Everything about The Cercozoa totally explained
The
Cercozoa are a group of
protists, including most
amoeboids and
flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there's never a true
cytostome or mouth as found in many other protozoa. They show a variety of forms and have proven difficult to define in terms of structural characteristics, although their unity is strongly supported by genetic studies. Cercozoa are closely related to
Foraminifera and
Radiolaria, amoeboids that usually have complex shells, and together with them form a supergroup called the
Rhizaria.
The best-known Cercozoa are the
euglyphids, filose amoebae with shells of siliceous scales or plates, which are commonly found in soils, nutrient-rich waters, and on aquatic plants. Some other filose amoebae produce organic shells, including the
tectofilosids and
Gromia. They were formerly classified with the euglyphids as the Testaceafilosia. This group isn't monophyletic, but nearly all studied members fall in or near the Cercozoa, related to similarly shelled flagellates.
Another important group placed here are the
chlorarachniophytes, strange amoebae that form a reticulating net. They are set apart by the presence of
chloroplasts, which apparently developed from an ingested
green alga. They are bound by four membranes and still possess a vestigial nucleus, called a nucleomorph. As such, they've been of great interest to researchers studying the endosymbiotic origins of organelles.
Other notable cercozoans include the
cercomonads, which are common soil flagellates, and the
Phaeodarea, marine protozoa that were previously considered
radiolarians. In addition, three groups that are traditionally considered
heliozoans belong here: the
dimorphids,
desmothoracids, and
gymnosphaerids. The exact composition and classification of the Cercozoa are still being worked out. A general scheme is:
In addition two groups of parasites, the
Phytomyxea and
Ascetosporea, and the shelled amoeba
Gromia may be basal Cercozoa, although some trees place them closer to the Foraminifera. The
spongomonads have been included here, but more recently have been considered
Amoebozoa. Some other small groups of protozoans are considered Cercozoa but are of uncertain placement, and it's likely many obscure genera will turn out to be cercozoans with further study.
Further Information
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