Taxonomic Studies of Ciona intestinalis (L.) and Its Allies

Abstract

The two species of the genus Ciona, C. robusta Hoshino et Tokioka and C. intestinalis (Linne) sensu Hoshino & Tokioka, 1967 from the Japanese waters are consistently distinguishable from each other by several minor but distinct features. On the other hand, the survey of literature and examination of many specimens collected from various localities in different years proved that European waters, the type locality of C. intestinalis, have been inhabited only by a single species indistinguishable morphologically from C. robusta. Thus, robusta should be regarded as a junior synonym of intestinalis. Further, it was also proved that C. intestinalis sensu Hoshino & Tokioka should be referred to C. savignyi Herdman originally collected off Kobe, Japan, during the Challenger Expedition, by reexamination of the type specimen of this species. In addition, brief references are made to other described species of the genus Ciona.