William Davison

The Effects of Exercise Training on Teleost Fish, a Review of Recent Literature

Abstract Recent literature on the effects of training on teleost fish has been reviewed. There has been a good deal of recent work on species of fish other than salmonids, thus increasing knowledge of species not noted for their athletic abilities. Training at speeds of 1.5 bl s −1 or less improves growth rate and food conversion efficiencies in many species. It increases aerobic potentials in red and white muscles and improves heart performance. Oxygen-carrying capacity of the blood is increased, allowing more blood to be directed towards the gut. Sprint training is highly stressful.

A falsification of the thermal specialization paradigm: compensation for elevated temperatures in Antarctic fishes.

Specialization to a particular environment is one of the main factors used to explain species distributions. Antarctic fishes are often cited as a classic example to illustrate the specialization process and are regarded as the archetypal stenotherms. Here we show that the Antarctic fish Pagothenia borchgrevinki has retained the capacity to compensate for chronic temperature change. By displaying astounding plasticity in cardiovascular response and metabolic control, the fishes maintained locomotory performance at elevated temperatures. Our falsification of the specialization paradigm indicates that the effect of climate change on species distribution and extinction may be overestimated by current models of global warming.

Antarctic fish can compensate for rising temperatures: Thermal acclimation of cardiac performance in Pagothenia borchgrevinki

SUMMARY Antarctic fish Pagothenia borchgrevinki in McMurdo Sound, Antarctica, inhabit one of the coldest and most thermally stable of all environments. Sea temperatures under the sea ice in this region remain a fairly constant –1.86°C year round. This study examined the thermal plasticity of cardiac function in P. borchgrevinki to determine whether specialisation to stable low temperatures has led to the loss of the ability to acclimate physiological function. Fish were acclimated to– 1°C and 4°C for 4–5 weeks and cardiac output was measured at rest and after exhaustive exercise in fish acutely transferred from their acclimation temperature to –1, 2, 4, 6 and 8°C. In the– 1°C acclimated fish, the factorial scope for cardiac output was greatest at –1°C and decreased with increasing temperature. Increases in cardiac output with exercise in the –1°C acclimated fish was achieved by increases in both heart rate and stroke volume. With acclimation to 4°C, resting cardiac output was thermally independent across the test temperatures; furthermore, factorial scope for cardiac output was maintained at 4, 6 and 8°C, demonstrating thermal compensation of cardiac function at the higher temperatures. This was at the expense of cardiac function at –1°C, where there was a significant decrease in factorial scope for cardiac output in the 4°C acclimated fish. Increases in cardiac output with exercise in the 4°C acclimated fish at the higher temperatures was achieved by changes in heart rate alone, with stroke volume not varying between rest and exercise. The thermal compensation of cardiac function in P. borchgrevinki at higher temperatures was the result of a change in pumping strategy from a mixed inotropic/chronotropic modulated heart in –1°C acclimated fish at low temperatures to a purely chronotropic modulated heart in the 4°C acclimated fish at higher temperatures. In spite of living in a highly stenothermal cold environment, P. borchgrevinki demonstrated the capacity to thermally acclimate cardiac function to elevated temperatures, thereby allowing the maintenance of factorial scope and the support of aerobic swimming at higher temperatures.

Training and its effects on teleost fish

Abstract 1. 1. The effects of training on teleost fish have been reviewed. 2. 2. Most studies have concentrated on low speed exercise and there is a lack of work on the effects of sprint training. 3. 3. Generally, training affects fish in similar ways to those changes seen in mammals, although fish are much less plastic.

The aerobic scope of an antarctic fish, Pagothenia borchgrevinki and its significance for metabolic cold adaptation

SummaryResting weight-specific oxygen consumption of the cryopelagic Antarctic nototheniid Pagothenia borchgrevinki at 0°C was 39.6 ml kg-1 · h-1 for a 50 g fish, with oxygen consumption being described by the regression equation: log10 VO2(ml/h)=−1.104+0.825 log10 Mb (g). These values are considerably below those raported by Wohlschlag (1964a,b). VO2 max. in forced swimming was described by the regression equation: log10 VO2 max = −0.507+0.823 log10 Mb. Despite low basal metabolism, factorial aerobic scope is similar to that reported for most other teleost fish, as is the cost of net transport. Myotomal muscles were used only at the highest swimming speeds and once they were recruited the fish fatigued rapidly. After swimming, oxygen debt was repaid rapidly, with a half-time of 20 min.

Recovery from exhausting exercise in an Antarctic fish, Pagothenia borchgrevinki

SummaryPagothenia borchgrevinki, an Antarctic teleost fish was swum to exhaustion and changes in lactic acid levels and blood haematocrit were monitored during recovery. The fish did not perform well at high swimming speeds due to an inability of the white myotomal muscle to produce ATP by anaerobic glycolysis. Consequently, low levels of lactic acid were produced which were fairly rapidly broken down. Haematocrit values were low in non-exercised fish, and these increased by over 100% during exercise, falling back to control levels over many hours. This is probably related to the increased oxygen demand during exercise.

