Perkinsids were first described by Norman D. Levine in 1978, as the classPerkinsea withinAlveolata. Levine only included onegenus,Perkinsus, described in the same publication.[1] Later, the same author treated this group as classPerkinsasida within the phylumApicomplexa, suggesting thatPerkinsus is the most primitive apicomplexan.[10] However, this placement was controversial, and was later disproven byphylogenetic analyses that proved more evolutionary proximity todinoflagellates than to apicomplexans.[11]
In 1999, with the discovery ofParvilucifera, biologists Fredrik Norén andØjvind Moestrup separated the class Perkinsea into a new phylumPerkinsozoa, within theAlveolata, to accommodate these two genera.[2] In 2002 a third genus was described,Cryptophagus (now renamedRastrimonas), but it was nevergenetically sequenced, which makes its phylogenetic position uncertain.[12]
In 2014 a new class was added to the phylum, known asSquirmidea.[13] However, phylogenetic analyses later demonstrated that squirmids are more closely related to the clade unitingApicomplexa andColpodellida than to dinoflagellates and perkinsids, and its status as a class of Perkinsozoa was rejected, making Perkinsea the only remaining class.[14][15]
As of 2023, the order-level classification of perkinsids remains ambiguous, and orders are very sparsely used. The familiesPararosariidae andParviluciferaceae have no assigned parent order,[4][5] although one author,Thomas Cavalier-Smith, previously placedParvilucifera within the orderRastrimonadida, along withRastrimonas.[17] This has not been supported by any other author, and both Rastrimonadida andRastrimonas are omitted from current classifications for lacking molecular data.[12] Similarly, the genusAcrocoelus, assigned directly to the orderAcrocoelida without a family,[17] is also excluded due to the absence of molecular data.[18] The genusMaranthos, althoughgenetically sequenced, is not assigned to any family or order.[19] The remaining groups,Perkinsidae andXcellidae, are only sometimes assigned to order Perkinsida,[20][21] while in other instances their parent taxon is directly Perkinsea.[6][22] Taxonomic ranks (i.e. families, orders, classes...) are mostly omitted in favour of using onlyclades.[18] Shown below is the commonly accepted scheme, omitting order-level taxa:
Simplified cladogram of Perkinsea based on 2021-2023 phylogenetic analyses.[19][5][20]Environmental DNA clades are omitted, with the exception of clade 'NAG01' which groups possible infectious agents of tadpoles.[5]
As mentioned above, two genera have uncertain placement because they have never been genetically sequenced, but they have been assigned to Perkinsea on the basis of theirmorphology:[13]
^abcdNorman D. Levine (1978). "Perkinsus gen. n. and Other New Taxa in the Protozoan Phylum Apicomplexa".The Journal of Parasitology.64 (3): 549.doi:10.2307/3279807.JSTOR3279807.
^abcdNorén, Fredrik; Moestrup, Øjvind; Rehnstam-Holm, Ann-Sofi (October 1999). "Parvilucifera infectans Norén et Moestrup gen. et sp. nov. (Perkinsozoa phylum nov.): a parasitic flagellate capable of killing toxic microalgae".European Journal of Protistology.35 (3):233–254.doi:10.1016/S0932-4739(99)80001-7.
^Agostina V. Marano; Carmen L.A. Pires-Zottarelli; José I. de Souza; Sally L. Glocking; Eduardo Leaño; Claire M.M. Gachon; Martina Strittmatter; Frank H. Gleason (2012). "Chapter 11: Hyphochytriomycota, Oomycota and Perkinsozoa (Super-group Chromalveolata)". In E.B. Gareth Jones; Ka-Lai Pang (eds.).Marine Fungi and Fungal-like Organisms. Göttingen: De Gruyter. pp. 167–214.doi:10.1515/9783110264067.167.ISBN978-3-11-026406-7.
^abIsabel Fernández; Fernando Pardos; Jesús Benito; Nina Larissa Arroyo (1999). "Acrocoelus glossobalani gen. nov. et sp. nov., a protistan flagellate from the gut of the enteropneustGlossabalanus minutus".European Journal of Protistology.35 (1):55–65.doi:10.1016/S0932-4739(99)80022-4.
^Mangot, Jean-François; Debroas, Didier; Domaizon, Isabelle (16 May 2010). "Perkinsozoa, a well-known marine protozoan flagellate parasite group, newly identified in lacustrine systems: a review".Hydrobiologia.659 (1):37–48.doi:10.1007/s10750-010-0268-x.S2CID36522615.
^C. Louise Goggin; Stephen C. Barker (1993). "Phylogenetic position of the genusPerkinsus (Protista, Apicomplexa) based on small subunit ribosomal RNA".Molecular and Biochemical Parasitology.60 (1):65–70.doi:10.1016/0166-6851(93)90029-w.PMID8366895.
^abcClive W. Evans; Selina Patel; Nicholas J. Matzke; Craig D. Millar (28 April 2023). "Cryoxcellia borchgrevinki gen. nov., sp. nov., a new parasitic X‑cell species in an Antarctic nototheniid fish, the bald notothen Trematomus borchgrevinki".Polar Biology.46:513–521.doi:10.1007/S00300-023-03132-W.ISSN0722-4060.WikidataQ124515389.
^Brugerolle, G. (2003). "Apicomplexan parasiteCryptophagus renamedRastrimonas gen. nov".European Journal of Protistology.39 (1): 101.doi:10.1078/0932-4739-00910.
