Many cyanobacterial morphospecies with hemispherical cells have been assigned to the genus Chroococcus, but increasingly genetic information has shown that the genus is polyphyletic. Here we describe two new genera based on two new species, Inacoccus gen. nov. based on Inacoccus carmineus sp. nov. and Cryptococcum gen. nov. based on Cryptococcum brasiliense sp. nov. Both genera have morphological features typical of the genus Chroococcus and are based on strains isolated from terrestrial habitats of the Brazilian Atlantic Forest. Inacoccus differs from Chroococcus in forming nanocytes and by producing an intensely red-coloured sheath. Cryptococcum is a cryptic genus and two species, C. brasiliense and C. komarkovaum, have been recognized by a molecular approach (16 rRNA and 16S-23S ITS sequences). The 16S rRNA gene sequence phylogeny indicates that these proposed genera form monophyletic clades apart from the Chroococcus sensu stricto cluster. Additionally, the tropical species Chroococcus subviolaceus was studied by molecular methods for the first time. The results confirmed a vast phylogenetic diversity hidden under the simple morphology of Chroococcus morphotypes, and show that terrestrial environments are a promising field of research.

The genus Gayralia has a complex taxonomy, often with morphological and ontogenetic characteristics that overlap with those of other monostromatic green algae, mainly Monostroma. Molecular studies of monostromatic green algae are still rare, especially in Brazil, where G. brasiliensis was described originally. Considering the difficulties in delimiting genera and species based on morphological criteria, we investigated the genus Gayralia through ITS sequencing of field collections in the tropical northeastern region of Brazil. Our 14 newly generated sequences formed a fully supported clade with G. brasiliensis showing low intraspecific divergence (0–0.6%). The distribution of G. brasiliensis in Brazil was expanded to the northeastern Brazilian coast, with the first record for the states of Rio Grande do Norte, Paraíba, Alagoas, and Sergipe. In addition, two sequences from India identified as G. “oxysperma” were grouped in the G. brasiliensis clade, indicating that they correspond to the same genetic species. This finding extends the geographical distribution of G. brasiliensis to India. Our results place Monostroma kuroshiense within the Gayralia clade, which warrants a new combination – Gayralia kuroshiensis (F.Bast) comb. nov.

Com base no levantamento bibliográfico realizado sobre as cianobactérias citadas para o Brasil e para o Estado de São Paulo em particular, além de consulta à lista de espécies da flora brasileira e aos bancos de dados de coleções paulistas, encontramos um total de 460 espécies citadas para o Brasil e 378 para o estado de São Paulo. Considerando que o grupo tem ao redor de 2800 espécies, estes números representam bem menos de 20% das espécies conhecidas. Assim, frente a diversidade de ambientes e habitats existentes nos biomas tropicais/subtropicais, o reduzido número de espécies já conhecidas indica que certamente essa biodiversidade está subestimada e deve ser muito maior do que identificamos até agora.