Ultrastructure of spermatozoa in four species of Acoela flatworms and their significance for systematics

Abstract

The ultrastructure of sperms in three Acoela species from Japan (Otocelis rubropunctata, Symsagittifera japonica, Amphiscolops sp.) is described for the first time. New data on the sperm ultrastructure of Archaphanostoma agile from the White Sea are presented. Based on the data, the phylogenetic relationships between the families Isodiametridae, Otocelididae, Sagittiferidae and Convolutidae are revised.