Impacts of temperature and salinity on oxygen consumption rate and ammonia excretion rate in juvenile whelk Neptunea cumingii

The effects of temperature and salinity on respiration and excretion were studied in juvenile whelk Neptunea cumingii with shell length of 3.41 cm ± 0.25 cm by an experimental ecological method.The results showed that the salinity and the temperature led to significant influence on the oxygen consumption rate,ammonia excretion rate and O∶ N in the juveniles( P 0.01).Within a given salinity,the oxygen consumption rate and ammonia excretion rate were found to be increased with elevated salinity first,and then decreased in the treatment groups.The oxygen consumption rate was increased with elevated salinity at a salinity range from 19 to 34,and decreased at a salinity of over 34.The ammonia excretion rate was increased with increase in salinity at a salinity range from 19 to29,but decreased at a salinity of more than 29.The relationship between oxygen consumption rate( RO) and the salinity( S) was expressed as RO=-0.0006S2+ 0.0382S-0.4622( R2= 0.9115); relationship between the ammonia excretion rate( RN) and the salinity( S) was described as RN=-0.0001S2+ 0.0049S-0.0451( R2= 0.5529).In the temperature experiment,both oxygen consumption rate and ammonia excretion rate in the juveniles in the treatment groups were found to be increased with rising temperature first,and then decreased,the maximal oxygen consumption rate at 20 ℃ and the maximal ammonia excretion rate at 25 ℃.The relationship between consumption rate( RO) and temperature( T) was expressed as the formula:RO=-0.0014T2+ 0.0514T-0.2074( R2= 0.8017); and the relationship between ammonia excretion rate( RN) and temperature( T) was described as the formula RN=-0.0013 T2+ 0.0078T + 0.0109( R2= 0.8260),indicating that the optimum temperature for the survival of the juveniles is 20 ℃ and suitable salinity from 29 to 34.