Two species of the genus Acinetospora (Ectocarpales, Phaeophyceae) from Japan: A. filamentosa comb. nov and A. asiatica sp nov.

The brown algal genus Acinetospora is characterised by sparsely branched uniseriate filaments, scattered meristematic zones, short laterals (crampons) and scattered reproductive organs. The morphology and life history of the generitype A. crinita have been studied repeatedly, and accounts of the species' highly varied reproductive patterns were assumed to be due to the presence of multiple taxa that were reported under this name. Herein, we attempt to contribute to the taxonomy of the genus by conducting morphological and culture studies on 33 Acinetospora samples collected from Japan. We recognised two Acinetospora species and propose to name them A. filamentosa comb. nov. and A. asiatica sp. nov. These two species are distinguished from A. crinita by the absence of monosporangia and plurilocular acinetosporangia/megasporangia. Acinetospora filamentosa and A. asiatica have similar vegetative morphologies but possess different reproductive patterns. The former forms unilocular sporangia on erect filaments and both unilocular sporangia and plurilocular zoidangia on prostrate filaments, while the latter forms plurilocular zoidangia only on both erect and prostrate filaments. Molecular analyses based on rbcL and cox1 genes supported independence of these species.