New insights into post-fertilization in Dudresnaya (Gigartinales, Rhodophyta) and Acrosymphyton (Acrosymphytales, Rhodophyta)

Dudresnaya (Dumontiaceae, Gigartinales) and Acrosymphyton (Acrosymphytaceae, Acrosymphytales) are florideophycean genera (Rhodophyta) traditionally described as presenting a typical non-procarpic behaviour. The post-fertilization stages of their corresponding generitypes, D. verticillata and A. purpuriferum, have been described on many occasions. Nevertheless, some recent observations led the authors of this study to look more deeply into the development of the carpogonial and auxiliary fusion cells in the generitypes. Main results include a) description of the carpogonial fusion cell development by secondary connection (via fusion in D. verticillata and via conjunctor cells in A. purpuriferum); b) assessment of the existence, prior to diploidization, of primary auxiliary fusion cells in both species, and the description of their development and also that of the auxiliary fusion cells; and c) observation of occasional procarpic behaviour in both species, with gonimoblast developing from the secondary connecting filament initials in D. verticillata and from the carpogonial fusion complex in A. purpuriferum. The study has increased the understanding of the post-fertilization processes and supports the hypothesis that the procarpic behaviour is secondarily derived from non-procarpic ancestors.