Postprandial metabolism of Pacific bluefin tuna ( Thunnus orientalis )

752

870

SummaryMeasurements of aerobic scope [the difference between minimum and maximum oxygen consumption rate (M O2,min and M O2,max , respectively)] are increasing in prevalence as a tool to address questions relating to fish ecology and the effects of climate change. However, there are underlying issues regarding the array of methods used to measure aerobic scope across studies and species. In an attempt to enhance quality control before the diversity of issues becomes too great to remedy, this paper outlines common techniques and pitfalls associated with measurements of M O2,min , M O2,max and aerobic scope across species and under different experimental conditions. Additionally, we provide a brief critique of the oxygen-and capacity-limited thermal tolerance (OCLTT) hypothesis, a concept that is intricately dependent on aerobic scope measurements and is spreading wildly throughout the literature despite little evidence for its general applicability. It is the intention of this paper to encourage transparency and accuracy in future studies that measure the aerobic metabolism of fishes, and to highlight the fundamental issues with assuming broad relevance of the OCLTT hypothesis.

Section: Minimum Oxygen Consumption Ratementioning

confidence: 99%

Aerobic scope measurements of fishes in an era of climate change: respirometry, relevance and recommendations

Clark

Sandblom

Jutfelt

2013

752

870

“…Bluefin tuna display the highest level of endothermy among teleost fishes, using metabolic heat to maintain their body temperature above the ambient water temperature (Carey and Gibson, 1983;Block et al, 2001;Walli et al, 2009). They also exhibit a high metabolic capacity and rates of digestion relative to other fishes (Brill, 1996;Blank et al, 2007;Clark et al, 2010). Bluefin tuna experience a wide range of ambient temperatures in the ocean and are often exposed to large changes in ambient temperature (~10°C) through their horizontal and vertical movements (Gunn and Block, 2001;Walli et al, 2009;Kitagawa et al, 2007b;Boustany et al, 2010;Lawson et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The well-observed postprandial increase in metabolism is also termed the heat increment of feeding (HIF) or diet-induced thermogenesis (DIT). In bluefin tuna, metabolic rate and visceral temperature have both been found to increase on ingestion of a meal (Carey et al, 1984;Fitzgibbon and Seymour, 2009;Clark et al, 2010). Direct measurements of oxygen consumption rates in a flume have shown that postprandial changes in visceral temperature closely track changes in metabolic rate, with a small lag (Clark et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In bluefin tuna, visceral heat is retained by extensive vascular counter-current heat-exchangers (hepatic retia mirabilia) in the circulatory pathway to key organs involved in digestion (Carey et al, 1984). The lag in the visceral temperature increase may be a result of thermal inertia, but could alternatively be caused by active regulation of the blood flow through the heat exchanger to minimize convective heat loss (Clark et al, 2010). Untangling this process is complicated by the placement of implanted tags, and the fact that multiple organs contribute to heat generation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quantifying energy intake in Pacific bluefin tuna (Thunnus orientalis) using the heat increment of feeding

Whitlock

Walli

Cermeño

et al. 2013

Self Cite

SUMMARYUsing implanted archival tags, we examined the effects of meal caloric value, food type (sardine or squid) and ambient temperature on the magnitude and duration of the heat increment of feeding in three captive juvenile Pacific bluefin tuna. The objective of our study was to develop a model that can be used to estimate energy intake in wild fish of similar body mass. Both the magnitude and duration of the heat increment of feeding (measured by visceral warming) showed a strong positive correlation with the caloric value of the ingested meal. Controlling for meal caloric value, the extent of visceral warming was significantly greater at lower ambient temperature. The extent of visceral warming was also significantly higher for squid meals compared with sardine meals. By using a hierarchical Bayesian model to analyze our data and treating individuals as random effects, we demonstrate how increases in visceral temperature can be used to estimate the energy intake of wild Pacific bluefin tuna of similar body mass to the individuals used in our study. Supplementary material available online at

“…To our knowledge there is no study describing the transcriptional changes during and following a postprandial period in fish, with most studies focusing on the changes in metabolic rate (Clark et al, 2010;Vanella et al, 2010) and the plasma level of metabolites following feeding (Eames et al, 2010;Eliason et al, 2010;Wood et al, 2010). We have investigated transcriptional regulation in the fast myotomal muscle of male zebrafish in response to a single satiating meal delivered at first light.…”

Section: Introductionmentioning

confidence: 99%

Insulin-like growth factor (IGF) signalling and genome-wide transcriptional regulation in fast muscle of zebrafish following a single-satiating meal

Amaral

Johnston

2011

SUMMARY Male zebrafish (Danio rerio) were fasted for 7 days and fed to satiation over 3 h to investigate the transcriptional responses to a single meal. The intestinal content at satiety (6.3% body mass) decreased by 50% at 3 h and 95% at 9 h following food withdrawal. Phosphorylation of the insulin-like growth factor (IGF) signalling protein Akt peaked within 3 h of feeding and was highly correlated with gut fullness. Retained paralogues of IGF hormones genes were regulated with feeding, with igf1a showing a pronounced peak in expression after 3 h and igf2b after 6 h. Igf-I receptor transcripts were markedly elevated with fasting, and decreased to their lowest levels 45 min after feeding. igf1rb transcripts increased more quickly than igf1ra transcripts as the gut emptied. Paralogues of the insulin-like growth factor binding proteins (IGFBPs) were constitutively expressed, except for igfbp1a and igfbp1b transcripts, which were significantly elevated with fasting. Genome-wide transcriptional responses were analysed using the Agilent 44K oligonucleotide microarray and selected genes validated by qPCR. Fasting was associated with the upregulation of genes for the ubiquitin-proteasome degradation pathway, anti-proliferative and pro-apoptotic genes. Protein chaperones (unc45b, hspd1, hspa5, hsp90a.1, hsp90a.2) and chaperone interacting proteins (ahsa1 and stip1) were upregulated 3 h after feeding along with genes for the initiation of protein synthesis and mRNA processing. Transcripts for the enzyme ornithine decarboxylase 1 showed the largest increase with feeding (11.5-fold) and were positively correlated with gut fullness. This study demonstrates the fast nature of the transcriptional responses to a meal and provides evidence for differential regulation of retained paralogues of IGF signalling pathway genes.