Amoebidiaceae
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Amoebidiidae is a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of single-celled
eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
s, previously thought to be
zygomycete Zygomycota, or zygote fungi, is a former division or phylum of the kingdom Fungi. The members are now part of two phyla: the Mucoromycota and Zoopagomycota. Approximately 1060 species are known. They are mostly terrestrial in habitat, living i ...
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
belonging to the clas
Trichomycetes
but molecular phylogenetic analysesBenny, G. L., and O'Donnell, K. 2000. ''Amoebidium parasiticum'' is a protozoan, not a Trichomycete. ''Mycologia'' 92: 1133-1137.Ustinova, I, Krienitz, L., and Huss, V. A. R. 2000. ''Hyaloraphidium curvatum'' is not a green alga, but a lower fungus; ''Amoebidium parasiticum'' is not a fungus, but a member of the DRIPS. ''Protist'' 151: 253-262.Cafaro, M. 2005. Eccrinales (Trichomycetes) are not fungi, but a clade of protists at the early divergence of animals and fungi. Molecular Phylogenetics and Evolution 35: 21-34. place the family with 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 ...
group
Mesomycetozoea The Ichthyosporea (or DRIP clade, or Mesomycetozoea) 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 i ...
Mendoza L, Taylor JW, Ajello L (October 2002)
"The class mesomycetozoea: a heterogeneous group of microorganisms at the animal-fungal boundary"
''Annu. Rev. Microbiol''. 56: 315–44. doi: 10.1146/annurev.micro.56.012302.160950
(= Ichthyosporea). The family was originally called Amoebidiaceae, and considered the sole family of the fungal order Amoebidiales that included two genera: ''
Amoebidium ''Amoebidium'' is a genus of unicellular, symbiotic eukaryotes in the Opisthokont group Mesomycetozoea, family Amoebidiidae.Reynolds, N.K., M.E. Smith, E.D. Tretter, J. Gause, D. Heeney, M.J. Cafaro, J.F. Smith, S.J. Novak, W.A. Bourland, M.M. ...
'' and ''
Paramoebidium ''Paramoebidium'' is a genus of unicellular, symbiotic eukaryotes that inhabit the digestive tract of immature freshwater arthropod hosts (e.g. black fly larvae, mayfly and stonefly nymphs).Lichtwardt, R.W., M.J. Cafaro, M.M. White. 2001. The Tri ...
''. However, Amoebidiidae is now monogeneric as it was recently emended to include only ''Amoebidium'' (and ''Paramoebidium'' is now the sole genus of the family Paramoebidiidae).Reynolds, N.K., M.E. Smith, E.D. Tretter, J. Gause, D. Heeney, M.J. Cafaro, J.F. Smith, S.J. Novak, W.A. Bourland, M.M. White. 2017. Resolving relationships at the animal-fungal divergence: A molecular phylogenetic study of the protist trichomycetes (Ichthyosporea, Eccrinida). Molecular Phylogenetics and Evolution in press, available online 20Feb.2017. https://dx.doi.org/10.1016/j.ympev.2017.02.007 Species of ''Amoebidium'' are considered obligate
symbionts Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term
midge larvae and water fleas (''
Daphnia ''Daphnia'' is a genus of small planktonic crustaceans, in length. ''Daphnia'' are members of the Order (biology), order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their Saltation (gait), ...
'').Lichtwardt, R.W. 2001. Trichomycetes: fungi in relationship with insects and other arthropods. In: ''Symbiosis''. J. Seckbach, ed. Kluwer Academic Publishers, Netherlands, p. 515-588. However, because ''Amoebidium'' species attach to the
exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...
(exterior) of the host and grow in
axenic culture In biology, axenic (, ) describes the state of a culture in which only a single species, variety, or strain of organism is present and entirely free of all other contaminating organisms. The earliest axenic cultures were of bacteria or unicellul ...
, at least some species may be facultative symbionts.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


Etymology

The "amoeb-" prefix refers to the
amoeba An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by ...
-like dispersal cells that are produced during the life cycle of ''Amoebidium''.Lichtenstein, J. L. 1917a. Sur un ''Amoebidium'' a commensalisme interne du rectum des larves dAnax'' ''imperator'' Leach: ''Amoebidium'' ''fasciculatum'' n. sp. ''Archives de Zoologie Expérimentale et Générale'' 56: 49-62.


Description

As the family is monogeneric, the description follows that of the genus, ''Amoebidium''. ''Amoebidium'' species are single-celled, cigar-shaped or tubular in vegetative growth form (=
thallus Thallus (: 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. A thallus usually names the entir ...
), and attach to the exoskeleton of various freshwater arthropod hosts ( Crustaecea or
Insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
a) by means of a secreted, glue-like basal holdfast. Th
thalli
are coenocytic (i.e. lack divisions within the cell) and are unbranched. Sexual reproduction is unknown

may proceed along two different routes: 1) the entire content of the cell divides into elongated,
uninucleate {{Short pages monitor