Graduate Thesis Or Dissertation
 

Temperature and the bioenergetics of Cichlasoma bimaculatum

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  • One means of evaluating the temperature requirements of an animal is to determine changes temperature causes in the uses and losses of energy and materials in the food the animal consumes. To develop energy budgets for cichlids (Cichlasoma bimaculatum) at different temperatures (20, 24, 28, 32 and 36 C) data were obtained on food intake, growth (total, fat, and protein), fecal losses, maintenance requirements, and other uses and losses of energy and materials including specific dynamic action, activity, and nitrogen excretion. Starvation experiments were conducted to provide information on the metabolic cost of existence and on adjustments in body composition in the absence of food. Energy expenditure during starvation, estimated from heat of combustion data, was found to increase linearly with temperature over 4, 13 and 20 days of starvation. The caloric cost of existence per fish per day was greatest during the first four days at all temperatures and decreased as starvation was prolonged to 20 days. Caloric losses, and dry weight losses showed essentially the same thing. Protein catabolism increased regularly with temperature and decreased slightly with duration of starvation. Fat catabolism did not vary significantly with temperature but decreased markedly as starvation was prolonged. Food intake, growth, and food conversion efficiency varied greatly with changes in temperature. Cichlids were fed ad libitum on small aquatic worms of the genus Tubifex. For food consumption as well as growth, the optimum temperature dropped from 32 to 28 to 24 C as the experimental period was extended from 5 to 12 to 19 days. Optimum growth in dry weight and calories occurred at the same temperatures. Growth of cichlids through time at 20 and 28 C was nearly linear; at 24 C the curve was exponential. At 32 and 36 C, the growth curves rose and then declined. When the fish were held separately during the experiment, food conversion efficiency of cichlids was highest at 20 C and decreased with increasing temperature. Efficiencies decreased with duration of the experiment. When fish were held in groups during the experiment, efficiency was low at both high and low temperatures. The guts of the cichlids were found to contain food up to 30 hours after an ad libitum meal at all temperatures. They were reasonably empty after 36 hours. Thus, no significant correlation was found between temperature and the length of time necessary for the guts to empty. Food material not absorbed was measured by wet combustion. Percentages of absorption of unrestricted rations were found to be 83, 84, 88, 85 and 69 at 20, 24, 28, 32 and 36 C. Percentages of food absorption were much higher on the restricted ration than on the unrestricted ration. Absorption appears to have been optimal at 28 C. Specific dynamic action (SDA) was estimated at different temperatures by taking the difference between oxygen consumption of unfed and fed cichlids at the same levels of activity. SDA represented 22, 20, 19, 33 and 33 percent of the food consumed at 20, 24, 28, 32 and 36 C, when the fish were swimming at 4 cm/second. SDA was generally complete within 36 hours after feeding. Graphs showing energy and material intake, utilization, loss, and scope for growth at each temperature during different experimental periods were developed both in terms of calories per fish per day and calories per gram of fish per day. The evidence suggests that the optimum temperature for growth of this cichlid is near 24 C.
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