Biological Sciences
Opisthokonta
Opisthokonta is a major eukaryotic supergroup that includes animals, fungi, and several protist groups. It is characterized by a single posterior flagellum in the motile cells of its members. Opisthokonts are important for their roles in ecology, human health, and biotechnology, and their evolutionary history provides insights into the origins of complex multicellularity and diverse modes of nutrition.
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11 Key excerpts on "Opisthokonta"
eBook - ePubOrganelles, Genomes and Eukaryote Phylogeny
An Evolutionary Synthesis in the Age of Genomics
- Robert P Hirt, David S. Horner(Authors)
- 2004(Publication Date)
- CRC Press(Publisher)
Origin and Evolution of Animals, Fungi and Their Unicellular Allies (Opisthokonta)Emma T.Steenkamp and Sandra L.BaldaufAbstract
The well-established exclusive grouping of animals and fungi (Opisthokonta) has recently been expanded to include a diverse collection of protistan taxa. These single-celled opisthokonts or Choanozoa include choanoflagellates (uniflagellated filter feeders), ichthyosporeans (parasites of aquatic animals), corallochytreans (free-living saprotrophs) and cristidiscoideans (nucleariid and ministeriid amoebae). The exact relationships of the choanozoans to each other and to animals and fungi are unknown, because most studies of these taxa are based on single-gene trees and taxonomically nonoverlapping datasets. From the limited data available, the taxon Choanozoa appears to be paraphyletic. However, to substantiate this and to reconstruct the early evolution of opisthokonts, broad sampling of the basal animal and fungal lineages, various choanozoans and appropriate outgroups (i.e., Amoebozoa and Apusozoa) is required. As with all deep phylogenetic questions, resolving the relationships among multi- and unicellular opisthokonts might be difficult, if not impossible, with single-gene trees. This is possibly because they lack sufficient phylogenetic information or are burdened by too many substitutions at individual sites. Thus, the origin of opisthokonts and their early divergence will most probably only be resolved with the analysis of taxonomically well-represented multisequence datasets.5.1 Introduction
An exclusive grouping of animals and fungi, the Opisthokonta (Cavalier-Smith, 1987), is now well established (e.g., Wainright et al., 1993; Baldauf and Palmer, 1993; Baldauf et al., 2000). Most recently, the group has been expanded to include a diverse collection of protistan taxa, also known as the Choanozoa (Cavalier-Smith, 1998b). The specific relationships of most of these Choanozoa to each other and to animals and fungi are currently unresolved, and much remains to be discovered. To provide a background for studying the evolution of the Opisthokonta, we review the relevant literature on the subject. To achieve this, we first discuss the phylogeny within both animals and fungi, with special reference to their possible protist origins. We then briefly describe the various Choanozoa and our current best guess on their relationships to each other and to the animals and fungi. Given that reconstruction of opisthokont phylogenies will undoubtedly require appropriate outgroups, we also discuss the evolution of two groups of protists, Amoebozoa (Cavalier-Smith, 1998b) and Apusozoa (Cavalier-Smith and Chao, 1995), which are strong candidates for being the sistergroup of opisthokonts.
- Kumar, Har Darshan(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Cannot be resold/distributed. not used for oxidative phosphorylation. These cells are quite common in low-oxygen habitats, such as animals guts. Members of one line, Heterolobosea, have evolved as broad-pseudopod-forming amoebae independently of Amoebozoa, and even include their own group of slime moulds, the acrasids. Another group is the secondary algae, the euglenids. Both protein phylogenies and a complex fusion of pyrimidine synthesis genes suggest that Opisthokonta is most closely related to Amoebozoa. This grouping has been referred to as ‘unikonts’. It appears that the root of eukaryotes falls between unikonts and everything else (see Stechmann and Cavalier-Smith, 2003). Ancestral Eukaryotic Cells Eukaryotic cells are very different from their presumably prokaryotic ancestors. The last common ancestor of living eukaryotes appears to have been a ‘complete’ eukaryotic cell that had a nucleus, endoplasmic reticulum and Golgi apparatus, and that underwent mitosis and meiosis. Its mitochondria were capable of oxidative phosphorylation, amongst other functions. It had a complex eukaryotic cytoskeleton including eukaryotic flagella (most likely a pair of them), and was heterotrophic, consuming food particles by phagocytosis. The only major eukaryotic features that seem to be of later origin are plastids. What we still do not understand is: did living eukaryotes diverge soon after the rapid evolution of the eukaryotic cell, or was this cell assembled gradually, but with modern eukaryotes then replacing all intermediate forms (Simpson and Roger, 2004, 2004a). Opisthokonta Two of the major multicellular kingdoms, Metazoa and Fungi, constitute a monophyletic clade, the opisthokonts, which comprises some unicellular lineages, such as Choanoflagellata, Nucleariidae, Ichthyosporea (also known as the DRIPs or Mesomycetozoea), Ministeria and Corallochytrium (Steenkamp and Baldauf, 2004).
