Critical thermal maximum (CT_max) and hematology of shortnose sturgeons (Acipenser brevirostrum) acclimated to three temperatures

Abstract

Quantifying a species thermal tolerance is critical to assessing biological impacts of anticipated increases in temperature (e.g., climate change). Although many studies have documented the critical thermal maximum (CT max ) of fish, there is a paucity of research on thermal biology of sturgeon. The shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818) is a threatened species that exists along the eastern coast of North America. They can be exposed to temperatures ranging from freezing to above 25°C. Using a heating rate of 6°C/h, CT max and the associated hematological responses of shortnose sturgeon acclimated to 10, 15, and 20°C were determined. There was a significant positive relationship between CT max and body mass, and CT max increased significantly with increases in acclimation temperature (T a ). In general, hematology of thermally stressed fish was modified relative to control (nonstressed) fish. Hematocrit, plasma lactate, and plasma Na + and Cl -of fish were all significantly influenced by thermal stress and T a . Glucose and K + were only significantly influenced by thermal stress. Future studies should address the importance of other stressors, such as salinity and toxicants, on thermal relationships of sturgeon.Résumé : La quantification de la tolérance thermique d'une espèce est essentielle à l'évaluation des impacts biologiques des augmentations anticipées de température (p. ex. changement climatique). Si de nombreuses études ont documenté le maximum thermique critique (CT max ) de poissons, peu de travaux se sont penchés sur la thermobiologie des esturgeons. L'esturgeon à museau court (Acipenser brevirostrum LeSueur, 1818) est une espèce menacée présente le long de la côte est de l'Amérique du Nord. Ces poissons peuvent être exposés à des températures allant du point de congélation à plus de 25°C. En appliquant un taux de réchauffement de 6°C/h, le CT max et les réactions hématologiques associées d'esturgeons à museau court acclimatés à des températures de 10, 15 et 20°C ont été déterminés. Une relation positive significative en est ressortie entre le CT max et la masse corporelle, et le CT max augmentait de manière significative à mesure qu'augmentait la température d'acclimatation. En général, l'hématologie des poissons assujettis à un stress thermique divergeait de celle de poissons témoins (non assujettis à un stress). Le stress thermique et la température d'acclimatation (T a ) avaient une incidence significative sur l'hématocrite, ainsi que sur les concentrations de lactate et de Na + et Cl -du plasma des poissons, alors que seul le stress thermique exerçait une influence significative sur le glucose et le K + . Les études futures devraient se pencher sur l'importance d'autres facteurs de stress, comme la salinité et les substances toxiques, dans les relations thermiques des esturgeons. [Traduit par la Rédaction] Mots-clés : Acipenser brevirostrum, maximum thermique critique, température d'acclimatation, taille corporelle, hématologie, esturgeon à museau court.

Critical thermal maxima and hematology for juvenile Atlantic (Acipenser oxyrinchusMitchill 1815) and shortnose (Acipenser brevirostrumLesueur, 1818) sturgeons

“…This is perplexing since most sturgeon species are protected under legislation due to human‐made disturbances that might involve water temperature alterations (Pikitch et al., ). The critical thermal maximum values for Atlantic and shortnose sturgeon noted in the present study were found to be similar to those in other studies using pallid ( Scaphirhynchus albus ), Lake ( Acipenser fulvescens ), shortnose, shovelnose ( Scaphirhynchus platorynchus ) and green ( Acipenser medirostris ) sturgeons (Sardella et al., ; Zhang and Kieffer, ; D. Deslauriers, unpubl. data; Table ).…”

“…CTmax led to a marked change in a number of blood parameters across sturgeon species, which is indicative of increased stress in the animal (Wedemeyer et al., ; Barton et al., ). Lactate concentrations increased in Atlantic and shortnose sturgeon during the thermal stress and at levels comparable to previous research on shortnose sturgeon (Zhang and Kieffer, ; Y. Zhang and J. D. Kieffer, unpubl. data).…”

Physiological evaluation of the behavior and epidermis of freshwater planarians (Girardia tigrina and Girardia sp.) exposed to stressors

“…The adoption of the CTM parameter allowed researchers to evaluate the thermal tolerance of different organisms (Cowles and Bogert, 1944; Lutterschmidt and Hutchison, 1997; Zhang and Kieffer, 2014). Limnic planarians exposed to the CTM, show signs of contortions, sluggishness, and an injured epidermis, losing their ability to move properly before dying (Claussen and Walters, 1982; Tsukuda and Ogoshi, 1985).…”

Limited variability in upper thermal tolerance among pure and hybrid populations of a cold-water fish

“…In nature, a loss of equilibrium affects an organism's ability to forage or avoid predation, which may ultimately affect individual fitness. As acclimation temperature ( T a ) has been found to be correlated positively with CT max (Cox et al ., 1974; Zhang and Kieffer, 2014; McDonnell and Chapman, 2015, although see Galbreath et al ., 2004; Recsetar et al ., 2012), the ancestral history and origin of a population are thought to be linked to an organism's ability to tolerate temperature increases (Stockwell et al ., 2003; McDermid et al ., 2012) and, as such, stream temperature regimes may result in population-specific thermal tolerance. A relatively new metric to assess thermal tolerance, agitation temperature, described by McDonnell and Chapman (2015) as the temperature at which a fish first begins to exhibit refugia-seeking behaviour (circling of the chamber, seeking refuge in substrate), may also provide insight to how quickly individuals can sense and attempt to react to environmental change.…”