Effects of Illumination and Size on Metabolism of Oxygen Consumption, Ammonia and Active Phosphate Excretion in Giant Clam Tridacna crocea

Abstract:

The effects of illumination (5000 lx illumination and darkness) and size [shell length: (63.53±1.22) mm as “small” group, (75.87±1.50) mm as “medium”, and (92.75±3.02) mm as “large”] on the metabolism of dissolved oxygen, ammonia nitrogen and active phosphate in the giant clam Tridacna crocea were studied under laboratory conditions at 24–26℃. The results showed that under illumination, T. crocea released oxygen and absorbed ammonia nitrogen and active phosphate; the metabolism of T. crocea was similar to other bivalve mollusks in the dark. The metabolism rate of individual T. crocea was closely related to the size. Under illumination, the oxygen-production rate and the ammonia nitrogen/active phosphate absorption rate had a highly positive correlation with the size; in the dark, on the contrary, there was a negative correlation between the size and the oxygen production rate and the ammonia nitrogen/active phosphate absorption rate. Under illumination, the metabolic rate of symbiotic zooxanthellae (per gram of dry weight) of T. crocea was negatively correlated with the individual size. In this study, the metabolism of oxygen, ammonia nitrogen and active phosphate of T. crocea was quantitatively correlated with the size and light conditions for the first time. Our results provided basic information on the role of T. crocea in coral reef ecosystems and on the artificial breeding of giant clams.