Meeting Abstract

P2.49  Saturday, Jan. 5  Cranial movements of the Pacific Sandfish are coupled with descent into the substrate: Are fish fluidizing sand using the opercular pump? MACDONALD, I.A.*; GIBB, A.C.; Northern Arizona University; Northern Arizona University iam26@nau.edu

Many fish use burial as a method of avoiding predation and remaining cryptic in order to ambush prey. The Pacific sandfish, Trichodon trichodon, however, exhibits an unusual mode of burial when compared to many other sand burying fishes because it descends abdomen first into the sand while producing body bending in the lateral-medial plane and in the dorso-ventral plane. Based on our initial observations of the burial cycle, we hypothesized that dorso-ventral movements of the cranium assist the sandfish in burrowing into the sand. To quantify both cranial and body movements during burying, we used high-speed videography to extract kinematic variables. Sandfish took ~8 seconds to complete their burying behavior; during this time they and underwent ~30 cycles of cranial rotation, where the average dorsal neurocranial rotation was 5° and the magnitude of the rotation increased over time . Periods of cranial rotation occurred just before intervals in which the body descended into the sand and maximum gape consistently occurred at the same time as peak neurocranial rotation. In addition, the operculae were maximally abducted as the cranium rotated upward, and were adducted as the cranium rotated back downward . The tight coupling of cranial rotation, gape and opercular movements with descent of the body into the sand suggests that movements of the head play a key role in the sandfish burial cycle. Although it is still unclear how the body and paired fins contribute to the burying behavior, our preliminary analysis suggests that sandfish may be forcing water out of the opercular cavity into the substrate, thereby fluidizing the sand and enhancing their ability to penetrate it quickly.