Search

We designed two environmentally relevant thermal cycling regimes using monitoring data from an Atlantic salmon (Salmo salar) river to determine whether exposure to prior diel cycles stimulated protective mechanisms (e.g., heat hardening) and (or) resulted in physiological and cellular stress. Wild fish were exposed to 3 days of diel cycling in the lab and then exposed to an acute thermal challenge near their upper reported critical temperature. We measured routine metabolic rate across the time course as well as indicators of physiological status (e.g., plasma glucose and osmolality) and cellular stress (e.g., heat shock protein 70). We observed that thermal cycling altered physiological and cellular responses, compared with an acute heat shock, but saw no differences between cycling regimes. Unique temperature regime and tissue-specific responses were observed in heat shock protein induction, metabolites, haematology, and osmotic indicators. Routine metabolic rate was not affected by the thermal cycling and increased according to [Q.sub.10] predictions. While we report unique physiological and cellular responses among all treatment groups, we did not observe a clear indication of a heat hardening response. Nous avons concu deux regimes de cycle thermique de pertinence environnementale reposant sur des donnees de surveillance pour une riviere a saumons de l'Atlantique (Salmo salar) afin de determiner si l'exposition a des cycles nycthemeraux anterieurs stimulait des mecanismes de protection (p. ex. augmentation de la resistance fi la chaleur) et (ou) produisait un stress physiologique ou cellulaire. Des poissons sauvages ont ete exposes a trois jours d'un cycle nycthemeral en laboratoire, puis a un defi thermique aigu approchant leur temperature critique superieure signalee. Nous avons mesure le metabolisme normal dans le temps, ainsi que des indicateurs de l'etat physiologique (p. ex. glucose plasmique et osmolalite) et de stress cellulaire (p. ex. proteine de choc thermique 70). Nous avons observe que les cycles thermiques modifiaient les reactions physiologiques et cellulaires par rapport a un choc thermique aigu, mais n'avons note aucune difference entre les differents cycles thermiques. L'induction de la proteine de choc thermique, les metabolites et les indicateurs hematologiques et osmotiques ont revele des reactions differentes selon le regime thermique et le tissu. Le metabolisme normal n'etait pas influence par le cycle thermique et augmentait conformement aux predictions du [Q.sub.10]. Si nous faisons etat de reactions physiologiques et cellulaires differentes pour tous les groupes traites, nous n'avons observe aucun indice clair d'augmentation de la resistance a la chaleur. [Traduit par la Redaction], Introduction The temperature in natural ecosystems is rarely constant; realworld scenarios involve varying magnitudes of diel temperature fluctuation, coupled with sporadic extreme events (Ma et al. 2015). The dynamic nature [...]

Gas exchange in animals is ultimately diffusion based, generally occurring across dedicated respiratory organs. In many aquatic amphibians, however, multiple modes of gas exchange exist, allowing for the partitioning of O[subscript 2] uptake and CO[subscript 2] excretion between respiratory organs with different efficiencies. For example, due to the physical properties of O[subscript 2] being vastly different between air and water phases, the lung and skin play disproportionately important roles in O[subscript 2] uptake. Many aquatic frogs are renowned for their cutaneous gas exchange capacity, where often the majority of CO[subscript 2] is excreted across the skin. Furthermore, the roles of these gas exchange organs change with the animal's behavior. Under diving conditions, most of the frog's gas exchange needs must be met by the skin. In this article, we describe an interactive undergraduate laboratory that allows a class of students to share equipment while assessing pulmonary and cutaneous respiration in frogs provided with an air/water choice and under enforced dive conditions. Concepts explored in this laboratory exercise include animal energetics, diving reflex, pulmonary and cutaneous gas exchange processes, diffusion-based gas flux, and O[subscript 2] debt. (Contains 2 tables and 4 figures.)

We conclude that the heat shock response is enhanced in juvenile compared with adult rainbow trout, Oncorhynchus mykiss. We have shown that the magnitude of the inducible heat shock response, as measured by increases in the heat shock protein (Hsp) Hsp70 is significantly greater in the hearts of fingerling than in adult trout following an acute (1 h) heat stress at 25[degrees]C. Juvenile fish also express higher levels of constitutive Hsps (Hsc70, Hsp90) in their tissues, possibly reflecting higher rates of protein synthesis and increased chaperone function in this early life stage. This robust heat shock response in juvenile trout may contribute to a greater thermal resistance that is often observed in young salmonid fish. Nous concluons que la reaction au choc thermique est plus importante chez les truites arc-en-ciel, Oncorhynchus mykiss, juveniles que chez les adultes. Nous avons montre que l'intensite de la reaction induite par le choc thermique, mesuree par l'augmentation de la proteine du choc thermique (Hsp) Hsp70, est significativement plus elevee dans le ceur des fretins que dans celui des truites adultes suivant un stress thermique aigu (1 h) a 25[degrees]C. Les jeunes poissons ont aussi une expression de concentrations plus elevees d'Hsp constitutives (Hsc70, Hsp90) dans leurs tissus, ce qui reflete probablement des taux de synthese de proteines plus eleves et une fonction de chaperon plus importante a ce stage precoce de leur cycle biologique. Cette reaction robuste au choc thermique chez les jeunes truites peut contribuer a la resistance thermique plus elevee que l'on observe souvent chez les jeunes salmonides. [Traduit par la Redaction], Introduction Stream temperature is an important factor determining the abundance and distribution of cold-water fish species (de la Hoz Franco and Budy 2005). Although salmonid fish, like rainbow trout (Oncorhynchus [...]

The mechanisms involved in the enhancement of the heat-induced induction of heat-shock proteins (Hsps) by the [beta]-andregenic stimulation in fishes are explained. The stimulation is shown to highly enhance the physiological regulation of the cellular stress response in fishes as well.

Abstract: Endocrine-disrupting chemicals pose a serious threat to the health of animals, particularly those in aquatic ecosystems. One such chemical, the alkylphenolic compound 4-nonylphenol (4-NP), is used extensively as a [...]

The relationship between bioenergetic stress and heat shock protein gene expression was investigated in the nucleated red blood cells of the rainbow trout, Oncorhynchus mykiss. The goal was to elucidate the physiological and biochemical signals that generate stress protein synthesis. It was found that heat shock amounting to 25 degrees Celsius had no significant effect on adenosine triphosphate levels, but induced an increase in HSP70 mRNA. Results also show that a decrease in the cellular energy status does not generate stress protein gene transcription in red blood cells of the rainbow trout and may even restrict induction during extreme metabolic inhibition.

Typically, laboratory studies on the physiological effects of temperature are conducted using stable acclimation temperatures. Nonetheless, information extrapolated from these studies may not accurately represent wild populations living in thermally variable environments. The aim of this study was to compare the growth rate, metabolism and swimming performance of wild Atlantic salmon exposed to cycling temperatures, 16–21°C, and stable acclimation temperatures, 16, 18.5, 21°C. Growth rate, metabolic rate, swimming performance and anaerobic metabolites did not change among acclimation groups, suggesting that within Atlantic salmon's thermal optimum range, temperature variation has no effect on these physiological properties. [ABSTRACT FROM AUTHOR]