Effect of Food Administration on the Metabolism of Regularly Fed and Starved Goldfish
Abstract
Many biological and environmental factors are known to affect the metabolic rate of goldfish. Previous research in the field has shown that consuming food and nutrients leads to an increase in the rate of metabolism among ectotherms. To further this research, our goal is to investigate the immediate effects of food intake on the metabolic rate of goldfish by examining the oxygen consumption of starving fish versus regularly fed, i.e. “normal”, fish. We postulate that upon feeding, goldfish will experience an increase in metabolic rate. We further hypothesize that starved goldfish will have a slightly higher metabolic rate than normal goldfish. Four male goldfish were assigned to one of two experimental groups: group 1, normal goldfish that received 0.1 grams of goldfish food twenty minutes before the measurement of oxygen consumption; and group 2, goldfish that underwent starvation and received 0.1 grams of goldfish food twenty minutes before the measurement of oxygen consumption. Data was analyzed using both a Paired T-Test and an Independent T-Test. Statistical significance was considered at p £ 0.05. Both normal goldfish and starved goldfish demonstrated a significant increase in their respective metabolic rates 20 minutes after feeding. Additionally, starved goldfish had a significantly lower initial metabolic rate than normal goldfish (prior to feeding). However, there was no statistical evidence to suggest a difference between the final rates of metabolism after feeding in either group. This experiment successfully demonstrated an increase in metabolic rate upon administering food to goldfish; however further experimentation will be necessary to determine if feeding a starved goldfish would cause a slightly higher metabolic rate than normal goldfish.
Introduction
Metabolism is a key component in the energy budget of goldfish. Although primarily influenced by mass and water temperature, many other factors have been shown to influence the standard metabolic rate of fishes (Gillooly, 2001). Biological factors such stress, and daily biorhythms or environmental factors such as hypoxia, salinity, toxicity, and pH contribute to the positive and/or negative effects on the rate of oxygen consumption (Spoor, 1946 and Paloheimo, 1966). Our goal is to investigate the immediate effects of food intake on the metabolic rate of goldfish by examining the oxygen consumption of starving fish versus normal fish. Previous research indicates that administering food to a normal goldfish increases the rate of oxygen consumption which thereby increases the rate of metabolic processes (Guinea, 1997). Additionally, it has been found that the feeding of pike (which are also ectothermic,) who had been starved for 3 months resulted in the rate of oxygen consumption and the rate of metabolic processes being increased to levels higher than those observed in freshly-captured “normal” fish (Ince, 1976). Thus, based on this research, we hypothesize that upon feeding, goldfish will have a higher metabolic rate. We further hypothesize that upon feeding, the starved goldfish will have a slightly higher metabolic rate than the normal fish. Specific quantitative analysis of oxygen consumption will allow us to compare the outcomes of starved goldfish and normal goldfish that were fed prior to measurement. In addition, we will gauge the effect of administering food by comparing our results to the starved and normal goldfish prior to feeding.
Methods
Four male goldfish were assigned to one of two experimental groups: group 1, normal goldfish that received 0.1 grams of goldfish food twenty minutes before the measurement of oxygen consumption (n=2); and group 2, goldfish that underwent starvation and received 0.1 grams of goldfish food twenty minutes before the measurement of oxygen consumption (n=2). Each fish was placed in an Erlenmeyer flask (approximately 250 mL) and filled with room temperature water.
Group 2 goldfish underwent a period of starvation prior to experimental manipulation. Each group was given 0.1 grams of goldfish food twenty minutes prior to the measurement of metabolic rate. The initial oxygen content of the water was measured to calculate the initial metabolic rate prior to feeding, and both experimental groups were incubated for a period of twenty minutes. Following this period, the oxygen content of each flask was measured and each goldfish was weighed. The weight of the goldfish, and thereby the corrected flask volume, were used to calculate the overall oxygen consumption of the goldfish during the incubation period. The higher the rate of oxygen consumption per hour per gram of fish weight (O2/hr/g), the higher the rate of metabolism in the goldfish. Data was analyzed in SPSS using both a Paired T-Test and an Independent T-Test. Statistical significance was considered at p £ 0.05.
