Membrane resistance change induced by nitrate and other anions in long and short sarcomere muscle fibres of crayfish

Abstract

1. 1. Ultrastructural features of muscle fibres with long and short sarcomeres from a crayfish walking leg were compared by electron microscopy. The short sarcomere fibres possessed a more extensive system of transverse tubules and diads than the long sarcomere fibres. 2. 2. The membrane resistance of both types of fibre increased when nitrate, bromide or thiocyanate was substituted for chloride in the bathing solution. 3. 3. The increase in membrane resistance was greater for the short sarcomere fibres. 4. 4. The more numerous transverse tubules and diads of the short sarcomere fibres probably provide a higher membrane anion conductance, and a greater sensitivity to the effects of anions which are less permeant than chloride.