On the roles of schooling, colour and body size for thermoregulatory capacity in aquatic ectotherms

Abstract: For ectothermic organisms, both terrestrial and aquatic, the environmental temperature is imperative for their metabolic processes and finally for their growth and fitness. Previous research have shown that aquatic ectothermic organisms through the process of sun basking, were able to increase their body temperature in comparison with the one of the surrounding water. During this project I studied the possibility that organisms through the combination of sun basking and schooling behaviour can rise the temperature of their surrounding water and as a consequence create their own thermally favourable microhabitat. During this project I investigated whether and how the colour and size of the school’s individuals, the size of the school and the clarity of the water may influence the school effect on water temperature by a series of manipulation experiments. The project took place in the laboratory, where I used physical models of different sizes, colours and densities as proxies for fish. The models were submerged in aquaria with clean water, water that was coloured with dye, or water that was coloured with algae and exposed to artificial light. The results showed that the colour and density of the schools in the aquaria influenced the school effect in the aquaria. Last but notleast, the colour of the water, either artificial (dye) or natural (algae), was an important factor in the rate of the rising temperature in the aquaria by increasing it more rapidly and by reducing the schooling effect from the tubes.