Results
Goldfish in both treatment groups tolerated the protocol. At 0 minutes, the normal goldfish demonstrated a metabolic rate of 0.259-0.637 ml O2/hr/g. At the same initial time point, the starved goldfish had a metabolic rate of 0.161-0.465 ml O2/hr/g. At 20 minutes, the normal goldfish demonstrated a metabolic rate of 0.303-0.873 O2/hr/g. And at the final time point, the starved goldfish had a metabolic rate 0.372-0.834 ml O2/hr/g. These values can be found in Table 1 and were calculated using: mean +/- standard deviation.
The metabolic rate of normal goldfish upon feeding increased significantly from 0.4481 ml O2/hr/g to 0.5582 O2/hr/g (Table 2, Figure 1). Similarly, the rate of metabolism in starved goldfish demonstrated a significant increase, from 0.3127 O2/hr/g to 0.6031 O2/hr/g, 20 minutes after feeding (Table 3, Figure 2). Additionally, starved goldfish had a significantly lower initial metabolic rate (0.3127 O2/hr/g) than normal goldfish (0.4481 O2/hr/g) (Table 4). Although the metabolic rate of starved goldfish after the incubation period (0.6031 O2/hr/g) was slightly higher than that of the normal goldfish after the incubation period (0.5582 O2/hr/g), there was no statistical evidence to suggest a reportable difference between the final rates of metabolism (Table 5). These results are summed up in Figure 3.
Discussion
The administration of food to goldfish increases metabolic activity as measured by oxygen consumption (Spoor 1946). Extensive studies on Sparus aurata (gilt-head bream) have found feeding to lead to an increase in oxygen consumption rates lasting for approximately 37–39 hours, peaking between 1 and 6 hours. In addition to feeding, however, the exact time course of the change in oxygen consumption was also dependent on temperature, ration size and food distribution. Physiologically, food has been proven to provides amino acids, carbohydrates and lipids that are broken down during digestion to provide as source of energy to the goldfish, thereby increasing metabolism (Guinea, 1997). Our findings of significantly increased metabolism between 0 and 20 minutes are consistent with these previous outcomes, and agree with the hypothesis that upon feeding, goldfish will experience an increase in metabolic rate.
It has also been found that the force-feeding of pike starved for 3 months resulted in liver lipid, muscle glycogen and thus metabolism being increased to levels higher than those observed in freshly-captured (normal) fish (Ince 1976). Based on these findings, we initially hypothesized that that starved goldfish would have a slightly higher metabolic rate than normal goldfish. Although the starved goldfish did show a slightly higher metabolic rate than normal goldfish, there was not enough statistical evidence to consider the results significant thus our data disproved this hypothesis. However, as this conclusion does not agree with previous literature, it would be imperative to re-conduct this study in the future using a larger sample size to produce more accurate, statistically significant results. Other physiological factors, such as stress, lighting, or failure to consume the allotted amount of food could explain the observed variation from our expected outcome by producing either falsely low or falsely high readings in oxygen consumption. As practiced by Bernard Ince in 1976, it may be necessary to force-feed the starved goldfish in order to ensure food consumption, as the starved fish may not voluntarily eat after a long period of starvation.
This study exemplifies a very real scenario for goldfish, as the availability of food in its natural environment varies significantly. Goldfish who are able to attain food will be able to maintain their metabolism, survive, and procreate whereas goldfish who are not able to attain food will experience dangerously low rates of metabolism, and ultimately death which exhibits a natural selection type of effect. Although our experimental design accurately measures the metabolic rate of goldfish in an investigational setting, it is undoubtedly limited. When analyzing our findings, we assume that each goldfish ate the same amount (0.1g) of food; however there is no way to measure exactly how much food was consumed without the implementation of force-feeding. Additionally, to be accurate, the amount of food administered should not be a flat 0.1g, but rather a ratio involving weight of the specimen to ensure equivalent doses. Furthermore, there were many confounding environmental factors, such as stress, water purity, and light exposure that may have influenced the outcome of our oxygen consumption readings.
Although there are many limitations to our experimental design, our model is efficient in showing the increase in metabolic rate upon the administration of food. Future research with the implementation of force feeding, and control of the aforementioned variables could lead to a very worthwhile investigation of the negative effects of starvation on metabolism in goldfish. Ultimately, these results could be used as a basis for clinical exploration of the metabolism on diseases such as anorexia nervosa in humans.
References
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