Paramoebidium
Paramoebidium is a genus of unicellular, symbiotic eukaryotes that inhabit the digestive tract of immature freshwater arthropod hosts. Paramoebidium is classified in the opisthokont class Mesomycetozoea, and is the sole genus in the family Paramoebidiidae. Prior to 2005, Paramoebidium species were tentatively placed with the fungal group Trichomycetes due to their habitation of arthropod guts, host overlap between various Paramoebidium and fungal trichomycete taxa, and similar vegetative growth form.
Etymology
The prefix "para-", roughly meaning "similar to", refers to the assumed relatedness of Paramoebidium to the genus Amoebidium. Members of both genera may produce motile, amoeba-like dispersal cells during their life cycle. The similarity of life cycle, morphology, and ecology lead to the hypothesis that Amoebidium and Paramoebidium were minimally closely related, and probably sister taxa.Description
Paramoebidium species are unicellular. The vegetative cells have an elongate, hair-like growth form with a secreted, glue-like holdfast at the base that attaches them to the host digestive tract lining. Sexual reproduction is unknown. During asexual reproduction, the entire content of the cell is partitioned into many motile amoeboid cells. The cell wall breaks down and the amoeboid cells are released. These amoeboid cells are termed "dispersal amoebae" because they crawl for a short time before encysting. The cyst expands and forms several spores that are released when mature.Species
There are currently 17 validly described species of Paramoebidium. Several other species were described but are considered invalid due to a lack of descriptive detail and/or illustrations. Species have been described based on the morphological features of the thalli, cysts, and cystospores. Host type is also reported for species, but it is unclear how host specific different Paramoebidum species may be. Thallus shapes range from straight, short, and fat to long and sigmoidal, to branched or coiled. For example, ' have short, coiled, thick thalli and are found in black fly larvae, whereas ' have relatively long thalli that are consistently curved near the base giving them a "candy cane" appearance and are associated mainly with mayfly nymphs but also midge larvae. However, while Paramoebidium species are relatively common among trichomycete collections, description of new species is problematic due to the amount of intra- and interspecific variability of the morphological characters. Furthermore, no species have been obtained in axenic culture, so observations are limited to the individuals present at the time of host dissections and some stages of the life cycle may not be present in the collection.List of species:Paramoebidium angulatum Valle 2014Paramoebidium arcuatum Léger & Duboscq ex Duboscq, Léger & Tuzet 1948Paramoebidium argentinense Mazzucch., López-Lastra & Lichtwardt 2000Paramoebidium avitruviense Valle 2014Paramoebidium bacillare Strongman, Juan Wang & Xu 2010Paramoebidium bibrachium Williams & Lichtwardt 1990Paramoebidium cassidula Strongman & White 2006Paramoebidium chattonii Léger & Duboscq 1929 ex Duboscq, Léger & Tuzet 1948Paramoebidium contortum Valle & Busquets 2018Paramoebidium corpulentum Lichtwardt & Williams 1991Paramoebidium curvum Lichtwardt 1979Paramoebidium digitoideum Ferrington, Lichtwardt & López-Lastra 1999Paramoebidium dispersum Léger & Duboscq ex Duboscq, Léger & Tuzet 1948Paramoebidium eccriniforme Léger & Duboscq ex Duboscq, Léger & Tuzet 1948Paramoebidium ecdyonuridae Valle 2014Paramoebidium fuscum Duboscq, Léger & Tuzet 1948Paramoebidium geniculatum Duboscq, Léger & Tuzet 1948Paramoebidium giganteum Duboscq, Léger & Tuzet 1948Paramoebidium grande Lichtwardt & Arenas 1996Paramoebidium hamatum White 2012Paramoebidium inflexum Léger & Duboscq 1929Paramoebidium laterale Busquets & Valle 2018Paramoebidium papillatum Lichtwardt & Williams 1992Paramoebidium pavillardii Manier 1951Paramoebidium pinguiculum Strongman & White 2019Paramoebidium procloeoni Manier 1951Paramoebidium santanderensis Baron & Guardia Valle 2018Paramoebidium simulii Tuzet & Manier 1955Paramoebidium stipula Strongman & White 2006Paramoebidium thrauli Léger & Duboscq ex Duboscq, Léger & Tuzet 1948Paramoebidium torpediniforme Strongman & White 2019Paramoebidium umbonatum Strongman & White 2008