Meeting Abstract

100.3  Monday, Jan. 6 14:15  Do Pacific sandfish (Trichodon trichodon) use a modified two-phase respiratory pump for rapid burial? MACDONALD, I/A*; FERRY, L; SUMMERS, A; GIBB, A/C; Northern Arizona University; Arizona State University; University of Washington; Northern Arizona University iam26@nau.edu

Many fishes bury themselves to evade predators and ambush prey. Unlike other species, which laterally undulate to embed themselves in the substrate, the Pacific sandfish buries itself ventral surface first. We hypothesized that Pacific sandfish use a modified two-phase respiratory pump to force water into the substrate during burial. We recorded 5 fish from dorsal and lateral views descending into white sand seeded with black sand particles. During a burial event, each fish produced a series of respiration-like movements and these movements were associated with pulsatile periods of descent into the substrate; rapid descent occurred in concert with compression of the paired opercles. A cycle of burial behavior differed from a normal respiratory cycle in that the gape and opercular compression cycles took twice as long as a typical respiratory cycle. Pacific sandfish also produced repeated cycles of large-amplitude dorsal rotation of the cranium, which are not seen during respiration. Cranial rotation likely increases the volume of water passing through the head by first enlarging the buccal cavity and then by forcing the water posteriorly, into the opercular cavity. Subsequent compression of the opercles forces water out of the head and into the substrate. By forcing water into the sand, it appears that Pacific sandfish increase the interstitial space between sand grains, enabling sand to behave like a fluid. In this fluid-like state sand exhibits a decrease in frictional forces as well as a decrease in its ability to support weight, which will combine to allow the sandfish to descend rapidly into the substrate and hide from its predators.