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

Evolution of Green Plants Accompanied Changes in Light-Harvesting Systems

Photosynthetic organisms have various pigments enabling them to adapt to various light environments. Green plants are divided into two groups: streptophytes and chlorophytes. Streptophytes include some freshwater green algae and land plants, while chlorophytes comprise the other freshwater green algae and seawater green algae. The environmental conditions driving the divergence of green plants into these two groups and the changes in photosynthetic properties accompanying their evolution remain unknown. Here, we separated the core antennae of PSI and the peripheral antennae [light-harvesting complexes (LHCs)] in green plants by green-native gel electrophoresis and determined their pigment compositions. Freshwater green algae and land plants have high Chl a/b ratios, with most Chl b existing in LHCs. In contrast, seawater green algae have low Chl a/b ratios. In addition, Chl b exists not only in LHCs but also in PSI core antennae in these organisms, a situation beneficial for survival in deep seawater, where blue-green light is the dominant light source. Finally, low-energy Chl (red Chl) of PSI was detected in freshwater green algae and land plants, but not in seawater green algae. We thus conclude that the different level of Chl b accumulation in core antennae and differences in PSI red Chl between freshwater and seawater green algae are evolutionary adaptations of these algae to their habitats, especially to high-or low-light environments

A Morphological and Molecular Study on the Gracilariaceae (Gracilariales, Rhodophyta) around the Hakata Bay, Northern Kyushu, Japan

Detailed morphological study on the plants of the Gracilariaceae around the Hakata Bay, northern Kyushu, Japan revealed that five species of the family were recognizable in this area. According to the previous description, they were assignable to Gracilaria chorda, G. cuneifolia, G. parvispora, G. textorii and G. vermiculophylla. Of these, only G. chorda was separated from the other four species by its lack of spermatangial cavities and nutrient tubular cells in cystocarps. As rbcL gene sequence analyses and the resultant phylogenetic trees (maximum parsimony, maximum likelihood, Bayesian inference) support this distinction, the four species were retained in the genus Gracilaria while G. chorda was considered to belong to Gracilariopsis, a genus that consists of species with superficial spermatangia and without nutrient tubular cells. In our phylogenetic trees, G. vermiculophylla was recovered as a basal species to all other Gracilaria species, which were positioned in the same evolutionary lineage. Interestingly, our specimens of G. vermiculophylla showed a mixture of spermatangial conceptacles, monocavitied (the verrucosa type) and multicavitied (the polycarvernosa type) on the same blade. However, the multicavitied conceptacle is a major character of other genus Hydropuntia within the Gracilariaceae. Further studies are thus necessary to clarify the relationship among these genera and to establish a better classification system of the family