Pirsoniales
order of fungi
Pirsoniales (in the botanical code, Pirsoniida in the zoological code) is an order of marine flagellated protists. It consists of six genera and a single family Pirsoniaceae.
Description
Most genera of Pirsoniales are free-living single-celled predators with two flagella. The best studied genus, Pirsonia, is a parasitoid of diatoms with a unique life cycle, where cells differentiate into an intracellular feeding portion, known as the trophosome, and an external generative part, known as the auxosome.
Taxonomy
The first Pirsoniales genus, Pirsonia, was discovered and described in 1990 from parasitic flagellates infecting marine diatoms. Its taxonomic position was left undertermined, as its structure and the differentiation into trophosome and auxosome was unique. After the description of its type species, another six species were added, and electron microscopy observations showed the flagellates have stramenopile flagella with tripartite hair-like mastigonemes. However, because of certain differences with the typical stramenopile organization of the flagellar root, the authors waited for genetic analysis to firmly determine their affinity to stramenopiles.
The first molecular phylogenetic analysis including species of Pirsonia was published in 2004. With the exception of P. mucosa (now Pseudopirsonia, a cercozoan), the genus was firmly placed among stramenopiles, near the hyphochytrids despite the lack of morphological similarity.
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This entry incorporates text from “Pirsoniales” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.