Meeting Abstract
In marine sediments, burrowing and feeding by infauna (e.g. polychaetes, burrowing shrimp) result in sediment mixing and benthic-pelagic exchange of solutes, and such bioturbation plays a key role in benthic ecosystem dynamics. Although many infaunal taxa are equipped with chemosensory structures (e.g. polychaete nuchal organs), little is known about how infaunal burrowers detect and respond to chemical cues below the sediment surface. In a series of behavioral experiments, we examined responses of the polychaete Alitta virens to subsurface chemical cues. Using time-lapse photography and time-resolved, digital, particle-imaging velocimetry (PIV), we tracked worms’ positions relative to the position of clam juice injected into the sediment (no-flow experiments), or released via subsurface drip (flow-through experiments). In no-flow experiments, worms with blocked (super-glued) nuchal organs did not respond positively to the cue, but intact worms (control) and worms with superglue on the 3rd chaetiger (glue control) did. These results support the hypothesis that nuchal organs mediate subsurface responses to chemical cues. PIV provided information about worms’ subsurface activity and revealed subtle differences in burrowing dynamics for intact worms responding to a subsurface drip of seawater or clam juice in flow-through experiments. More worms increased average path speed in response to clam juice than in response to seawater, but overall, mean path speeds were not significantly different. Worms responding to clam juice had straighter paths (i.e., net-to-gross-displacement ratio closer to 1) compared to those responding to seawater. Supported by NSF grant OCE0851172 to P.A.Jumars and SML.
