Chromalveolata
Chromalveolata is a supergroup of protists that includes a diverse range of organisms such as brown algae, diatoms, and ciliates. It is characterized by the presence of chlorophyll c and a unique type of flagellar hairs called mastigonemes. This group is of significant interest in evolutionary biology and has important ecological and economic implications due to its members' roles in marine and freshwater ecosystems.
7 Key excerpts on "Chromalveolata"
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)
...They comprise two major groups: the kingdom Chromista (Cavalier-Smith, 1981, 1986, 1989) and the protozoan infrakingdom Alveolata (Cavalier-Smith, 1991a, 1993b). Each has very distinctive cellular properties that differ from those of the three more familiar higher kingdoms and offer difficult but exciting challenges to evolutionary cell biology. Phylogenetically, chromalveolates can be defined as the chromophyte algae (those ancestrally having chloroplasts with chlorophyll c, Christensen, 1989) and all their disparate nonphotosynthetic descendants. As Fungi comprise only four phyla, even including Microsporidia (Cavalier-Smith, 1998, 2000) and plants but five (Cavalier-Smith, 1998), the systematic importance of the seven chromalveolate phyla is considerable. There are 123,000 or more described species (Corliss, 2000), more than half of all protists, and perhaps as many undescribed ones. Table 4.1 summarizes their classification into 47 classes and Figure 4.1 their mutual relationships. Together with the plant kingdom and the protozoan infrakingdoms Excavata and Rhizaria, chromalveolates constitute the most megadiverse eukaryotic clade, the bikonts—the ancestrally biciliate eukaryotes (Figure 4.2). It is beyond the scope of the chapter to illustrate their remarkable structural diversity; intrigued readers should consult Graham and Wilcox (2000) and Lee et al. (2002). Chromists were originally defined (Cavalier-Smith, 1981) as organisms having one or both of two key characters: (1) rigid tubular hairs on at least one of their typically two cilia, and (2) plastids having an additional smooth membrane (now called the periplastid TABLE 4.1 Revised Classification of the 47 Classes of Chromalveolates FIGURE 4.1 Probable phylogenetic relationships of the major chromalveolate clades and their grouping into higher taxa. Groups with at least some photosynthetic members or leucoplasts are underlined...
eBook - ePub- Arun Kumar, Jay Shankar Singh(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
...2008; Achibald 2009). Then a later subsequent endosymbiotic incident invoking the integration of eukaryotic algae into other eukaryotes, led to the development of all other plastids; that existed in Chromalveolata (kelps, dinoflagellates and malaria parasites), Excavata (euglenids) and Rhizaria (chlorarachniophytes) (Archibald 2012, Ball et al. 2011). The super group Archaeaplastida comprises only of the organisms with primary plastids, while secondary and tertiary plastids primarily exist in the members of the Chromalveolata (Cryptophyta, Stramenopiles, Haptophyta, Apicomplexa, Chromerida and certain Dinoflagellata), Excavata (Eugleonophyta) and Rhizaria (Chlorarachniophyta) (Fig. 1.2). The presence of plastid-lacking organisms is more surprising and confusing, it could be possible they never had plastids or lost their plastids. Based on the recent phylogenetic analyses on the host level, the group Stramenopiles is placed together with the Alveolata (includes Chromerida, Apicomplexa and Dinoflagellata) and Rhizaria (includes Chlorarachniophyta that have green-plastids), these groups are collectively abbreviated as SAR. Haptophyta (group Chromalveolata) which is considered as a sister group to the SAR; and Cryptophyta was found to be more close to the group Viridiplantae (Burki et al. 2012), while the Euglenophyta (group Excavata) was distantly related to the above mentioned groups. Based on the phylogenetic analyses on the plastid level, there are evidences of secondary endosymbiotic events from either a Chlorophyta (green lineage) or a Rhodophyta (red lineage), but there are no reports of endosymbiotic events from a Glaucophyta. Chlorophyta, the green lineage undergoes two independent endosymbiotic events, where members of core families UTC (Ulvophyceae,Trebuxiophyceae, Chlorophyceae) and Prasinophyceae family leads to the origin of the Chlorarachniophyta (Rhizaria) and Euglenophyta (Excavata), respectively (Rogers et al. 2007, Turmel et al. 2009)...
