ENVIRONMENTAL FACTORS AFFECTING THE FEEDING PHYSIOLOGICAL ECOLOGY OF MANILA CLAM, RUDITAPES PHILIPPINARUM (ADAMS ET REEVE, 1850)

Abstract

Feeding physiological traits (ingestion rate IR , clearance rate CR and absorption efficiency AE ) of Manila clam, Ruditapes philippinarum, were studied within laboratory in static systems. The results obtained are as follows . (1) Relationships between IR, CR and body size were expressed as: IR=0.98W 0.56 (R 2=0.97);CR=0.47W 0.63 (R 2=0.90) . (2) IR, CR and AE of Ruditapes philippinarum in sand substrate were significantly higher than those in the environment without sand substrate (ANOVA, p 0.05). (3) CR increased with higher concentrations of diet but decreased sharply if the concentration exceeded a definite value (7.31±1.36)mg POM/L. IR has the same trend as CR but decreased smoothly after exceeding the definite value (8.79±0.24)mg POM/L. This indicates that Manila clam possesses the inherent ability of regulating ingestion and clearance rates responding to the external diet conditions. (4) Diet concentrations and body size had no significant effect no AE . (5) The threshold concentration of diet leading to pseudofeces production in Manila clam [shell length (3.53±0.02)cm; dry tissue weight (0.41±0.02)g] was around 2.16mg POM/L.