Some effects of testosterone on cichlid fish, Cichlosoma bimaculatum (Linnaeus) Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/05741v751

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  • The effects of testosterone were studied on the tropical fish, Cichlasoma bimaculatum. Growth experiments were designed to determine how testosterone influenced the food consumption and growth of fish. Starvation experiments were designed to show the effects of testosterone on the basal rate of utilization of body energy stores and to establish what effect the anabolic steroid has when anabolism is reduced by the absence of metabolites from food. During the course of the experiments data were collected on wet weight, dry weight, fat, ash, protein and water content and on heat of combustion for control and testosterone treated fish. Four experiments were conducted where cichlids were starved, some as controls and some continuously exposed to testosterone 1:1,000,000. Wet weight, dry weight, weight of crude fat, weight of ash and the water content per cichlid usually decreased during starvation in controls and in the cichlids exposed to testosterone. Water content varied irregularly with reference to protein. Protein usually dropped where as water content dropped clearly in only one control experiment, did not alter markedly in two and increased in one. The testosterone treated fish tended to accumulate more water than did controls. Considerable variability was noted in the data. Much was due to an uneven distribution of cichlids with respect to weight among various groups and subgroups. Despite precautionary measures it was very difficult to maintain true starvation conditions. Some nonfilterable organic materials in the water as well as algae and minute insects may have been a source of food to the starving fish. More evident however, was the food made available as the result of the death of fish. On several occasions there was evidence of cannibalism, both in control and testosterone treated groups. The death of a fish, besides affording food to starving cichlids, introduced an error in the direction of increasing the average if a small fish died, and of decreasing the average if a Larger fish died. On the basis of calories disappearing during starvation, it was shown that starvation and starvation plus testosterone altered the composition of cichlids and decreased the heat of combustion per gram of cichlid. The testosterone treated fish were usually altered to a greater extent. Two growth studies were conducted where some cichlids were fed essentially ad libitum and utilized as controls, and others fed and continuously exposed to testosterone 1: 1, 000, 000. Dry weight in four out of six available comparisons was lower in testosterone treated fish than in controls; in one case the dry weights were similar and in one case the control cichlids had the higher dry weight. Protein was lower in five out of six available comparisons in the testosterone treated fish and were similar in one comparison. The control cichlids fed tubificids accumulated higher amounts of fat than cichlids fed and exposed to testosterone. The amount of food consumed per testosterone treated fish at each sample period was less than for the control fish. Starvation did not significantly alter the caloric equivalent per mg of dry matter. The caloric equivalent was higher in cichlids fed tubificid worms than in cichlids fed commercial fish food. Testosterone increased the caloric content per mg of nitrogen in the fish fed tubificid worms and this possibly indicates an anabolic action with formation of proteins with amino acids high in carbon and hydrogen and low in nitrogen and oxygen. During the fourth starvation experiment additional cichlids were used in order to investigate changes in lipids with starvation and testosterone as well as changes in fatty acid composition. There are some significant alterations in testosterone treated cichlid lipids beyond the alterations produced by starvation alone. The glycerides are reduced much more in the treated cichlids and also sooner. There was in general a reduction in fatty acids amounts in the treated fish. The greatest reduction in fatty acids occurred in fatty acids 16: 0, 16: 1, 18: 0, 18: 1 and 18: 2.
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