An increasing number of cryptic and pseudo-cryptic species have been found within many newly described diatom species. To resolve the phylogenetic relationships of the genus Pseudo-nitzschia, molecular markers are being widely used in combination (or separately) with different morphological characters. Sequence analysis of ribosomal DNA markers (18S, ITS and 28S) and morphological analyses of Pseudo-nitzschia manniistrain (CIM_D-4), isolated from the Telašćica Bay (Adriatic Sea), differentiate it from all other currently reported strains of this species.