Transverse sarcomere splitting. A possible means of longitudinal growth in crab muscles.

Abstract

Transversely split sarcomeres were seen in mouthpart muscles of the blue crab [Callinectes sapidus] in the EM. Sarcomeres split only at the H zone. Two new sarcomeres were formed by a Z disk which appeared in the H zone of the splitting sarcomere. Splitting may involve breaking of the thick filaments in the H zone, elongation of these filaments and formation of both new actin filaments and Z-disk materials. Sarcomere splitting allows longitudinal growth of muscle cells without lengthening of sarcomeres and concomitant changes in contractile properties.