Calibration of a hand‐held haemoglobin analyser for use on fish blood

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.

Section: Ct Max Protocolmentioning

confidence: 99%

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

Brijs

Jutfelt

Clark

et al. 2015

“…Blood haemoglobin (Hb) concentration was determined using a Hemocue Hb 201+ unit (Hemocue ® AB, Ängelholm, Sweden) with values corrected for salmonid fish blood according to Clark et al (2008).…”

Section: Acquisition Of Cardiovascular Variables and Analytical Procementioning

confidence: 99%

Bigger is not better: cortisol-induced cardiac growth and dysfunction in salmonids

Johansen

Sandblom

Skov

et al. 2017

Stress and elevated cortisol levels are associated with pathological heart growth and cardiovascular disease in humans and other mammals. We recently established a link between heritable variation in post-stress cortisol production and cardiac growth in salmonid fish too. A conserved stimulatory effect of the otherwise catabolic steroid hormone cortisol is probably implied, but has to date not been established experimentally. Furthermore, whereas cardiac growth is associated with failure of the mammalian heart, pathological cardiac hypertrophy has not previously been described in fish. Here, we show that rainbow trout (Oncorhynchus mykiss) treated with cortisol in the diet for 45 days have enlarged hearts with lower maximum stroke volume and cardiac output. In accordance with impaired cardiac performance, overall circulatory oxygen-transporting capacity was diminished as indicated by reduced aerobic swimming performance. In contrast to the well-known adaptive/physiological heart growth observed in fish, cortisol-induced growth is maladaptive. Furthermore, the observed heart growth was associated with up-regulated signature genes of mammalian cardiac pathology, suggesting that signalling pathways mediating cortisol-induced cardiac remodelling in fish are conserved from fish to mammals. Altogether, we show that excessive cortisol can induce pathological cardiac remodelling. This is the first study to report and integrate the etiology, physiology and molecular biology of cortisol-induced pathological remodelling in fish.

“…Haematocrit (Hct) of blood samples was determined using microcapillary tubes spun at 10,000g for 7min, haemoglobin concentration ([Hb]) was determined using a handheld haemoglobin analyser calibrated for fish blood (HemoCue 201+) (Clark et al, 2008a), and mean cell haemoglobin concentration (MCHC) was calculated as [Hb]/(Hct/100).…”

Section: Data Analyses and Statisticsmentioning

confidence: 99%

Exceptional aerobic scope and cardiovascular performance of pink salmon (Oncorhynchus gorbuscha) may underlie resilience in a warming climate

Clark

Jeffries

Hinch

et al. 2011

170

173

SUMMARYLittle is known of the physiological mechanisms underlying the effects of climate change on animals, yet it is clear that some species appear more resilient than others. As pink salmon (Oncorhynchus gorbuscha) in British Columbia, Canada, have flourished in the current era of climate warming in contrast to other Pacific salmonids in the same watershed, this study investigated whether the continuing success of pink salmon may be linked with exceptional cardiorespiratory adaptations and thermal tolerance of adult fish during their spawning migration. Sex-specific differences existed in minimum and maximum oxygen consumption rates (M O2,min and M O2,max , respectively) across the temperature range of 8 to 28°C, reflected in a higher aerobic scope (M O2,max -M O2,min ) for males. Nevertheless, the aerobic scope of both sexes was optimal at 21°C (T opt ) and was elevated across the entire temperature range in comparison with other Pacific salmonids. As T opt for aerobic scope of this pink salmon population is higher than in other Pacific salmonids, and historic river temperature data reveal that this population rarely encounters temperatures exceeding T opt , these findings offer a physiological explanation for the continuing success of this species throughout the current climate-warming period. Despite this, declining cardiac output was evident above 17°C, and maximum attainable swimming speed was impaired above ~23°C, suggesting negative implications under prolonged thermal exposure. While forecasted summer river temperatures over the next century are likely to negatively impact all Pacific salmonids, we suggest that the cardiorespiratory capacity of pink salmon may confer a selective advantage over other species.