68.3 Jan. 7 Feeding and burrowing mechanics of lugworms, Arenicola marina and Abarenicola pacifica WETHEY, David*; WOODIN, Sarah; Univ. of South Carolina; Univ. of South Carolina email@example.com
Lugworms are subsurface deposit feeding polychaete annelids, who feed head-down in marine muddy-sands. These animals use hydraulic mechanisms to create and irrigate their burrows and to feed. We used simultaneous time-lapse photography and recordings of porewater pressure fluctuations to determine the mechanics of feeding. During feeding, lugworms generate positive pressure transients in the porewater of up to 800 pascals, which cause the sediment to crack in the region of the feeding zone. These cracks propagate to the sediment surface, and when pressurized, they allow sediment grains to fall from the surface down to the feeding zone of the animal. Repeated action of this sort creates a pit on the surface of the sediment. Burrowing generates porewater pressure fluctuations of up to 1200 pascals, as the animals fluidize the sediment in front of their heads in order to penetrate it. Defecation generates pressure fluctuations up to 1000 pascals, as the animals fluidize sediment in the tail shaft of their burrow. The European species Arenicola marina and the US west coast species Abarenicola pacifica use very similar hydraulic mechanisms in their activities. Laboratory and field measurements with pressure sensors indicate that unrestrained animals in the field carry out these activities at the same rates and using the same mechanisms as animals in the lab.