Biology

If you turn up the heat I’ll have no heartbeat

Gouws, M.J., Stellenbosch University, South Africa

Daphnia are ectothermic animals and therefore their body temperature is the same as the water they are floating in. We were determining the effects of different environmental conditions on the heartbeat rate of the Daphnia. The chemical reactions that occur in the cells of Daphnia rely on certain enzymes or proteins to help the reactions proceed. Enzymes only work effectively in optimal conditions so temperature influences the Daphnia metabolic function. At room temperature the Daphnia heartbeat rate and metabolic rate stayed constant. In cold temperatures the Daphnia heartbeat rate and metabolic rate decreased. In warm temperatures the heartbeat rate and metabolic rate of the Daphnia increased substantially. Our findings suggest that the Daphnia does experience changes in their environment and their metabolism does increase or decrease as the temperature changes.

1. Introduction

One of the essential challenges for animals is maintaining their internal environment at temperatures that can be tolerated by body cells. Animal cells can only continue to exist within a temperature range from about 0- 45 degrees Celsius. If the temperature is far below 0 ⁰C the lipid bilayer of the membrane changes from a liquid to a frozen gel, which interferes with the cells important functions and the ice crystals damages and destroys the cell’s organelles. If temperatures advance to 45 ⁰C, the kinetic motion of molecules increases so rapidly that most proteins and nucleic acids unfold from their original form. Either of these extremes leads to cell death. Animals that obtain their heat from their external environment are known as ectotherms. Daphnia are ectothermic animals and therefore their body temperature is the same as the water they are floating in. They live in temperate environments where temperatures fall within a range that creates optimal physiological performance....