Connective Tissue in Squid Mantle Is Arranged to Accommodate Strain Gradients
Jessica A. Kurth, Joseph T. Thompson, William M. Kier 2014 (membership but free to join)
Abstract
Jessica A. Kurth, Joseph T. Thompson, William M. Kier 2014 (membership but free to join)
Abstract
The hollow, cylindrical shape of many soft-bodied animals results in nonuniform circumferential strain across the muscular body wall as the body diameter changes. This could complicate reinforcement with connective tissue because fibers in one region of the body wall must accommodate greater strain than those in other regions. We investigated this issue in the mantle of the squid Doryteuthis pealeii. During escape jet locomotion, the decrease in diameter during the jet requires circumferential strain at the inner surface of the mantle wall to be 1.5 times greater than that at the outer surface of the mantle wall, with a continuous gradient of strain between the two surfaces. We predicted that, to accommodate the greater strain, the intramuscular collagen fibers near the inner surface would either be arranged in a different manner or would have different mechanical properties from fibers near the outer surface. We observed a different arrangement: when the mantle was contracted, fibers from near the inner surface of the mantle wall were significantly more folded than the fibers along the outer surface. When the mantle was fully expanded radially, all of the fibers straightened almost completely, with no significant difference in folding between the inner and outer fibers. The modification of the connective tissue network in the mantle in response to a nonuniform distribution of strain may not be limited to squid, but may be important in other soft-bodied invertebrates and in the walls of blood vessels.