The PCA applied to urea excretion profiles proved that turbot differed from the other
species, confirming the observations made by Dosdat et al. (1995). Urea excretion
profiles were also different in sea bream, which excreted more urea during daylight
hours. This may be due to a lower activity of this species during the night. In turbot,
purine degradation and uricolysis may not be the only pathway for urea production. The
possible involvement of the urinary bladder in the storage and pulsatile release of urea
needs further investigation. In amphibians, the urinary bladder is known for its high