From Argentine Abyssal Plain to farmed turbot in Spain: A ubiquitous amoeba species Vannella robusta sp. nov. (Amoebozoa, Vannellida)

A strain with the characters of the genus Vannella was isolated from the water layer immediately above the deep-sea sediment collected in the south-western Atlantic Ocean, ca. 4.6 km deep. Small-subunit ribosomal RNA (SSU rRNA) and cytochrome c oxidase (Cox1) gene phylogenetic analyses showed that the new strain branches within the clade of previously isolated unnamed Vannella strains from different marine fish and invertebrate hosts. Although the SSU rRNA gene sequences of these strains show variability within 2% of all nucleotide positions without any regular pattern, the available Cox1 gene sequences from within this clade are identical. Given the morphological homogeneity of the revealed clade, all of its strains can be assigned under the same species name, and the variation of their SSU rRNA is comparable to its intragenomic variation, as shown by molecular cloning of the PCR amplicons. High variability of the SSU rRNA gene sequences within and between independently isolated morphologically identical strains in combination with highly conserved Cox1 gene sequences may be a feature in some clades of Vannella, but is not a general rule for this genus, as SSU rRNA genes conserved between different morphospecies occur in several other clades within Vannella.