eBook - ePubTaxonomic Guide to Infectious Diseases
Understanding the Biologic Classes of Pathogenic Organisms
- Jules J. Berman(Author)
- 2019(Publication Date)
- Academic Press(Publisher)
The value of the eukaryotic undulipodium as a taxonomic divider is demonstrated in Class Opisthokonta. Class Opisthokonta is a subclass of Class Unikonta that contains Class Choanozoa, Class Animalia, and Class Fungi, among others. The opisthokonts all descend from an organism with its undulipodium extending from the rear (from the Greek “opisthios,” meaning rear and “kontos” meaning pole). The rear-ended undulipodium distinguishes the members of Class Opisthokonta from unikonts that have an undulipodium extending from anterior (pole near nucleus) or lateral (smaller width) edges.Section 4.2 Metamonada
Eukaryota Bikonta (2-flagella) Excavata Metamonada TrichozoaOur greatest responsibility is to be good ancestors. Jonas SalkParabasalidea Trichomonadida Trichomonadidae Trichomonas (genus) Monocercomonadidae Dientamoeba (genus) Fornicata Diplomonadida Hexamitidae Giardia (genus) Discoba Euglenozoa Percolozoa Archaeplastida Chromalveolata Alveolata Apicomplexa Ciliophora (ciliates) Heterokonta Unikonta (1-flagellum) Amoebozoa Opisthokonta Choanozoa Animalia FungiClass Metamonada is a class of anaerobic eukaryotes that lack mitochondria. The first eukaryotes possessed three defining anatomic structures: a nucleus, mitochondria (one or more), and undulipodium (one or more). Evolution can be an intolerant process. Structures that serve no important biological purpose cannot justify the resources required to maintain their continued existence. In particular, mitochondria may be a great way for deriving energy from oxygen, but these complex organelles may have little value when conditions are anaerobic.As we will see again and again throughout this book, phylogenetic traits are seldom lost, without leaving some trace of their heritage. The anaerobic members of Class Metamonada maintain a relict organelle, derived from an ancestral mitochondrium. The relict is usually referred to as a mitosome, though a specific term, hydrogenosome, is used to refer to mitochondrial relicts that use iron-sulfide proteins to yield molecular hydrogen and ATP. Various so-called amitochondriate eukaryotic classes that have lost classic mitochondria have retained mitosomes or hydrogenosomes that form molecular hydrogen: Class Metamonada [6] , Class Amoebozoa [7] , and Class Microsporidia [8]
eBook - PDF- Pamela J. W. Gore(Author)
- 2014(Publication Date)
- Wiley(Publisher)
The Bacteria and Archaea are prokaryotes. Prokaryotes are single-celled organisms with cells that do not have a nucleus (called prokaryotic cells). The Eukaryota (animals, plants, protists, and fungi) have cells with nuclei (called eukaryotic cells). The prokaryotic cells are considered more primitive than eukaryotic cells. Oddly enough, studies of genes and biochemistry suggest that Archaea are more closely related to Eukaryota than to Bacteria, although other aspects of their biochemistry are unique. Many Archaea inhabit extreme environments such as hot springs, geysers, and black smokers on the sea floor, but they also inhabit a wide variety of other environments. Eukaryotes (multicellular organisms, and single-celled organisms with a nucleus) are divided into six supergroups based on genetic similarities and differences. This terminology is new (since about 2003), and most textbooks, biologists, and college faculty are still catching up to the rapid changes in classification. The six eukaryote supergroups are: 1. Rhizaria: foraminifera, radiolaria, and others 2. Chromalveolata: diatoms, dinoflagellates, coccolithophores, and others 3. Opisthokonta: animals, fungi, and others 4. Archaeplastida: plants, green algae, calcareous algae, red algae, and others 5. Amoebozoa: amoebas and slime molds 6. Excavata: some flagellate species (Euglena, Giardia, Trichomonas, Leishmania) The animals (both invertebrates and vertebrates) belong to the supergroup Opisthokonta. The word Opisthokonta means “rear pole,” referring to a flagellum attached to the posterior of the cell (e.g., a sperm cell). Some studies have suggested genetic similarities between some of the supergroups; the Opisthokonta and the Amoebozoa are sometimes combined into the Unikonts. Animals and plants have some characteristics in common, but they also have basic differences. Most plants manufacture their own food by photosynthesis (i.e., they are producers or autotrophs).
