The timing and pattern of myogenesis varies among anurans that have been studied and the different pat- terns may provide useful phylogenetic information. Specific myogenic markers have been described (Muntz, 1975; Kielbowna, 1981; Boudjelida & Muntz, 1987; Radice et al., 1989) and they can provide infor- mation on evolutionary changes for closely related lineages within a clade. For example, we previously com- pared first appearance of a muscle-specific protein, first twitch of axial muscle, onset of multinucleation within axial myotome, and first heartbeat in two pipid genera (Smetanick et al., 1999). We found that although the timing of myogenesis differed, the sequence of events was the same for these two pipids. The similarities we saw in the two pipids could be due their common lineage, or alternatively, be a result of sharing a life history mode. For example, appearance of muscle twitch prior to multinucleation could be an adaptation for rapid development, an advantage in frogs with free-swimming tadpoles. If so, it might occur in other lineages with free swimming tadpoles regardless of phylogenetic distance.
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