The Stramenopiles, also called Heterokonts, are a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have been secondarily lost. Stramenopiles represent one of the three major clades in the SAR supergroup, along with Alveolata and Rhizaria.
Excavata is an extensive and diverse but paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains a variety of free-living and symbiotic protists, and includes some important parasites of humans such as Giardia and Trichomonas. Excavates were formerly considered to be included in the now obsolete Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged. They are considered to be a basal flagellate lineage.
The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates, having a funnel shaped collar of interconnected microvilli at the base of a flagellum. Choanoflagellates are capable of both asexual and sexual reproduction. They have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the collar of microvilli, where these foodstuffs are engulfed. This feeding provides a critical link within the global carbon cycle, linking trophic levels. In addition to their critical ecological roles, choanoflagellates are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. As the closest living relatives of animals, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals.
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 Breviata comprise the larger clade Obazoa.
Amorphea is a taxonomic supergroup that includes the basal Amoebozoa and Obazoa. That latter contains the Opisthokonta, which includes the Fungi, Animals and the Choanomonada, or Choanoflagellates. The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith in 2002.
Telonemia is a phylum of microscopic eukaryotes commonly known as telonemids. They are unicellular free-living flagellates with a unique combination of cell structures, including a highly complex cytoskeleton unseen in other eukaryotes.
A protist or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a polyphyletic grouping of several independent clades that evolved from the last eukaryotic common ancestor.
The Urmetazoan is the hypothetical last common ancestor of all animals, or metazoans. It is universally accepted to be a multicellular heterotroph — with the novelties of a germline and oogamy, an extracellular matrix (ECM) and basement membrane, cell-cell and cell-ECM adhesions and signaling pathways, collagen IV and fibrillar collagen, different cell types, spatial regulation and a complex developmental plan, and relegated unicellular stages.
Malawimonas is genus of unicellular, heterotrophic flagellates with uncertain phylogenetic affinities. They have variably being assigned to Excavata and Loukozoa. Recent studies suggest they may be closely related to the Podiata.
Holozoa is a clade of organisms that includes animals and their closest single-celled relatives, but excludes fungi and all other organisms. Together they amount to more than 1.5 million species of purely heterotrophic organisms, including around 300 unicellular species. It consists of various subgroups, namely Metazoa and the protists Choanoflagellata, Filasterea, Pluriformea and Ichthyosporea. Along with fungi and some other groups, Holozoa is part of the Opisthokonta, a supergroup of eukaryotes. Choanofila was previously used as the name for a group similar in composition to Holozoa, but its usage is discouraged now because it excludes animals and is therefore paraphyletic.
The apusomonads are a group of protozoan zooflagellates that glide on surfaces, and mostly consume prokaryotes. They are of particular evolutionary interest because they appear to be the sister group to the Opisthokonts, the clade that includes both animals and fungi. Together with the Breviatea, these form the Obazoa clade.
The eukaryotes constitute the domain of Eukarya or Eukaryota, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes: the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes.
Abeoforma whisleri is a single-celled eukaryote that belongs to the Ichthyosporea clade, a group of protists closely related to animals.
Pirum gemmata is a unicellular eukaryote that belongs to the Ichthyosporea clade, a group of protists closely related to animals. P. gemmata was isolated from the gut contents of a marine invertebrate, specifically the detritivorous peanut worm Phascolosoma agassizii.
Sphaeroforma arctica, is a unicellular eukaryote with a pivotal position in the tree of life. It was first isolated from the arctic marine amphipod Gammarus setosus. Like other Ichthyosporeans such as Creolimax and Abeoforma, Sphaeroforma arctica are spherical cells characterized with their capacity to grow into multi-nucleated coenocytes. However, a unique feature of S. arctica, is that no obvious budding, hyphal, amoeboid, sporal or flagellated growth stages have been observed in laboratory growth conditions.
Mantamonads are a group of free-living heterotrophic flagellates that move primarily by gliding on surfaces. They are classified as one genus Mantamonas in the monotypic family Mantamonadidae, order Mantamonadida and class Glissodiscea. Previously, they were classified in Apusozoa as sister of the Apusmonadida on the basis of rRNA analyses. However, mantamonads are currently placed in CRuMs on the basis of phylogenomic analyses that identify their closest relatives as the Diphylleida and Rigifilida.
Colponema is a genus of single-celled flagellates that feed on eukaryotes in aquatic environments and soil. The genus contains 6 known species and has not been thoroughly studied. Colponema has two flagella which originate just below the anterior end of the cell. One extends forwards and the other runs through a deep groove in the surface and extends backwards. Colponema is a predator that feeds on smaller flagellates using its ventral groove. Like many other alveolates, they possess trichocysts, tubular mitochondrial cristae, and alveoli. It has been recently proposed that Colponema may be the sister group to all other alveolates. The genus could help us understand the origin of alveolates and shed light on features that are ancestral to all eukaryotes.
Marine protists are defined by their habitat as protists that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Life originated as marine single-celled prokaryotes and later evolved into more complex eukaryotes. Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly single-celled and microscopic. The term protist came into use historically as a term of convenience for eukaryotes that cannot be strictly classified as plants, animals or fungi. They are not a part of modern cladistics because they are paraphyletic.
Syssomonas is a monotypic genus of unicellular flagellated protists containing the species Syssomonas multiformis. It is a member of Pluriformea inside the lineage of Holozoa, a clade containing animals and their closest protistan relatives. It lives in freshwater habitats. It has a complex life cycle that includes unicellular amoeboid and flagellated phases, as well as multicellular aggregates, depending on the growth medium and nutritional state.
Colponemids are free-living alveolates, unicellular flagellates related to dinoflagellates, apicomplexans and ciliates. They are predators of other small eukaryotes, found in freshwater, marine and soil environments. They do not form a solid clade, but a sparse group of deep-branching alveolate lineages.