eBook - ePubEvolution's Clinical Guidebook
Translating Ancient Genes into Precision Medicine
- Jules J. Berman(Author)
- 2019(Publication Date)
- Academic Press(Publisher)
The stretch of evolution extending from the opisthokonts to the parahoxozoans account for two of the three major classes of multicellular organisms (Class Fungi and Class Metazoa), the third being Class Archiplastidae (plants), which split from the lineage leading to humans back at the bikont division of eukaryotes. In addition, the evolutionary innovations that define the animal kingdom were achieved prior to the appearance of the parahoxozoans, and prior to the Cambrian explosion, in a somewhat vague time frame that may have extended from about 1.5 billion years ago to about 600 million years ago.- Opisthokonta
- Holozoa (1300 mya)
- Filozoa
- Apoikozoa (950 mya)
- Metazoa (760 mya) [14]
- Eumetazoa (Dipoblasts, Histozoa, Epitheliozoa) (635 mya)
- Parahoxozoa
Members of Class Opisthokonta, like all unikonts, have a single undulipodium (commonly but erroneously referred to as a flagellum). The undulipodium of the opisthokonts protrudes from the posterior pole, and serves to propel the organism through water. The undulipodia (one or two in number) of other eukaryotic classes are most often anterior. Although the posterior undulipodium characterizes Class Opisthokonta, the cells of many of the descendant opisthokonts, that have evolved from formerly aquatic organisms (i.e., fungi and animals) lack the undulipodium. However, among the fungi, the aquatic chytrids produce gametes (i.e., fungal spores) that have an undulipodium [17] . As previously indicated, among the animals, the undulipodium is retained in spermatocytes. Because each spermatocyte has a undulipodium, we can infer that the genes for building a undulipodium are retained in animals.In addition to their characteristic posterior undulipodium, members of Class Opisthokonta have the ability to synthesize chitin, a long-chain polysacccharide synthesized throughout Class Fungi and in many but not all members of Class Metazoa (e.g., chitin is not synthesized in mammals). All extant organisms that produce chitin are opisthokonts. Chitin is the opisthokont equivalent of cellulose, another long-chain polysaccharide, which is found in members of Class Plantae. Chytrids, unlike all other known opisthokonts, can synthesize both cellulose and chitin.
- Julius Kreir(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Yet the kingdom Protista is definable by a level of organization (eukary-otic, unicellular), whereas the higher kingdoms are defined by kinds and evolutionary directions of organization on the multicellular-multinucleate level. A workable classification can be based on assigning protist phyla to the plant, animal, and fungus kingdoms (Leedale, 1974). In this case, however, a horizontal and vertical classification, horizontally separating an ancestral base taxon from the several taxa as evolutionary lines de-rived from it as suggested by Simpson (1945), may be preferable to dividing up the intergrading members of the ancestral taxon and assign-ing them to the descendent taxa. The protists as a kingdom have seemed monophyletic, but protist evolution by acquisition of moneran symbionts (Margulis, 1968, 1974a,b) may challenge this assumption and imply reconsideration of protist classification. The protists are a complex of variously interconnected evolutionary lines, of many evolutionary developments in parallel and convergence, and of phyla which have been difficult to delimit and some of which are doubtless polyphyletic. So much has been learned of detailed structure and biochemical characteristics which suggests relationships and permits grouping into phyla that we may hope there is much more understanding of the protists to be gained from further study. The treatment of the protists and protozoans in Table I is intentionally conservative. Once the protists are accepted as a kingdom, the protozoans are almost necessarily 22 R. H. Whittaker divided into a number of phyla. For the most part these phyla correspond to the subphyla and superclasses within the phylum Protozoa shown in Table IV of the chapter by Baker that follows. Thus, Baker's (and many other zoologists') subphyla Sporozoa and Ciliophora become phyla of the same names in Table I. I have preferred to group Baker's subphyla Myxospora and Microspora into a single phylum, Cnidosporidia.
