| 1. |
- Joyce, W., et al.
(författare)
-
Exploring nature's natural knockouts: in vivo cardiorespiratory performance of Antarctic fishes during acute warming
- 2018
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:15
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Joyce, W., et al.
(författare)
-
The effects of thermal acclimation on cardio-respiratory performance in an Antarctic fish (Notothenia coriiceps)
- 2018
-
Ingår i: Conservation Physiology. - : Oxford University Press (OUP). - 2051-1434. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- The Southern Ocean has experienced stable, cold temperatures for over 10 million years, yet particular regions are currently undergoing rapid warming. To investigate the impacts of warming on cardiovascular oxygen transport, we compared the cardio-respiratory performance in an Antarctic notothenioid (Notothenia coriiceps) that was maintained at 0 or 5 degrees C for 6.0-9.5 weeks. When compared at the fish's respective acclimation temperature, the oxygen consumption rate and cardiac output were significantly higher in 5 degrees C-acclimated than 0 degrees C-acclimated fish. The 2.7-fold elevation in cardiac output in 5 degrees C-acclimated fish (17.4 vs. 6.5 ml min(-1) kg(-1)) was predominantly due to a doubling of stroke volume, likely in response to increased cardiac preload, as measured by higher central venous pressure (0.15 vs. 0.08 kPa); tachycardia was minor (295 vs. 25.2 beats min(-1)). When fish were acutely warmed, oxygen consumption rate increased by similar amounts in 0 degrees C- and 5 degrees C-acclimated fish at equivalent test temperatures. In both acclimation groups, the increases in oxygen consumption rate during acute heating were supported by increased cardiac output achieved by elevating heart rate, while stroke volume changed relatively little. Cardiac output was similar between both acclimation groups until 12 degrees C when cardiac output became significantly higher in 5 degrees C-acclimated fish, driven largely by their higher stroke volume. Although cardiac arrhythmias developed at a similar temperature (similar to 14.5 degrees C) in both acclimation groups, the hearts of 5 degrees C-acclimated fish continued to pump until significantly higher temperatures (CTmax for cardiac function 17.7 vs. 15.0 degrees C for 0 degrees C-acclimated fish). These results demonstrate that N. coriiceps is capable of increasing routine cardiac output during both acute and chronic warming, although the mechanisms are different (heart rate-dependent versus primarily stroke volume-dependent regulation, respectively). Cardiac performance was enhanced at higher temperatures following 5 degrees C acclimation, suggesting cardiovascular function may not constrain the capacity of N. coriiceps to withstand a warming climate.
|
|
