For the determination of ammonia excretion, the same larvae used for oxygen
consumption were kept in the respirometric cells for 2 h. Ammonia excretion was the
difference of the ammonia concentration in the water in the cells between the beginning
and end of this period. Samples for the determination of ammonia were taken in
Ependorff tubes with sublimated iodine and they were preserved frozen until they were
processed, always less than 12 h after sampling.