Critical thermal maximum in freshwater fish in Argentina, South America

AbstractAlthough most of the notothenioid fishes have geographic distributions restricted to the Southern Ocean, several species with inferred Antarctic origins have come to permanently inhabit the warmer waters around New Zealand and southern South America. However, it remains unknown whether the Antarctic ancestry of these secondarily temperate species continues to influence their modern heat tolerance. We investigated the heat tolerance of one such secondarily temperate nototheniid, Notothenia angustata, which is now endemic to the waters around the South Island of New Zealand. Their heat tolerance was determined using the critical thermal maximum (CTMax) both when acclimatized to their winter water temperatures (7.9°C), and warm acclimated (15°C) near the summer water temperatures in Otago Harbour. When compared to equivalently acclimated specimens of the basal New Zealand notothenioid Bovichtus variegatus, N. angustata have consistently lower CTMaxs, though they are significantly greater than those determined from 10°C acclimated specimens of its endemic Antarctic congener, N. coriiceps. While this shows greater heat tolerance in the secondarily temperate N. angustata than in endemic Antarctic species, it also suggests that some of its ancestral intolerance to heat persists.

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Critical thermal maximum in mice

Journal of Applied Physiology ◽

10.1152/jappl.1976.40.5.683 ◽

1976 ◽

Vol 40 (5) ◽

pp. 683-687 ◽

Cited By ~ 34

Author(s):

G. L. Wright

Keyword(s):

Heat Stress ◽

Cooling Capacity ◽

Heating Time ◽

Critical Thermal Maximum ◽

Thermal Limit ◽

Ambient Temperatures ◽

Thermal Maximum ◽

Righting Reflex ◽

Colonic Temperature ◽

Extended Exposure

The critical thermal maximum (the colonic temperature of heat-induced convulsion and righting reflex loss) and thermoregulatory response of male mice were examined following I, exposure to colonic temperature (Tco) 42 degrees C; II, a single exposure to the critical thermal maximum (Tco 44 degrees C); AND III, acclimation at ambient temperatures of 15 or 30 degrees C for 14 days. The critical thermal maximum (CTM) was greater in 30 degrees C acclimated mice than 15 degrees C acclimated mice but was unchanged in mice surviving exposure to Tco 42 degrees C or the CTM. The heating time to apparent breakdown of thermoregulation coincident with an explosive rise in the Tco during exposure to ambient temperature 40.8 degrees C was increased (100%) during the 48-h period following exposure to Tco 42 degrees. It appeared that mice exposed to severe, short-term heat stress (Tco 42 degrees) undergo a compensatory increase in their thermoregulatory cooling capacity with little or no change in the upper temperature tolerated. The animals did, however, exhibit the capability for adaptive adjustments of the upper thermal limit during extended exposure to the more prolonged and less severe environmental heat stress of acclimation at 30 degrees C.

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Water temperature affects aggressive interactions in a Neotropical cichlid fish

Neotropical Ichthyology ◽

10.1590/1982-0224-20170081 ◽

2018 ◽

Vol 16 (1) ◽

Cited By ~ 7

Author(s):

Manuela L. Brandão ◽

Gisele Colognesi ◽

Marcela C. Bolognesi ◽

Roselene S. Costa-Ferreira ◽

Thaís B. Carvalho ◽

...

Keyword(s):

Aggressive Behavior ◽

Water Temperature ◽

Elevated Temperatures ◽

Cichlid Fish ◽

Aquatic Organisms ◽

Swimming Activity ◽

Critical Thermal Maximum ◽

Physiological Mechanisms ◽

Aggressive Interactions ◽

Thermal Maximum

ABSTRACT Changes in water temperature may affect the aggressive behavior of aquatic organisms, such as fish, either by changing some physiological mechanisms or by increasing the probability of encounters between individuals as a result of variation in their swimming activity. In our study, we evaluated the influence of increasing and decreasing temperature on the aggressive behavior of the Neotropical cichlid fish Cichlasoma paranaense. Firstly, we tested the critical thermal maximum (CTMax) tolerated by this species. Then, we tested the effect of decreasing or increasing the water temperature in 6o C (starting at 27° C) on the aggressive interactions of fish under isolation or housed in groups. We found a CTMax value of 39° C for C. paranaense. We also observe that a 6° C decrease in water temperature lowers swimming activity and aggressive interactions in both isolated and group-housed fish, as expected. On the other hand, the increase in temperature had no effect on the fish’s aggressive behavior, neither for isolated nor for grouped fish. We concluded that C. paranaense shows high tolerance to elevated temperatures and, in turn, it does not affect aggressive behavior. Nevertheless, we cannot dismiss possible effects of elevated temperatures on aggressive interactions over longer periods.

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