The effect of some stressors on the metabolism of the plaice, Pleuronectes platessa L.

White, Ann (1991). The effect of some stressors on the metabolism of the plaice, Pleuronectes platessa L. MPhil thesis The Open University.

Abstract

The influence of environmental stressors on the concentrations of various serum components was examined in the plaice (Pleuronectes platessa L.). These factors included capture, transportation and short-term starvation following arrival in the aquarium, where the effects of normal and exacerbated disturbance were also examined. The serum lipid class and concentration in male and female plaice caught at various seasons was investigated in relation to the composition of the gonads, as an example of the effects of the reproductive cycle on the nature of the circulating lipids.
Plaice were fed fresh mussel flesh for 7 months, at the end of which time, serum/plasma components were measured after 24 h without food. No significant differences were found between those values and concentrations found in wild fish 24 to 48 h post-capture (without feeding).
After capture and transportation to the aquarium, plaice were maintained for 15 days without feeding. The decrease in glucose and cortisol levels are perhaps due more to recovery from capture and transportation, rather than to lack of food.
Only cortisol levels proved sensitive to routine aquarium disturbance and in fish exposed to agitation for 1 h, but significant differences between short- and long-term physical disturbance over a 24 h period were also found for serum glucose, total cholesterol and free cholesterol. Serum non-esterified fatty acids (NEFA) concentrations, however, began to increase 3 h after the onset of disturbance, and high levels were sustained in fish from both regimes over the 24 h period. In plaice under reduced oxygen conditions for a short period of time, increases were found in circulating levels of NEFA, cortisol, free cholesterol and lactate, but there was a decrease in the serum glucose concentration, when compared to control fish.
The intraperitoneal (i.p.) injection of cortisol had no significant effect on serum components measured after 24 h and 4 days, whereas injection of adrenalin caused an increase in serum NEFA, glucose and cortisol concentrations after 24 h and a decrease in serum NEFA after 4 days. The i.p. injection of endotoxin resulted in a decrease in serum NEFA (4 days) and glucose (24 h) levels, and an increase in serum cortisol (24 h), when compared with saline injected controls.
Total lipid, total cholesterol, free cholesterol, triglycerides, phospholipids and NEFA were measured using commercial kits, validated against standard reference methods.

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