The development and differentiation of two muscle fiber types in the squid Sepioteuthis lessoniana will be studied. First, transmission electron microscopy will be used to document the differentiation of the cross-striated muscle cells of the tentacles and the obliquely striated muscle cells of the arms. Second, the differentiation of these two muscle cell types will be correlated with behavioral changes that occur during development and growth using high speed video recording of prey capture. Third, immunocytochemical techniques will be used to document the pattern and timing of expression of alpha-actinin and paramyosin, proteins important in determining the dimensions and organization of the muscle cell filaments. This integrated approach to muscle fiber differentiation will provide the most comprehensive account of cephalopod muscle development to date. It will afford a unique opportunity to study the transition between two muscle striation types and will examine the significance of the structural characteristics of muscle cells specialized for a particular function. In addition, it will examine the mechanisms controlling the assembly of two distinct muscle cells types during development and will, therefore, provide fundamental insight into the mechanisms of muscle cell growth and development. Because the study will integrate analyses at several levels of organization, the physiological significance of the diversity of structural and biochemical components of muscle can be explored precisely.
