The influence of body size, habitat and diet concentration on feeding of Laternula marilina Reeve

A Chinese duckbilled marine clam (Laternula marilina Reeve) was cultured in a simulated natural culture system for the preliminary determination of its physiological energetics. The results showed that both clearance rate (CR) and ingestion rate (IR) were related exponentially to body size (flesh dry weight, W) as described by the equations CR=0.49W0.65, IR=0.96W0.57. Body size had no effect on assimilation efficiency (AE) at water temperatures of 10(degree)C, 16(degree)C and 23(degree)C, but within this range AE significantly increased with increasing water temperature. It was found that L. marilina performed in feeding behaviour far better when natural substrates conditions were provided. On a sand or silt substrate both CR and IR were two times higher than on an uncovered tank bottom. AE was also improved when sand (13.12% increase) or silt (14.19% increase) was provided. It is evident in our results that within the range of diet (as particulate organic matter, POM) concentration of 2.30+-0.21 to 6.20+-0.13 mg POM L^-1 the relationships between POM and CR and IR were exponential and as described by the equations CR=0.29 [POM]0.75, IR=0.33 [POM]1.34. In these experiments, the diet concentration threshold of pseudofaecal excretion was found to be 3.05 mg POM L^-1. There was no marked influence of diet concentration on AE, which was consistently about 60%.