Meeting Abstract
P2.86 Sunday, Jan. 5 15:30 Extraordinary elongation and mechanical properties of the body wall of the burrowing sea cucumber Leptosynapta clarki LEE, H.R.*; MERZ, R.A.; Swarthmore College, Pennsylvania ; Swarthmore College, Pennsylvania hlee3@swarthmore.edu
The movement and locomotion of an animal are governed in part by the mechanical properties of its body wall. Leptosynapta clarki, a burrowing sea cucumber, collected from False Bay, San Juan Island, WA, extends its body nearly 3 times its minimum length as measured using time-lapse video in a laboratory setting. Observations in cryolite revealed that it extends by a combination of whole body peristalsis and tentacular crawling. Individual L. clarki whose tentacles were removed were only able to extend twice their minimum length and could not burrow while those with intact tentacles extended 3.4 times their minimum length. This indicates that the oral tentacles are required for extensive elongation and burrowing. Tensile tests were performed parallel to the anterior-posterior axis on sections of intact, cylindrical body wall (obtained by removing the anterior and posterior ends from anesthetized animals and leaving the viscera in place) and on isolated longitudinal strips of body wall. Using extension rates of either 2 mm/min (comparable to the extension rate achieved by L. clarki) or 50 mm/min neither stiffness nor strength of cut strips of body wall were affected by the rate of extension. In contrast, samples of cylindrical body wall were 3 times stiffer and 4 times stronger when pulled at the faster rate. Creep tests on samples of cylindrical body wall confirmed its viscoelastic behavior. These results suggest that viscoelastic elements in the body wall of L. clarki might have been disrupted when it was cut longitudinally or when the internal organs were removed. Since the natural range of maximum extension and the maximum strain from mechanical testing were very similar, it appears that L. clarki is operating near the maximum capacity for strain of its body wall.
