112.1 Saturday, Jan. 7 Tuning of Mantle Connective Tissue to Non-Uniform Strain in the Squid Doryteuthis pealeii KURTH, J.A.*; THOMPSON, J.T.; KIER, W.M.; University of North Carolina, Chapel Hill; Franklin and Marshall College, Lancaster, PA; University of North Carolina, Chapel Hill firstname.lastname@example.org
The mantle of squid includes networks of intramuscular (IM) connective tissue fibers that store and release energy to augment ventilation and jetting. Recent studies have shown that the mantle experiences significantly greater circumferential strain on the inner lumen surface compared to the outer lumen surface as it expands and contracts. Our goal was to determine how one network of IM fibers, the IM-3 fibers, accommodates this strain gradient. The IM-3 fibers run parallel to the circular muscle fibers that power mantle contraction. They appear folded at rest but straighten during mantle hyperinflation to store elastic energy and resist further mantle expansion. We hypothesized that the IM-3 fibers near the inner surface would show more extensive folding than the outer fibers to accommodate the strain gradient and maximize elastic energy storage. We used sonomicrometry to determine the diameter of the mantle during hyperinflation, and maximal and intermediate degrees of contraction. We fixed rings of mantle tissue at each of the three states then embedded and sectioned the tissue using glycol methacrylate plastic. We compared the degree of IM-3 fiber folding between the inner and outer regions with a dimensionless “folding index,” by dividing the full length of the folded fibers by the straight-line distance between the fiber ends. In the intermediate and maximally contracted mantle tissues, the IM-3 fibers near the inner surface of the mantle were significantly (p<0.05) more crimped than the fibers along the outer surface. In the hyperinflated mantle, folding of the inner and outer IM-3 fibers did not differ (p>0.05). Our data show that differences in the degree of folding of the IM-3 collagen fibers accommodate the strain gradient. Supported by NSF IOS-0951067.