Sperm ultrastructure of a member of the black coral family Aphanipathidae: Rhipidipathes reticulata (Anthozoa, Antipatharia)

Fertile male polyps of three colonies of the black coral Rhipidipathes reticulata (Aphanipathidae) from Togian Islands (Indonesia) have been the source of the sperm investigated at ultrastructural level, in order to compare their organization with that of other members belonging to the family Antipathidae and Myriopathidae. The extension of the studies to a representative of the family Aphanipathidae stresses once more the structural similarity of the male gametes in antipatharians. A sketch of the sperm model reports the similarity and differences in the examined taxa. Among the micro-characters, the cup-like body linked to the pericentriolar apparatus, is exclusive of the antipatharians. Other inclusions concern the more common pro-acrosomal vesicles or the acrosomelike structure observed only in Antipathella subpinnata and Myriopathes japonica. Lipid vesicles are occasionally present. A typical inclusion, the electron-dense content of which has a C-shaped configuration, is restricted to Rhipidipathes reticulata and is associated to the cup-like body or to the mitochondrion.