The ancient evolutionary history of polyomaviruses

Polyomaviruses are a family of DNA tumor viruses that are known to infect mammals and birds. To investigate the deeper evolutionary history of the family, we used a combination of viral metagenomics, bioinformatics, and structural modeling approaches to identify and characterize polyomavirus sequences associated with fish and arthropods. Analyses drawing upon the divergent new sequences indicate that polyomaviruses have been gradually co-evolving with their animal hosts for at least half a billion years. Phylogenetic analyses of individual polyomavirus genes suggest that some modern polyomavirus species arose after ancient recombination events involving distantly related polyomavirus lineages. The improved evolutionary model provides a useful platform for developing a more accurate taxonomic classification system for the viral family Polyomaviridae.

A comparison of plasma vitamin C and E levels in two Antarctic and two temperate water fish species

Antarctic fish have a high polyunsaturated lipid content and their muscle cells have a high mitochondria density suggesting that Antarctic fish are under greater oxidative stress than temperate water fish. To test this hypothesis, the plasma concentrations of the antioxidant vitamins E and C were measured in two Antarctic fish species, Pagothenia borchgrevinki and Trematomus bernacchii, and compared with the plasma concentrations of these vitamins in two New Zealand temperate water fish species, blue cod (Parapercis colias) and banded wrasse (Notolabrus fucicola). Neither vitamin is known to be synthesised in fish and so must be obtained from the diet. The plasma from both Antarctic fish species had vitamin E concentrations five to six times higher than those found in the two temperate water fish species. However, significantly higher levels of vitamin C were only found in the plasma of T. bernacchii, a benthic Antarctic fish. The average level of vitamin C in the plasma of the cryopelagic P. borchgrevinki was approximately one-third that of T. bernacchii. The T. bernacchii plasma yielded a high range of vitamin C values, possibly reflecting differences in nutritional status among the animals captured. No beta-carotene was found in any of the fish plasma samples studied. The data suggest that even though Antarctic fish live at -1.5 degrees C they may be exposed to greater metabolic stress from free radical mediated oxidation than temperate water species.

Cardiovascular responses to hypoxia in the hagfish, Eptatretus cirrhatus

Simultaneous measurements of cardiac output (Q), blood pressures and blood gases were made in the hagfish, Eptatretus cirrhatus, during exposure to hypoxia. The partial pressure of oxygen in the medium (PIO2) was reduced from 20.7 kPa to 8.0 kPa and then lowered to 5.3 kPa. At a PIO2 of 5.3 kPa there was a 40% increase in Q. Part of the increase may have been due to the increased activity of the animal at low PIO2. In recovery, when the animals were inactive, Q continued to rise to 160% of the control values. At 5.3 kPa, oxygen consumption (as determined by the Fick principle) fell to 29% of the normoxic value and was associated with increased branchial vascular resistance (Rg) and an increased diffusion limitation of the gills (Ldiff). Adrenaline increased heart rate and aortic blood pressures. Increased Rg and Ldiff could be provoked in normoxia by the injection of the beta-adrenergic blocking drug propranolol. We suggest that catecholamines may be involved in the tonic control of gill vasomotor tone.

The effects of fish anaesthetics (MS222, metomidate and AQUI-S) on heart ventricle, the cardiac vagus and branchial vessels from Chinook salmon (Oncorhynchus tshawytscha)

The acute effects of 3 fish anaesthetics (MS222, metomidate and AQUI-S) were investigated on 3 parts of the cardiovascular system of Chinook salmon (Oncorhynchus tshawytscha). All 3 anaesthetics reduced the contractile force of paced strips of ventricular myocardium. MS222 reduced the contractility by almost 75%, and was more potent than metomidate and AQUI-S, which reduced the contractility by about 25%. MS222 blocked vagal nerve transmission to the heart at the normally applied anaesthetic concentration (NAAC) for Chinook salmon, whereas metomidate and AQUI-S required 100 times their NAACs to have the same effect. Using myography, MS222 and AQUI-S caused a maximal 30–40% dilation of EBAs at 10% NAAC, whereas the equivalent effect with metomidate was only seen at 100% NAAC. MS222 again caused the greatest dilation of the ABAs. AQUI-S dilated the ABAs at up to 50% NAAC, but this was reversed so that there was no dilation at 100% NAAC. Metomidate did not affect the ABAs. These data from in vitro and in situ experiments, which generally show inhibitory effects, are used to suggest possible cardiovascular outcomes in anaesthetised Chinook salmon.