Cardiac remodelling in rainbow trout Oncorhynchus mykiss Walbaum in response to phenylhydrazine-induced anaemia

To address how the capacity for oxygen transport influences tolerance of acute warming in fishes, we investigated whether a reduction in haematocrit, by means of intra-peritoneal injection of the haemolytic agent phenylhydrazine, lowered the upper critical temperature of sea bass. A reduction in haematocrit from 42±2% to 20±3% (mean ± s.e.m.) caused a significant but minor reduction in upper critical temperature, from 35.8±0.1 to 35.1±0.2°C, with no correlation between individual values for haematocrit and upper thermal limit. Anaemia did not influence the rise in oxygen uptake between 25 and 33°C, because the anaemic fish were able to compensate for reduced blood oxygen carrying capacity with a significant increase in cardiac output. Therefore, in sea bass the upper critical temperature, at which they lost equilibrium, was not determined by an inability of the cardio-respiratory system to meet the thermal acceleration of metabolic demands.

Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 88%

Anaemia only causes a small reduction in the upper critical temperature of sea bass: is oxygen delivery the limiting factor for tolerance of acute warming in fishes?

Wang

Lefevre

Iversen

et al. 2014

“…Furthermore, changes detected in blood-oxygen carrying capacity may have played a role in modulating f Hmax and T HRmax with acclimation. A previous study on rainbow trout showed a strong relationship with anemia and cardiac workload and cardiac remodeling in an acclimation-temperature-dependent manner (Simonot and Farrell, 2007). This suggests the potential for alterations in cardiac parameters and cardiac workload in G. mirabilis with changes in blood-oxygen carrying capacity.…”

Section: Insights Into the Process Of Acclimationmentioning

confidence: 82%

Physiological plasticity of cardiorespiratory function in a eurythermal marine teleost, the longjaw mudsucker,Gillichthys mirabilis

Jayasundara

Somero

2013

SUMMARYAn insufficient supply of oxygen under thermal stress is thought to define thermal optima and tolerance limits in teleost fish. When under thermal stress, cardiac function plays a crucial role in sustaining adequate oxygen supply for respiring tissues. Thus, adaptive phenotypic plasticity of cardiac performance may be critical for modifying thermal limits during temperature acclimation. Here we investigated effects of temperature acclimation on oxygen consumption, cardiac function and blood oxygen carrying capacity of a eurythermal goby fish, Gillichthys mirabilis, acclimated to 9, 19 and 26°C for 4weeks. Acclimation did not alter resting metabolic rates or heart rates; no compensation of rates was observed at acclimation temperatures. However, under an acute heat ramp, warm-acclimated fish exhibited greater heat tolerance (CT max =33.3, 37.1 and 38.9°C for 9°C-, 19°C-and 26°C-acclimated fish, respectively) and higher cardiac arrhythmia temperatures compared with 9°C-acclimated fish. Heart rates measured under an acute heat stress every week during 28days of acclimation suggested that both maximum heart rates and temperature at onset of maximum heart rates changed over time with acclimation. Hemoglobin levels increased with acclimation temperature, from 35gl −1 in 9°C-acclimated fish to 60-80gl −1 in 19°C-and 26°C-acclimated fish. Oxygen consumption rates during recovery from acute heat stress showed post-stress elevation in 26°C-acclimated fish. These data, coupled with elevated resting metabolic rates and heart rates at warm temperatures, suggest a high energetic cost associated with warm acclimation in G. mirabilis. Furthermore, acclimatory capacity appears to be optimized at 19°C, a temperature shown by behavioral studies to be close to the speciesʼ preferred temperature. Supplementary material available online at

“…While haemoglobin concentration is the primary determinant of blood oxygen carrying capacity (Gallaugher and Farrell, 1998), the present study revealed that a ∼43% decrease in haemoglobin concentration did not significantly affect metabolic attributes (SMR, MMR or AS) when compared with control fish. Previous studies on anaemic fish, with anaemia induced by experimental bleeding or intra-peritoneal injection of the haemolytic agent phenylhydrazine, have shown that they can greatly compensate for a reduced blood oxygen carrying capacity by increasing cardiac output and tissue oxygen extraction to maintain overall oxygen transport (Cameron and Davis, 1970;Simonot and Farrell, 2007). Indeed, ṀO 2 of anaemic fish during thermal ramping increased in a similar exponential manner to that in control fish and no significant differences in ṀO 2 were observed between the groups throughout the entire thermal ramping experiment.…”

Section: Reduced Blood Oxygen Carrying Capacity Does Not Affect Acutementioning

confidence: 99%

Experimental manipulations of tissue oxygen supply do not affect warming tolerance of European perch

Brijs

Jutfelt

Clark

et al. 2015

A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally induced anaemia) in European perch (Perca fluviatilis Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CT max ). Hyperoxia resulted in a twofold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CT max in comparison with control fish (34.6± 0.1 versus 34.0±0.5°C, respectively). Anaemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope or CT max (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anaemic perch during thermal ramping increased in a similar exponential manner to that in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CT max of fishes.