Rufus M. G. Wells

Physiological stress responses in big gamefish after capture: Observations on plasma chemistry and blood factors

The plasma electrolytes, Na+, K+, Ca2+, Cl- and osmolarities had high values in capture-stressed big gamefish. Blood metabolites measured after stress showed glucose and lactate elevations. The activity of the plasma enzymes alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, creatine kinase and lactate dehydrogenase suggested tissue disruptions following severe capture stress. Haematocrit values and methaemoglobin were high in capture-stressed gamefish. The plasma chemistry of resting and capture-stressed snapper (Chrysophrys auratus) was studied for comparison. Specific differences in plasma biochemistry appeared to be the result of different strategies of fish behaviour during capture.

Comparative physiology of Antarctic fishes

Publisher Summary From the standpoint of a comparative physiologist, Antarctica is a superb natural laboratory providing excellent research opportunities. The unique fish fauna of an entire continent has resulted from the successful colonization of Antarctic waters, and subsequent diversification, by a single major group. The results of these studies on the comparative physiology of Antarctic fishes have implications for a wide range of biological disciplines. The complex of physiological adaptations of notothenioid fishes gives some insight into the reasons for their success as the major group of Antarctic teleosts, and the general failure of other fishes to penetrate south of the Antarctic Convergence. The attempts to understand the effects of temperature on biological processes, and its consequences for the animals themselves, will always be highlighted by the study of extreme environments. This chapter summarizes the progress in Antarctic fish physiology made over the past quarter century, to indicate the exciting potential for further work, and to act as an introduction to new workers in the field.

THE USE OF ENERGY STORES IN THE PUERULUS OF THE SPINY LOBSTER JASUS EDWARDSII ACROSS THE CONTINENTAL SHELF OF NEW ZEALAND

Abstract Nektonic pueruli of the spiny lobster, Jasus edwardsii, were caught from two locations about 20 km apart across the continental shelf on the south east of the North Island, New Zealand. The pueruli were assayed for total protein, glucose, glycogen, and lipid content. Only the lipid content differed between pueruli caught onshore and offshore (mean difference=3.1 mg or 3.4% of dry mass). The average difference in lipid content measured over this distance was used to calculate the rate of energy consumption and timing for pueruli to actively swim from the continental shelf to shore. These results confirmed previous theoretical estimates and indirect measures. Furthermore, the rate of energy consumption would allow all of the pueruli caught offshore to swim to shore based on their total measured lipids. However, some individuals with low energy stores may be energetically compromised at arrival which may affect their subsequent moulting and survival. The results of this study indicate that lipid is the primary format for energy storage of the nektonic puerulus of the spiny lobster and that these lipid reserves have sufficient energetic capacity to allow the puerulus to actively swim the distance across the shelf to settle on the coast.

Blood oxygen transport, rheology and haematological responses to confinement stress in diploid and triploid Atlantic salmon, Salmo salar.

Abstract Diploid and triploid all-female Atlantic salmon (Salmo salar) smolts were challenged with 2.5 h of confinement stress in aerated seawater. Subsequent stress responses were quantified by plasma cortisol, glucose, and lactate, and by the haematological parameters haematocrit (Hct), red blood cell count (RBCC), mean cell volume (MCV), blood haemoglobin concentration (Hb), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), total protein and erythrocyte adenosine triphosphate (ATP). The magnitude of stress responses was similar between diploid and triploid smolts. Triploid smolts displayed a higher MCH, but lower Hb than diploid smolts. The blood oxygen affinity of diploid and triploid fish was similar at 15°C over the pH range 6.76–7.99 and the isohaemoglobin components were identical. The enlarged triploid erythrocytes showed reduced shear-dependence on blood viscosity at constant Hct and are therefore unlikely to contribute to greater peripheral vascular resistance. The results show that despite having fewer, larger erythrocytes, triploids have very similar oxygen carrying capacity and haematological response to stress as diploids. This suggests that the higher farm mortality reported for triploids in response to stress is not generated by their failure to show respiratory homeostasis in the face of stress.

Metabolic characteristics of muscles in the spiny lobster, Jasus edwardsii, and responses to emersion during simulated live transport

The metabolic characteristics of five muscle groups in the spiny lobster Jasus edwardsii were examined in order to compare their anaerobic and oxidative capacities. Enzyme activities of phosphorylase, phosphofructokinase, pyruvate kinase, and lactate dehydrogenase were highest in abdominal muscles supporting anaerobic burst activity. Hexokinase, citrate synthase, and HOAD activities in the leg and antennal muscles indicated higher aerobic potential. Arginine kinase activities were high in all muscle groups indicating that muscle phosphagens are an important energy reserve. Arginine phosphate concentrations in 4th periopod and abdominal flexor muscle from lobsters sampled in the field were higher than any values from captive animals, and approximately five times those for ATP. Muscle lactates were high in captive animals. Responses to emersion during simulated live transport appear to exploit the capacity for functional anaerobiosis and further differentiated the muscle groups. Abdominal muscles were especially sensitive and after 24 h showed significant increases in lactate, glucose, ADP, and AMP. ATP levels appeared to be maintained by muscle phosphagens and raised doubts about the efficacy of the adenylate energy charge in evaluating the emersion response. Haemolymph glucose, lactic acid, and ammonia peaked after 24 h emersion and were largely restored following re-immersion. We propose that arginine phosphate concentrations in the 4th periopod are an appropriate index of metabolic stress, and could lead to improved commercial handling protocols.

