmin during cold acclimation we hope to better understand how these lizards minimize the risk of low temperature exposure during winter. We ultimately hope to incorporate the rate at which cold tolerance can change into predictions of species distributions and hypothesis tests investigating the relationship between climatic variability and the rate at which animals can exhibit plasticity.

Understanding the effects of natural variation in environmental temperature on organisms and how those organisms evolve to live in different thermal environments is a central tenet of evolutionary physiology. Phenotypic differences among populations are the result of local adaptation, innate genetic differences between populations, and phenotypic plasticity, differential responses to the environment. Although not mutually exclusive, distinguishing between these paradigms can help illuminate species boundaries resulting from thermal limitations in physiology. For my dissertation, I examined geographic variation in measures of thermal physiology of the western fence lizard, Sceloporus occidentalis to understand the relative role of adaptation and acclimation in determining the thermal biology of populations of this species living in different thermal environments. To achieve this goal I measured three indices of physiological function; body temperature, thermal tolerance and heat shock protein (Hsp70) abundance, across geographic and seasonal variation in temperature. Furthermore, I examined variation in sprint speed performance before and after heat stress and its relationship to Hsp70 to determine if stress protein expression is a reliable indicator of whole organism physiological stress. I found that geographic location can have a major effect on thermal physiology and performance in S. occidentalis in that thermal tolerance, Hsp70, and sprint speed varied with site and season with warmer southern sites typically more heat adapted than cooler northern sites. I also found a trade off in thermal tolerance suggesting that specialization to temperature was occurring in these lizards. Finally, lizards with increased Hsp70 were typically slower after heat stress indicating that Hsp70 is a reliable indicator of organism stress. Despite these findings, there was no difference in body temperature among sites and seasonal patterns in thermal tolerance suggest that during certain times of the year plastic responses to temperature may mask adaptive differences. Here, I argue that temperature differences between sites has resulted in temperature adaptation at these sites, but that plastic responses to seasonal variation in temperature can become more important during certain times of the year. Although these relationships have been thoroughly studied in invertebrate organisms, further research should examine whether these patterns exist in other vertebrate ectotherm species.