eBook - ePub- Simon Baker, Jane Nicklin, Caroline Griffiths(Authors)
- 2011(Publication Date)
- Taylor & Francis(Publisher)
...Chloroplasts in this group are very variable structures; they can be large and single, multiple, ribbon-like or stellate chloroplasts with chlorophylls a and b and carotenoids and they store starch. Chlorophytan cells have a vegetative phase that is haploid, and sexual reproduction occurs when cells are stimulated to produce gametes instead of normal vegetative cells at binary fission. Figure 1. Current taxonomic scheme for the Archaeplastida, Excavata, and Chromalveolata They often possess flagella that have a 9 + 2 microtubule arrangement within them (Section H2). There may be one or two flagella per cell, which may be inserted apically, laterally or posteriorly and trail or girdle the cell. The flagellum can be a single whiplash or it can have hairs and scales. The presence of eyespots near the flagellar insertion point allows the cell to swim towards the light. Movement may be by lateral strokes or by a spiral movement that can push or pull the cell through the water. Table 1. Characteristics of the major monophyletic groups of the Archaeplastida, Excavata, Chromalveolata, and Amoebozoa Group Common name Characteristics Examples Archaeplastida Chlorophyta Green algae Chlorophyll a and b, cellulose cell walls Chlamydomonas Excavata Euglenozoa Flagellate unicells Euglenids Mostly photosynthetic Euglena Kinetoplastids Single large mitochondrion Trypanosoma Fornicata Contain mitosome, axially symmetric cells Giardia Chromalveolata Alveolata Unicellular; sacs (alveolata)below cell surface Pyrrophyta Dinoflagellates Golden brown algae Peridinium Apicomplexa Apical complex aids host cell penetration Plasmodium Ciliophora Ciliates Cilia; macro- and micronucleus Paramecium Stramenopila Motile stages with two unequal flagella, one with hairs Bacillariophyt Diatoms Unicellular, photosynthetic, two silicon-containing frustules Navicula Chrysophytes Golden brown algae Photosynthetic...
eBook - ePub- Britannica Educational Publishing, Kara Rogers(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
...Some evidence suggests that such plugs regulate the intercellular movement of solutes. Ribosomal gene sequence data from studies in molecular biology suggest that the red algae arose along with animal, fungal, and green plant lineages. The green algae are evolutionarily related, but their origins are unclear. The Prasinophyceae, which contains the genus Micromonas, is believed to be one of the most ancient groups of chlorophytes, and some fossil data support this view. The photosynthetic algal dinoflagellates (dinophytes) are of uncertain origin. During the 1960s and ’70s the unusual structure and chemical composition of the nuclear DNA of the dinophytes were interpreted as somewhat primitive features. Some scientists even considered these organisms to be mesokaryotes (intermediate between the prokaryotes and the eukaryotes); however, this view is no longer accepted. Their peculiar structure is considered as a result of evolutionary divergence, perhaps about 300 or 400 million years ago. The dinophytes may be distantly related to the chromophytes (chromists), but ribosomal gene sequence data suggest that their closest living relatives are the ciliated protozoa. It is likely that dinophytes arose from nonphotosynthetic ancestors and that later some species adopted chloroplasts by symbiogenesis and thereby became capable of photosynthesis, although many of these organisms still retain the ability to ingest solid food, similar to protozoa. The origin of chromophytes also remains unknown. Ultrastructural and molecular data suggest that they are in a protistan lineage that diverged from the protozoa and aquatic fungi about 300 to 400 million years ago. At that time, chloroplasts were incorporated, originally as endosymbionts, and since then the many chromophyte groups have been evolving. Fossil, ultrastructural, and ribosomal gene sequence data support this hypothesis. The cryptophytes are an evolutionary enigma...