eBook - PDF- Rob Desalle, Bernd Schierwater(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
Chapter 1 Putting Animals in their Place within a Context of Eukaryotic Innovations Danielle Vazquez, 1 Laura Wegener Parfrey 2 and Laura A. Katz 1,2 Animals represent just one of an estimated 70+ lineages of eukaryotes (Patterson 1999), and the bulk of the remaining lineages are microbial. During the past decade, perspectives of the organization of eukaryotic diversity have undergone a major shift to a system that recognizes five or six high-level groupings (Adl et al. 2005, Tekle et al. 2009). While deep nodes on the eukaryotic tree of life remain elusive (reviewed in Parfrey et al. 2006), the position of animals emerging from within microbial lineages has been robustly resolved by several lines of evidence (King 2004). Animals are placed within the supergroup Opisthokonta, along with fungi and numerous microbial relatives (Adl et al. 2005, Steenkamp et al. 2006). In this chapter we place animals in their phylogenetic context by focusing on lineages of eukaryotes defined by one or more ultrastructural identities (i.e., unique combinations of subcellular structures). Many of these clades are marked by major innovations in cell and/or genome structure at their base. We argue that this contrasts with animals, which lack clear innovations at the base of the lineage despite many within (e.g., triploblasty, true gut). We focus on eight exemplar clades: foraminifera, diatoms, ciliates, apicomplexa, dinoflagellates, euglenids, parabasalids 1 Department of Biological Sciences, Smith College, Northampton, MA, USA. 2 Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA, USA. E-mail: [email protected] 4 Key Transitions in Animal Evolution and kinetoplastids. Many of the eukaryotic clades originally defined by morphological and/or ultrastructural characteristics are now grouped into larger clades—the Stramenopiles, Alveolates, and Euglenozoa—that are well-supported in molecular analyses.
eBook - PDF- Fitch, J. Patrick(Authors)
- 2002(Publication Date)
At this point it is essential to introduce the vocabulary needed to discuss living organisms. We have focused the discussion on the topics needed for working in the biotechnology field. Since the 1930s the living world has been divided into two different domains of organisms called eukaryotes and prokaryotes. Eukaryote translates into “true kernel” or “with nucleus.” Prokaryote translates into “without kernel or nucleus.” We will interchange common use and misuse of the Latin roots and conjugations—e.g., the popular term prokaryotes and the proper Latin plural prokarya . Traditionally, after the domains Eukarya and Prokarya, the next levels 4 Chapter 1 of separation of living organisms are kingdoms, followed by phyla, classes, orders, families, genera, species, and strains. The Eukarya include four kingdoms: Protista, Plantae, Fungi, and Animalia. The Protista are single-celled organisms, such as the protozoa. The Plantae are multicellular organisms that manufacture their food, such as ferns and trees. The Fungi are single or multicellular organisms that absorb food from the environment, such as yeasts and molds. The Animalia are multicellular organisms that must capture food and digest it internally, such as dogs, birds, and fish. Eukaryotes are the organisms that most people would observe in their daily routine and include people, animals, plants, and fungi. The presence of a nucleus and other cellular organelles is specific to Eukarya and complicates understanding how these cells work. Prokarya were traditionally defined as the Monera kingdom and included both bacteria and archaebacteria. In the past two decades, Carl Woese of the University of Illinois and others have proposed the archaea as a separate domain of life—distinct from bacteria. Archaea are often extremophiles—living, for instance, in high salt (halophilic archaea) or high temperature (thermophilic archaea) environments.
