9728707 Kier Comparison of striated muscle cells from a diversity of animals reveals a remarkable range of performance. This specialization depends both on variation in the chemical composition of the cells and on variation in the arrangement and dimensions of the components of the cells. Much of the previous research on this topic has been focused on vertebrate muscle, in which muscle fiber specialization occurs primarily through variation in chemical composition. Little research has been done, however, on muscle specialization in invertebrates, in spite of the fact that a much greater range of striated muscle structure and performance is observed in these animals. The muscle cells to be studied in this investigation are the obliquely striated cells of the arms and the cross striated cells of the tentacles of the squid Loligo pealei. Previous research has shown remarkable differences in the ultrastructure of the two cell types and the physiological implications of these differences have been hypothesized, yet the actual physiological performance of these cells has not been studied. Recent studies also suggest that the cross striated muscle cells of the tentacle are derived, both through ontogeny and phylogeny, from an obliquely striated muscle fiber type. This study will offer the opportunity to explore and to document the physiological implications of the structural specializations of the cross striated fibers. This will be the first measurement of the basic physiological parameters of the two muscle types. These data will be used to test and refine a forward-dynamics model of the tentacle strike.
