When Tominaga made an attempt to establish the monophyly of some lower percoids with an emphasis on the fishes considered related to Shuettea, he found some percoids share a posteriorly extended swimbladder. His preliminary survey of limited representatives of percoids suggested that the posterior extension of the swimbladder could be a synapomorphy for some percoid families. Because the suborder Percoidei is too large to be surveyed by only one ichthyologist, Sakamoto and Matsuura subsequently joined forces with him to study the swimbladder of percoid fishes. In our study on percoids, several groups were found to have a posteriorly extended swimbladder, pointing to the possibility of such a structure playing a role in establishing monophyly for some groups. The present study was made, therefore, to review the occurrence or otherwise of a posterior extension of the swimbladder and related structures in percoids.

The posterior extension of the swimbladder into the myotomes of the caudal region is frequently seen in teleosts (Stannius, 1854; de Beaufort, 1909; Dobbin, 1941; Fänge, 1953; Poll, 1969; Whitehead and Blaxter, 1989). Thus, we also take this opportunity to compile literature information about the swimbladder of representatives of teleosts because we believe that the swimbladder holds promise as a source of characters of systematic value. However, we realize that the detailed search of swimbladder characters of teleosts is far beyond the scope of our percoid-oriented study. We hope that our compilation of swimbladder characters will help others to pursue that promise.