Respiration of Antarctic fish from McMurdo Sound

1. Resting rates of oxygen uptake were measured for nine species of unstressed fish living at -1.8 degree C in McMurdo Sound, Antarctica (77-78 degrees S). Interspecific differences in VO2 were correlated with the habits and activity of the fish. 2. The cryopelagic Pagothenia borchgrevinki regulated oxygen uptake down to a critical PO2 of approximately 60 mmHg. The inactive benthic species Trematomus centronotus extracted oxygen to lower PO2 and appeared to have a lesser degree of oxyregulation when the data were analysed using a quadratic model. 3. Cutaneous oxygen uptake in the nototheniids T. bernacchii and P. borchgrevinki amounted to 9 and 17% of total VO2 under normoxic conditions which is less than that reported for scaleless Antarctic fish. 4. The contentious concept of metabolic cold adaptation in polar fish has been reviewed, and the opinion expressed that the phenomenon cannot be dismissed on the grounds of technically incompetent measurement, or through inappropriate extrapolation of data from fish at lower latitudes.

Oxygen binding by the blood and hematological effects of capture stress in two big gamefish: Mako shark and striped marlin

Blood from capture-stressed striped marlin cannot be fully saturated with oxygen in the presence of lactic acid because of a substantial Root effect. Titration of blood to pH 7.6 at 25 degrees C gave an O2 affinity constant, P50 = 17 mmHg. The P50 was highly sensitive to pH showing a Bohr factor phi = delta log P50/delta pH = -0.74. Blood from capture-stressed mako sharks did not show either a Root effect or a significant Bohr effect (delta log P50/delta pH = +0.16). The O2-affinity constant, P50, was 10.6 mmHg at pH 7.6 and 25 degrees C. Hematological measurements following capture gave hematocrit values of 24.2 +/- 8.1% and 32.3 +/- 10.8% for marlin and mako respectively, and high concentrations of blood lactate in both species (15-16 mmol l-1). The O2 transport properties of the blood are discussed in relation to oxygen demand and capture stress.

Effects of stress on plasma cortisol levels and blood viscosity in blue mao mao, Scorpis violaceus (hutton), a marine teleost

Abstract 1. 1. Freshly captured wild Scorpis violaceus had low plasma levels ofcortisol (mean of 3.3 ng/ml). This rose to 30.4 ng/ml following 10 min of confinement stress. 2. 2. Scorpis acclimated to laboratory conditions for up to 21 days after capture had higher mean plasma cortisol levels than freshly captured fish (19.6–38.3 ng/ml). Disturbance during serial netting from a stock tank resulted in a further increase to 73.9 ng/ml over 10–15 min. 3. 3. Tank-acclimated fish exposed to 30–60 nun of confinement stress showed a further increase in plasma cortisol to 276 ng/ml. Serial sampling offish over 60 min of confinement gave similar plasma cortisol levels. 4. 4. Hematocrits were not different in freshly captured, tank-acclimated or acutely stressed fish. Hematocrits and hemoglobin concentrations were, however, lower in fish that were serially sampled after 60 min. 5. 5. Mean corpuscular hemoglobin concentration did not change in response to handling or confinement, indicating that erythrocyte swelling did not occur in response to stress. 6. 6. Fish exposed to 60 min of confinement stress had lower blood viscosity at high shear rates than either tank-acclimated fish or fish exposed to 5 min of confinement. Only part of this effect could be explained in terms of reduction in hematocrit.

A comparison of metabolic stress during air exposure in two species of New Zealand abalone, Haliotis iris and Haliotis australis: implications for the handling and shipping of live animals

Abstract Anaerobic metabolism in New Zealand blackfoot and yellowfoot abalone, Haliotis iris and Haliotis australis , is supported by specific pyruvate reductase enzymes and a moderate intracellular pH buffering capacity. Lactate and tauropine increased, while ATP and energy charge decreased in both species after 24 h air exposure. Responses were most marked in yellowfoot abalone, though allometric analysis revealed the simple explanation that the difference was due to size alone. Thus, small abalone accumulate higher metabolite concentrations and have a significantly lowered energetic status compared with larger specimens similarly exposed to air. These stress responses, which may ultimately affect both meat quality and survival during transport, are evaluated in the context of proposals to culture “cocktail” sized abalone.

Oxygen transport potential in tropical reef fish with special reference to blood viscosity and haematocrit

Abstract Blood viscosity and haematological parameters were compared in seven tropical marine teleosts. Aerobic scope was evaluated from behavioural observations of activity and from the distribution of red muscle. Active species such as trevally had higher haematological values than did less active species, yet corresponding differences in blood viscosity were not evident. The erythrocytes of active fish appeared smaller and their viscosity was less shear-dependent. These observations are considered in terms of optimized oxygen transport potential which was greatest in the most active species. The concept of optimized haematocrit was rejected because all fish had predicted optima that differed from measured values.