EFFECT OF OSCILLATORY WATER-FLOW ON BURRO WING BEHAVIORS OF THE JAPANESE SURF CLAM PSEUDOCARDIUM-SACHALINENSIS

This study examined the effects of oscillatory water flow, with refere nce to flow speed and amplitude period, on the burrowing behaviors of the Japanese surf clam Pseudocardium sachalinensis (shell length= 5.7- 41.7 mm) using a vertical water-circulating tunnel. The burrowing spee d of the clam tended to rise with the shell length and flow speed rega rdless of amplitude period and the clam's posture at burrowing toward flow. The relationship between the burrowing speed (Tr: mm/s), shell l ength (L: mm) and flow speed (U: cm/s) was described as V/L=4,66x10(-4 ) U+0.015. A. large number of the clams apparently burrowed in a later al direction toward the flow. The maximum flow speed when the clams co uld burrow into sand ranged from 15 cm/s (amplitude period: 4 s) to 20 cm/s (8-12 s) for the clams with shell length of 4-10 mm, and from 20 cm/s (4 s) to 25 cm/s (8-12 s) for the clams with shell length of 16- 42 mm.