Revision of the genus Acasta Leach (Girripedia: Balanoidea)

The relationship between sponge hosts and barnacles are investigated, and the dependence of the morphology of the barnacles on the skeletons of the sponges is shown. The evolutionary development of this group is analysed. Five genera: Archiacasta, Neoacasta, Euacasta, Acasta and Pectinoacasta , are distinguished from the original genus Acasta on the basis of important morphological characteristics. The new sub-family Acastinae is suggested for these genera. The vertical and horizontal distributions of the species of this sub-family are studied. About 150 sponge samples, containing 26 species of these barnacles, have been examined. Eight new barnacle species have been described already in the Russian Zoological Journal. This article provides illustrations of these, and descriptions with illustrations of a further five new species. This group of sponge-inhabiting barnacles, which is rather interesting in morphological and ecological aspects, has not hitherto been examined thoroughly.