Marinomyxa Gen. Nov. Accommodates Gall-Forming Parasites of the Tropical to Subtropical Seagrass GenusHalophilaand Constitutes a Novel Deep-Branching Lineage Within Phytomyxea (Rhizaria: Endomyxa)
Abstrakt
Marine representatives of Phytomyxea (SAR: Rhizaria: Endomyxa), a peculiar class of obligate endobiotic parasites, are a greatly understudied ecological group of protists infecting many algal, diatom, and seagrass species. Very little is known about the actual diversity, ecology, and pathogenic potential of these organisms and their taxonomic treatment in many cases follows outdated morphotaxonomic concepts.
Here we focused on resolving the phylogenetic relations of the phytomyxean parasites of the widespread seagrass genusHalophila. We report the first finding ofPlasmodiophora halophilae, the parasite of ovate-leafHalophilaspecies, after more than 100 years since its original description in 1913.
We provide additional information on its anatomy, morphology, distribution, and host range, together with a phylogenetic evidence that it is congeneric with the recently rediscovered species infecting the invasive seagrassHalophila stipulaceain the Mediterranean Sea. Despite the previously hypothesized affiliation of the latter toTetramyxa, our phylogenetic analyses of the 18S rRNA gene placeTetramyxa parasitica(a parasite of brackish water phanerogams and the type species of the genus) in the freshwater/terrestrial phytomyxean order Plasmodiophorida and reveal that phytomyxids associated withHalophilaspp. form a separate deep-branching clade within the class proposed here asMarinomyxagen. nov.
We further argue thatM. marinainfectingH. stipulaceais most likely a species-specific parasite and implies their comigration through the Suez Canal.