F. Ali et K. Nakamura, Metabolic characteristics of the Japanese clam Ruditapes philippinarum (Adams & Reeve) during aerial exposure, AQUAC RES, 31(2), 2000, pp. 157-165
Some metabolic end-products in tissues and physiological parameters of haem
olymph of the Japanese clam Ruditapes philippinarum (Adams & Reeve) were in
vestigated under aerial exposure at 15 degrees C with low relative humidity
(RH) (22%) or high RH (91%). Acclimated clams in water at 15 degrees C wer
e used as a control and to supply the low or high RH experiment. The low RH
experiment was conducted at air exposure for 50h (LHS50), and the high RH
experiment for 50h (HH50) and 100h (HH100) Accumulation of succinate and al
anine in the tissues proved that the clam shifted its metabolism to anaerob
iosis. Lactate accumulation did not occur. Glucose concentrations in tissue
s increased slightly during exposure except for HH50. The total free amino
acid contents (363-410 mu mol g(-1)) were higher than those of glucose (530
-804 mu mol 100 g(-1)), suggesting that the free amino acids might play a m
ore dominant role in the metabolism. Increase in the haemolymph pCO(2) did
not influence the acid-base balance in the haemolymph during exposure at bo
th humidity conditions. Increase in the haemolymph ammonia from 48.2 to 57.
1 mu mol 100 g(-1) and to 131.0 mu mol 100 g(-1) at LH50 and HH100, respect
ively, suggested that ammonia might function as an important buffering fact
or during aerial exposure. Retention values of the haemolymph pot even at t
he longest exposure time (16.30 mmHg at LH50 and 14.69 mmHg at HH100) indic
ated that the clams depend partially on some aerobic manner.