Laetitia sardoa gen. et sp. nov. a new member of Chlorellales (Trebouxiophyceae, Chlorophyta) isolated from Sardinia Island.

A Sardinian small trebouxiophycean alga, Laetitia sardoa, is described as a novel species and genus. This green alga was collected in an oligotrophic freshwater habitat, and its morphology was investigated. The strain established belongs to the order Chlorellales, of the class Trebouxiophyceae, as inferred from phylogenetic analyses of nuclear-encoded 18S rDNA and chloroplast-encoded ribulose-bisphosphate carboxylase-oxydase gene (rbcL). The analyses supported Laetitia as a distinct lineage, sister to a Marvania clade. The taxonomy of this order has long been problematic due to the lack of distinguishable morphological characteristics. With the characterization of this microalgal strain, we confirmed the necessity of using molecular analyses to determine these cryptic algae. Moreover, our study contributes to the knowledge of the taxonomy and ecology of Chlorellales (Chlorophyta). In addition, the discovery of this new genus in the Ogliastra's Tacchi suggests the potential diversity of this area, which up to now has remained largely unknown, and increases the general knowledge of the microalgal flora of this region.