Abstract

This study reports the first record of the genus Aplanochytrium on the coast of Chile, belonging to the class Labyrinthulomycetes in the kingdom Stramenopila. These marine protists play an essential role in carbon and nitrogen cycles as decomposers in the aquatic ecosystem. Although ecologically significant, their global diversity and distribution must be better understood. Samples were collected from Corral Bay, Valdivia, Chile, and later cultivated and identified through classical taxonomy and molecular analysis. Phylogenetic analysis based on the 18S rRNA sequence showed that Chilean samples were recovered in the Aplanochytrium s.s. lineage. Besides Aplanochytrium kerguelense Bahnweg & Sparrow, 1972, found in Kerguelen, an antarctic island from the Indian Ocean, this report extends the geographic distribution of the genus from Asia and the Northern Hemisphere to South America. This finding enhances our understanding of the diversity and distribution of Labyrinthulomycetes. Additionally, the fatty acid profile of Aplanochytrium revealed a high proportion of docosahexaenoic acid (DHA), accounting for 50% of the total fatty acids, along with the presence of palmitic acid. Astaxanthin, a valuable pigment for biotechnological applications, was also quantified. These results highlight the importance of Labyrinthulomycetes in marine ecosystems and their potential in biotechnology.