Z-line morphology of functionally diverse insect skeletal muscles

In order to make a comparative analysis of Z-line ultrastructure and function, we considered the data existing on the morphology and fine structure of the Z-line in the skeletal muscles of various insects. As a basic structure in striated muscles, the Z-line is involved in many important and complex functions. Although not completely known, its function in skeletal muscle activity is very important. Previous data show that the Z-line occurs in three basic forms: Unstructured Z, typical of not particularly fast muscles with high shortening capacities; Structured Z, typical of fast synchronous and asynchronous muscles; and Fragmented Z, characteristic of supercontracting muscles. By examining different types of muscles, one can deduce that the different morphological modulations follow the same patterns in each functionally different type. The possible evolutionary importance of the distribution of different Z-line models in insects is also considered.