This is due to the fact that the muscle fibers of squid are distributed laterally and, although it is easier to tear the squid in the lateral direction along the muscle fibers, the fibers of a torn piece stretch longitudinally and one will have to chew surume thoroughly before swallowing.
これはイカの筋繊維が横方向に走っている為で、横に裂けば裂きやすいが、繊維が長手方向につながってしまうためよく噛まねば飲み込めない。