''Paramoebidium'' is a genus of unicellular, symbiotic
eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bact ...
s that inhabit the digestive tract of immature freshwater
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, o ...
hosts (e.g.
black fly
A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. It is related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. Over 2,200 spe ...
larvae,
mayfly
Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the ord ...
and
stonefly
Plecoptera is an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the m ...
nymphs).
[Lichtwardt, R.W., M.J. Cafaro, M.M. White. 2001. The Trichomycetes: Fungal Associates of Arthropods Revised Edition. Published online http://www.nhm.ku.edu/%7Efungi/Monograph/Text/Mono.htm ] ''Paramoebidium'' is classified in the
opisthokont
The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and B ...
class
Mesomycetozoea
The Mesomycetozoea (or DRIP clade, or Ichthyosporea) are a small group of Opisthokonta in Eukaryota (formerly protists), mostly parasites of fish and other animals.
Significance
They are not particularly distinctive morphologically, appearing in ...
(= Ichthyosporea), and is the sole genus in the family Paramoebidiidae. Prior to 2005, ''Paramoebidium'' species were tentatively placed with the fungal group
Trichomycetes
Trichomycetes refers to a group of fungi in the division Zygomycota that grow in the guts of arthropods living in aquatic habitats. The name is obsolete, having not been validly published. Species formerly placed in the Trichomycetes are now plac ...
due to their habitation of arthropod guts, host overlap between various ''Paramoebidium'' and fungal trichomycete taxa, and similar vegetative growth form.
[Moss, S.T., 1979. Commensalism of Trichomycetes. In L. R. Batra, ed. ''Insect-Fungus Symbiosis Nutrition, Mutualism, and Commensalism''. Montclair: Allanheld, Osmun & Co. Publishers, Inc., pp. 175–227.]
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
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
.
Description
''Paramoebidium'' species are unicellular. The vegetative cells (=
thalli
Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...
) 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 (called
cystospores) 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,
P. curvum' have short, coiled, thick thalli and are found in black fly larvae (
Simuliidae
A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. It is related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. Over 2,200 spec ...
), whereas
P. hamatum' have relatively long thalli that are consistently curved near the base giving them a "candy cane" appearance and are associated mainly with mayfly nymphs (Ameletidae and
Baetidae
Baetidae is a family of mayflies with about 1000 described species in 110 genera distributed worldwide. These are among the smallest of mayflies, adults rarely exceeding 10 mm in length excluding the two long slender tails and sometimes much ...
) but also
midge
A midge is any small fly, including species in several families of non-mosquito Nematoceran Diptera. Midges are found (seasonally or otherwise) on practically every land area outside permanently arid deserts and the frigid zones. Some 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 (e.g. dispersal amoebae) may not be present in the collection.
List of species:
* ''Paramoebidium angulatum''
Valle 2014
* ''Paramoebidium arcuatum''
Léger & Duboscq ex Duboscq, Léger & Tuzet 1948
* ''Paramoebidium argentinense''
Mazzucch., López-Lastra & Lichtwardt 2000
* ''Paramoebidium avitruviense''
Valle 2014
* ''Paramoebidium bacillare''
Strongman, Juan Wang & Xu 2010
* ''Paramoebidium bibrachium''
Williams & Lichtwardt 1990
* ''Paramoebidium cassidula''
Strongman & White 2006
* ''Paramoebidium chattonii''
Léger & Duboscq 1929 ex Duboscq, Léger & Tuzet 1948
* ''Paramoebidium contortum''
Valle & Busquets 2018
* ''Paramoebidium corpulentum''
Lichtwardt & Williams 1991
* ''Paramoebidium curvum''
Lichtwardt 1979
* ''Paramoebidium digitoideum''
Ferrington, Lichtwardt & López-Lastra 1999
* ''Paramoebidium dispersum''
Léger & Duboscq ex Duboscq, Léger & Tuzet 1948
* ''Paramoebidium eccriniforme''
Léger & Duboscq ex Duboscq, Léger & Tuzet 1948
* ''Paramoebidium ecdyonuridae''
Valle 2014
* ''Paramoebidium fuscum''
Duboscq, Léger & Tuzet 1948
* ''Paramoebidium geniculatum''
Duboscq, Léger & Tuzet 1948
* ''Paramoebidium giganteum''
Duboscq, Léger & Tuzet 1948
* ''Paramoebidium grande''
Lichtwardt & Arenas 1996
* ''Paramoebidium hamatum''
White 2012
* ''Paramoebidium inflexum''
Léger & Duboscq 1929
* ''Paramoebidium laterale''
Busquets & Valle 2018
* ''Paramoebidium papillatum''
Lichtwardt & Williams 1992
* ''Paramoebidium pavillardii''
Manier 1951
* ''Paramoebidium pinguiculum''
Strongman & White 2019
* ''Paramoebidium procloeoni''
Manier 1951
* ''Paramoebidium santanderensis''
Baron & Guardia Valle 2018
* ''Paramoebidium simulii''
Tuzet & Manier 1955
* ''Paramoebidium stipula''
Strongman & White 2006
* ''Paramoebidium thrauli''
Léger & Duboscq ex Duboscq, Léger & Tuzet 1948
* ''Paramoebidium torpediniforme''
Strongman & White 2019
* ''Paramoebidium umbonatum''
Strongman & White 2008
References
{{Taxonbar, from=Q30592782
Mesomycetozoea
Eukaryote genera