Oxygen uptake and nitrogen excretion of juvenile Scylla serrata at different temperature and salinity levels

Oxygen uptake (O-2 mg/g/h), ammonia-N excretion, urea-N excretion, organic-N excretion, and total nitrogen excretion (N mu g/g/h) of juvenile Scylla serrata (Forskal) (0.49 +/- 0.11 g wet weight) increased at progressively higher levels of temperature in the range of 16-32 degrees C at 4 salinity levels (15, 20, 25, and 30 ppt). Oxygen uptake, organic-N excretion, and total nitrogen excretion were lowest at 25 ppt. Ammonia-N excretion decreased, whereas urea-N excretion increased at higher levels of salinity. It is concluded that juvenile S. serrata changes its nitrogen metabolism under different salinity and temperature environments, and that there is a shift of nitrogen excretion from ammoniotelism to ureotelism at higher salinity levels.