The bladder moon snail, Glossaulax didyma, is a carnivore and predator of bivalves, especially the commercially important asari clam, Ruditapes philippinarum. However, little information is available on natural predators against this naticid gastropod. We found small shells similar in appearance to bladder moon snail larvae, from the feces of pen shells, Atrina lischkeana, collected in Isahaya Bay on Kyushyu Island in western Japan. Ingestion of the snail larvae by pen shell has not been reported previously. To clarify if A. lischkeana can ingest the larvae of G. didyma, the larvae were experimentally fed to pen shell. Dead but incompletely digested G. didyma larvae were found in the feces of A. lischkeana after 1 day, showing that the pen shells can ingest the snail larvae, which may be potentially controlling the population of this predatory gastropod.
