Metabolic Rate vs Light Intensity

The aim of the experiment

The aim of this experiment was to see how different light intensities affected the metabolic rate of manduca sexta caterpillars. Light has been shown in the literature to affect animal behavior, especially by increasing food searching and capture rates. The caterpillars were subjected to various trials under LED spotlight, ambient light, and low light conditions, and the difference in oxygen amount was reported for further study to decide if the test hypotheses were supported.

Impact of light on metabolism

Light has a significant impact on the rate of metabolism in various organisms. This is due to the fact that high light intensities increase the activity of enzymes and the rate of metabolism. According to Byron (1981), terrestrial invertebrates’ pigmentation functions in the optimization of solar warming, and reports that there is higher metabolic rates in darkly pigmented copepods in the light, but copepods that are lightly pigmented do not. Porter (2001) reports increased activity of walleye Pollock with increased light, which affects respiration rate and its energetics. Hubbs & Blaxter (1986) asserts that light is an important factor for most fish larvae to feed, and Batty (1987) notes that light intensities influences the success of capture, activity, prey searching rate and feeding bouts duration.

Research question

The research question is:

How does varying intensities of light affect metabolic rate?

Hypotheses

The hypotheses of this study are:

If the intensity of light has an impact on the caterpillar, then the metabolic rate will increase.

If light intensity has no effect on the caterpillar then the metabolic rate will not change.

Method

Five 9.3 cm tall glass vials with stoppers were used. In addition, 1ml serological pipette was used. This experiment used tobacco hornworm or Manduca sexta caterpillars with the same pigment to test if the metabolic rate will generally go up under high light intensity. One caterpillar was included in each trial with different light intensities at room temperature. The light intensities included LED flashlight, ambient light and low light. Each trial had soda lime encased in a cotton ball and wrapped in a paper towel. Initial oxygen volume was measured and the vials covered with an aluminum foil for 5 min in a water bath, after which the final oxygen was measured and results recorded in a table. The trials were repeated under different light intensities and the results were recorded.

References

Batty, R. S. (1987). Effect of light intensity on activity and food-searching of larval herring, Clupea harengus: a laboratory study. Marine Biology, 94(3), 323-327.

Byron, E. R. (1981). Metabolic stimulation by light in a pigmented freshwater invertebrate. Proceedings of the National Academy of Sciences, 78(3), 1765-1767.

Hubbs, C., & Blaxter, J. H. S. (1986). Ninth Larval Fish Conference: Development of Sense Organs and Behaviour of Teleost Larvae with Special Reference to Feeding and Predator Avoidance. Transactions of the American Fisheries Society, 115(1), 98-114.

Porter, S. M. (2001). Effects of size and light on respiration and activity of walleye pollock (Theragra chalcogramma) larvae. Journal of experimental marine biology and ecology, 256(2), 253-265.