eBook - ePub- Dwight D. Bowman(Author)
- 2020(Publication Date)
- Saunders(Publisher)
3: Protista
The eukaryotes have been divided now into four large groups: the Archaeplastida (the plants); the Unikonts (animals, fungi, and amoebae); the Excavata (many of the better known flagellate parasites); and the SAR group, that is, the Alveolates, including ciliates, coccidia, the organisms causing toxoplasmosis and equine protozoal myeloencephalitis, and the agents of babesiosis and malaria, and the Rhizaria with no significant parasites of domestic animals (Hampl et al, 2009 ). This chapter will discuss members of the Excavata, the Alveolates, a Stramenopile, and a few Unikonts (true amoebae). This classification scheme makes it difficult to talk in terms of the classical “protozoa” because the protozoa actually were representatives of many unrelated groups, often related to various multicellular forms. However, after one gets past the larger groupings and their new names, information about individual parasites remains unchanged.A vast majority of the eukaryotes are unicellular organisms that are related to other multicellular forms (e.g., malaria being related to the brown algae that compose the giant kelp forests of northern oceans). However, in veterinary medicine, interest is focused on agents that cause disease, and these tend to be unicellular forms. The popular term protist is applied to these eukaryotes with a unicellular level of organization, and it is understood that when cell differentiation occurs in these groups, it is restricted to the purposes of sexual reproduction, motility, alternate vegetative morphology for different habitats (e.g., intestinal lumen vs. liver tissue), and quiescent and resistant transmission stages, such as cysts (Adl et al, 2005
eBook - PDF- Ashok Kumar Bishoyi(Author)
- 2020(Publication Date)
- Delve Publishing(Publisher)
The relative description of different features for the five kingdoms is given in the table 6.1 (Ball & Cherry, 2001; Wang et al., 2004). In order to comprehend the various issues and deliberations influencing the classification system, we have to look at these five kingdom classification Biological Classification 185 in detail. Former classification systems encompassed bacteria, fungi, blue-green algae, ferns, mosses, angiosperms and the gymnosperms under ‘Plants’ kingdom. The feature unifying this whole kingdom was the presence of a cell wall in the cells of these organisms. Consequently, groups having widely different characteristics were placed together. For instance, it brought together the blue-green algae and the prokaryotic bacteria with other groups which were eukaryotic (Pawlowski, 2013). Table 6.1. Features of the Five Kingdoms Characters Five Kingdoms Monera Fungi Protista Plantae Animalia Type of Cell Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic Cell wall Noncellulosic (Polysaccharide + amino acid) Present (without cellulose) Present in few Present (cellulose) Absent Body organization Cellular Multicellular / loose tissue Cellular Tissue/ organ Tissue/organ/ organ system Nuclear membrane Absent Present Present Present Present Mode of nutrition Autotrophic and Hetero-trophic Heterotrophic (Saprophytic/ Parasitic) Autotrophic (Photosyn-thetic) and Hetero-trophic Autotrophic (Photosynthetic) Heterotrophic (Holozoic / Saprophytic etc.) Further, it also grouped together the multicellular organisms and unicellular organisms; for instance, Spirogyra and Chlamydomonas were placed together under algae.
eBook - ePub- Barron's Educational Series, Rene Kratz(Authors)
- 2011(Publication Date)
- Barrons Educational Services(Publisher)
The crustaceans and worms are members of the kingdom Animalia. Even though they are small, these organisms are not typically considered to be microorganisms and so will not be considered here. Kingdom Fungi includes molds, yeasts, and mushrooms. Kingdom Protista is made up of a large and very diverse group of organisms that do not fit into any of the other three eukaryotic kingdoms. As we examine the major groups of eukaryotic microorganisms (Table 12.1), the emphasis will be placed upon representative organisms and those that have medical or economic importance. TABLE 12.1. Significant Features of Selected Groups of Eukaryotic Microorganisms. Protista You are probably aware of the many remarkable animals on planet Earth, from the bald eagle to bizarre deep-sea fish. As strange and wondrous as the animals, the protozoa have just as much power to fascinate on a microscopic level. The term “protozoa” refers rather loosely to those members of the kingdom Protista that are unicellular, lack a cell wall, and are generally not photosynthetic. This includes the fast-swimming ciliates, the blob-like amoebae, the spinning dinoflagellates, and many other unique creatures. Traditionally, the protozoa were seen as distinct from the algae, photosynthetic organisms that range in size from single cells to giant kelp. REMEMBER Protozoa are eukaryotic microbes that are predatory and not photosynthetic. Algae are eukaryotes that are photosynthetic, may be single-celled or multicellular (like seaweeds, for example), but aren’t considered true plants. Protozoa and algae are not taxonomic terms; that is, they do not refer to organisms that are closely related to each other. They date back to the time when all organisms were divided up into two kingdoms: the animals, which moved and ate others, and plants, which did not move and performed photosynthesis
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