The sarcomonads () or
class Sarcomonadea are a group of
amoeboid
An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
biciliate protists in the phylum
Cercozoa.
They are characterized by a propensity to move through gliding on their posterior
cilium
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike project ...
or through
filopodia
Filopodia (singular filopodium) are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Within the lamellipodium, actin ribs are known as ''microspikes'', and when they extend beyond the lame ...
,
a lack of scales or external
theca
In biology, a theca (plural thecae) is a sheath or a covering.
Botany
In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a comm ...
, a soft
cell surface without obvious cortical filamentous or membranous skeleton, two
cilia without scales or hairs, tubular
mitochondrial cristae, near-spherical
extrusome Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. There are a variety of different types, probably not homologous, and serving various functions.
Notable extru ...
s, and a microbody (probably a
peroxisome) attached to the nucleus.
History
In 1993
Cavalier-Smith
Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford.
His research has led to disc ...
described the sarcomonads as a subclass known as “Sarcomonadia”, an assemblage of unrelated cercozoans (
thaumatomonads,
proteomyxid
Proteomyxidea is a class of Cercozoa. Although it is known to be paraphyletic, further research is needed before its classification can be improved.
References
External links
Cercozoa classes
{{Cercozoa-stub ...
s,
cercomonad
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
s...) and
excavates (
jakobid
Jakobids are an order of free-living, heterotrophic, flagellar eukaryotes in the supergroup Excavata. They are small (less than 15 μm), and can be found in aerobic and anaerobic environments. The order Jakobida, believed to be monophyletic, cons ...
s), in the now defunct class “Heteromitea”, in the old phylum “
Opalozoa
Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista. Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic sapr ...
”. This subclass was created to lump together
protozoa that have an
anisokont type of zoospore (i.e. two
cilia of different lengths), are non-
theca
In biology, a theca (plural thecae) is a sheath or a covering.
Botany
In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a comm ...
te and have
isodiametric extrusome Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. There are a variety of different types, probably not homologous, and serving various functions.
Notable extru ...
s.
Sarcomonadia was composed of three superorders:
#“Jakobidea” (orders
Jakobida and
Cercomonadida), made up of sarcomonads with a single Golgi
dictyosome
The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ...
;
#“Thaumatomonadidea” (order
Thaumatomonadida), with scales made in vesicles associated with the
mitochondria;
#
Proteomyxidea (orders
Pseudosporida and
Leucodictyida
Granofilosea is a class of cercozoans in the subphylum Filosa.
Three groups that were traditionally considered heliozoans belong here: the Heliomonadida, Desmothoracida and Gymnosphaerida, which were recently grouped into the new class of Gran ...
), made up of sarcomonads with an unusual intranuclear rod of
microfilament
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other pr ...
s unseen in other protists.
Phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
analyses published in 1997 showed close relationships between filose and reticulose
amoebae
An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
and zoo
flagellates such as the sarcomonads, and they were grouped under the provisional phylum
Rhizopoda.
In here, the sarcomonads were grouped as the
class Sarcomonadea inside the subphylum
Monadofilosa, and Sarcomonadea was
emended to exclude the
proteomyxid
Proteomyxidea is a class of Cercozoa. Although it is known to be paraphyletic, further research is needed before its classification can be improved.
References
External links
Cercozoa classes
{{Cercozoa-stub ...
s and
jakobid
Jakobids are an order of free-living, heterotrophic, flagellar eukaryotes in the supergroup Excavata. They are small (less than 15 μm), and can be found in aerobic and anaerobic environments. The order Jakobida, believed to be monophyletic, cons ...
s.
Later, in
Cavalier-Smith
Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford.
His research has led to disc ...
's ''
A revised six-kingdom system of life'' of 1998, the phylum
Cercozoa was created to formally establish this group of protists previously known as
Rhizopoda. This discovery put an end to the taxonomical dichotomy between amoebae and flagellates, since they are phylogenetically intermingled in
Cercozoa.
In 2003 the term Sarcomonadea was
emended again to contain only two orders:
#
Metopiida, comprising the single species ''
Metopion fluens'', but was later moved into a different class;
#
Cercomonadida, the
first current sarcomonad order, comprising the families
Cercomonadidae
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
and
Heteromitidae
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
.
In 2009 the problematic
Heteromitidae
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
were broken apart and rearranged into the
second current sarcomonad order Glissomonadida.
In 2012 the
paracercomonads joined Sarcomonadea, initially as
cercomonad
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
s
and later as the
third current sarcomonad order Paracercomonadida.
At the same time, the superclass
Ventrifilosa was created to comprise Sarcomonadea,
Imbricatea and
Thecofilosea.
That same year, the protist ''
Katabia'' was added to Sarcomonadea but remained ''
incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...
'' within the group.
Classification
The class Sarcomonadea is most closely related to
Imbricatea and
Thecofilosea. Together, they form the superclass
Ventrifilosa in the phylum
Cercozoa. The current classification divides the class into three orders:
paracercomonads (subclass
Paracercomonada),
cercomonad
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
s and
glissomonads (subclass
Pediglissa).
Class
Sarcomonadea
Subclass
Paracercomonada
Order
Paracercomonadida
Family
Paracercomonadidae
Subclass
Pediglissa
Order
Cercomonadida
Family
Cavernomonadidae
Family
Cercomonadidae
Cercomonads are small flagellates, widespread in aqueous habitats and common in soils.
Characteristics
The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...
Order
Glissomonadida
Suborder
Allapsina
Family
Allapsidae
Suborder
Sandonina
Family
Bodomorphidae
Family
Sandonidae
Family
Proleptomonadidae
Suborder
Pansomonadina
Family
Viridiraptoridae
Family
Agitatidae
Family
Acinetactidae
Family
Aurigamonadidae
Sarcomonadea ''incertae sedis''
Family
Katabiidae
References
{{Taxonbar, from=Q21215988
Cercozoa classes