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Exploring nature's natural knockouts: in vivo cardiorespiratory performance of Antarctic fishes during acute warming

Journal article
Authors W. Joyce
S. Egginton
A. P. Farrell
E. L. Crockett
K. M. O'Brien
Michael Axelsson
Published in Journal of Experimental Biology
Volume 221
Issue 15
ISSN 0022-0949
Publication year 2018
Published at Department of Biological and Environmental Sciences
Language en
Links dx.doi.org/10.1242/jeb.183160
Keywords Cardiac output, Heart rate, Stroke volume, ECG, Warming, Sympathovagal balance, hemoglobin-free fish, chaenocephalus-aceratus, pagothenia-borchgrevinki, notothenioid fishes, sockeye-salmon, rainbow-trout, cardiac-performance, thermal tolerance, oxygen-transport, climate-change, Life Sciences & Biomedicine - Other Topics
Subject categories Environmental Sciences

Abstract

We tested the hypothesis that blackfin icefish (Chaenocephalus aceratus), one of the six species in the family Channichthyidae (the icefishes) that do not express haemoglobin and myoglobin, lack regulatory cardiovascular flexibility during acute warming and activity. The experimental protocols were designed to optimize the surgical protocol and minimize stress. First, minimally invasive heart rate (f(H)) measurements were made during a thermal ramp until cardiac failure in C. aceratus and compared with those from the closely related red-blooded black rockcod (Notothenia coriiceps). Then, integrative cardiovascular adjustments were more extensively studied using flow probes and intravascular catheters in C. aceratus during acute warming (from 0 to 8 degrees C) at rest and after imposed activity. Chaenocephalus aceratus had a lower routine f H than N. coriiceps (9 beats min(-1) versus 14 beats min(-1)) and a lower peak f(H )during acute warming (38 beats min' versus 55 beats min(-1)) with a similar cardiac breakpoint temperature (13 and 14 degrees C, respectively). Routine cardiac output ((Q) over dot) for C. aceratus at similar to 0 degrees C was much lower (26.6 ml min(-1) kg(-1)) than previously reported, probably because fish in the present study had a low f(H) (12 beats min(-1)) indicative of a high routine vagal tone and low stress. Chaenocephalus aceratus increased oxygen consumption during acute warming and with activity. Correspondingly, (Q) over dot increased considerably (maximally 86.3 ml min(-1) kg(-1)), as did vascular conductance (5-fold). Thus, unlike earlier suggestions, these data provide convincing evidence that icefish can mount a well-developed cardiovascular regulation of heart rate, cardiac output and vascular conductance, and this regulatory capacity provides flexibility during acute warming.

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