Exposure to a high concentration of salinity caused a great increase in blood osmotic pressure and death of the guppy. To elucidate the strain differences of osmoregulation in sea water, blood osmotic pressure was measured after transfer from freshwater to 15 ppt dilute sea water in 13 different strains of the guppy. Blood osmotic pressure increased and peaked at 24 h after the transfer and then decreased to a level comparable to that in freshwater. Although the blood osmotic pressure in freshwater did not differ among strains, the values 24 h after transfer to 15 ppt dilute sea water demonstrated that the blood osmotic pressure was largely different among strains. A significant inverse correlation was observed between the sea water tolerance (mean survival time in 35 ppt sea water) and the blood osmotic pressure at 15 ppt dilute sea water. This suggests that the strain differences in sea water tolerance depend on differences in osmoregulatory function.
- Sea water tolerance
- Strain difference