The differentiation of crayfish muscle fibers during development

As the length (x, mm) of the propodite segment of a crayfish cheliped doubles, the average diameter of the opener muscle fibers also doubles, whereas average fiber length (y, mm) is given by y = 0.16 × + 0.5. Fiber length is increased by the continuous addition of new sarcomeres in propodites 6–22 mm long; in propodites of less than 6 mm, about half the linear growth can be accounted for by increases in sarcomere length. Cable properties of opener muscle fibers differ from those of vertebrate fibers. In a claw of any given size, length constant is not correlated with fiber diameter, muscle input resistance is not proportional to the two‐thirds power of the diameter, and mjp amplitude is independent of input resistance. Electrical properties of opener fibers change during growth, but the extent of the change is not predictable from classical cable equations.