Particle retention efficiency of asari clam Ruditapes philippinarum larvae

Larval food abundance is one potential cause of recruitment variation in benthic invertebrates, including bivalves. Bivalve veliger larvae can clear particles <similar to 10 mu m. However, the particle retention efficiency (PRE) of bivalve larvae differs among species, so is necessary to determine larval food abundance in nature. We investigated the PRE of larvae of the asari clam Ruditapes philippinarum, which recently has greatly decreased in numbers in Japan. Artificially hatched larvae from the umbo to the full grown stage were exposed to natural food assemblages. Larval clearance rates were determined for particles in 32 size ranges from 0.8 to 18 mu m. We observed significant clearance of particles in the similar to 1 to 8 mu m size range, with the highest clearance rates being on 1.4 to 2.0 mu m particles. Larval ingestion of the natural food assemblages ranged from 50 x 102 to 120 x 102 mu m(3) ind.(-1) h(-1), which is below the hatchery food ration, suggesting larval food limitation in nature.