Cryptic Cryptophytes—Revision of the Genus Goniomonas

Abstract

Cryptomonad protists are ubiquitously distributed over marine and freshwater habitats. As an exception to the colored cryptomonads, the heterotrophic cryptomonads of the genus Goniomonas have an ancestral phylogenetic position. They lack any kind of chloroplast and most likely represent a basal group to those cryptomonad groups having obtained their chloroplast by secondary endosymbiosis. Earlier studies have shown a deep divergence between freshwater and marine clades of goniomonads that comprise large genetic distances between members within the group and also between the two groups of marine and freshwater taxa. Still, marine and freshwater species carry the same genus name, and to date, only a few species have been described. We therefore restructured goniomonad systematics based not only on a separation of marine and freshwater taxa, but also, taking the large genetic distances into account, on several new genera that are described. Based on morphological as well as phylogenetic data (18S rDNA sequences), this leads to the formation of the freshwater genera Limnogoniomonas n. g., Goniomonas, and Aquagoniomonas n. g. and the marine genera Neptunogoniomonas n. g., Baltigoniomonas n. g., Marigoniomonas n. g., Thalassogoniomonas n. g., Poseidogoniomonas n. g., and Cosmogoniomonas n. g. To give the restructuring process a stable basis, we additionally propose a neotype for Goniomonas truncata.