Spermatogenesis ultrastructure was studied in a simultaneous hermaphrodite population of the solitary coral Balanophyllia europaea. In this species, spermatogenesis takes place in spermatocysts located within gametogenetic mesenteries surrounded by a bilayered boundary. Spermatogonia and spermatocytes are large flagellate cells, densely packed at the outermost edges of the spermatocyst. Spermatids and sperm are loosely distributed near the centre of the spermatocyst. The cytoplasm of spermatogonia and primary spermatocytes often contains short lengths of free axonemes, probably derived from the reabsorption of a primitive flagellum. Maturing spermatids either contain long intracytoplasmic axonemes, that may be stages of the tail synthesis, or have a flagellum. The morphological features of the sperm of this hermaphroditic scleractinian, very similar to those observed in the sperm of gonochoric taxa, support the hypothesis that the hermaphroditism of this population is an adaptive condition.

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Migrating primordial germ cells of Rana dalmatina embryos were labelled by Dolichos biflorus agglutinin. Confocal microscopy analysis demonstrates the nuclear localisation of the labelling. The glycoconjugate is expressed by primordial germ cells throughout the entire migration process, but it is no longer detectable in late intragonadal primordial germ cells. These data suggest that the a-N-acetylgalactosamine-containing glycoconjugates in the nucleus of primordial germ cells may play a functional role in primordial germ cells protection against differentiation during the migration process. The temporal correlation between disappearance of nuclear Dolichos biflorus agglutinin positivity and colonisation of the gonadal ridges, may be explained by a change in the functional status of primordial germ cells nuclear glycoconjugates in relation with the onset of primordial germ cells differentiation.