eBook - ePubMicroalgae
From Future Food to Cellular Factory
- Jöel Fleurence(Author)
- 2021(Publication Date)
- Wiley-ISTE(Publisher)
...The use of molecular markers such as ribosomal DNA or ribosomal RNA has shown that these organisms do not constitute a monophyletic group. Within the eukaryotic phylogenetic tree, red and green algae are grouped in the “green line” group, which includes terrestrial plants (see Figure I.2). Dinoflagellates, microalgae initially grouped in the phylum of Chromophyta and the branch of Pyrrophycophyta (Spector 1984), are now listed within the Alveolobiontes or Alveolates group, which includes protozoa, such as ciliates, or sporozoan, or apicomplexa (Bhattacharya et al. 1992). Diatoms, Haptophyta and Phaeophyceae, are associated with oomycetes (Aritzia et al. 1991) within the group of Heterokonta (Selosse 2006). Haptophyta, whose plastids have an endosym biotic rhodophyta origin and whose main characteristic is the presence of an organelle acting as a flagellum (haptonema) (Sexton and Lomas 2018), were thus isolated from their initial phylum. This new classification shows that the pigment character initially chosen to classify the algae was not a sufficiently relevant criterion to retrace the evolutionary history of the algae. Nevertheless, this criterion is still relevant to distinguish the major botanical groups of algae that are being valorized, whether in the field of biotechnology or in that of human or animal nutrition. 1.1.3. The special case of cyanobacteria (Cyanophyceae) Cyanobacteria have long been considered microalgae and classified as Cyanophyceae or “blue algae” or “blue-green algae”. These organisms belong to the prokaryotic lineage, which is not the case for algae, which are all eukaryotic organisms. Cyanobacteria are the most important group of photosynthetic bacteria. The size of these organisms can vary between 1 μm and 10 μm. Cells can be isolated or form cell colonies of various shapes. In particular, they can produce filamentous excretions or trichomes...
eBook - ePubHandbook of Microbiology
Condensed Edition
- Allen I Laskin(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...A major phyletic gap, therefore, separates red algae (non-flagellated, eukaryotic) + blue-green algae (non-flagellated, prokaryotic) and the flagellates (eukaryotic). A missing link may be Glaucocystis, which has phycobilins, flagella (though functionless), and a chloroplast reminiscent of that in red algae. 2, 3 The eyespot is emerging as a valuable taxonomic character (Table 1). Class 1. Phytamastigophorea (Phytoflagellates) Typically these organisms have chloroplasts; if chloroplasts are lost secondarily, the relationship to pigmented forms is clearly evident. Commonly they have only one or two emergent flagella; ameboid forms are found in some groups. The carotenoids of the various phytoflagellate groups are characteristic; chlorophytes have pigments like those of higher plants; euglenids also have the carotenoids diadinoxanthin and diatoxanthin. For a survey of algal carotenoids, see Reference 4; for details, see Reference 5. Satisfactory agreement between the zoological and botanical classifications of the phytoflagellates has not yet been reached. Order 1. Chrysomonadida A vast group, yellow to brown because of abundant yellow carotenoids of the fucoxanthin series. In common with other brown-pigmented groups of algae (diatoms, phaeophycean seaweeds) and dino- flagellates, they Contain chlorophyll c, which is lacking in the chlorophytes (green algae and higher plants). They usually have one, two, or three flagella. Relations to brown seaweeds and Xanthophycene are briefly reviewed in Reference 6. The group includes the following widely studied species: Ochromonas malhamensis. Phagotrophic and weakly photosynthetic. The only microorganism known to share the pattern of B 12 requirement of higher animals (no response to pseudo B 12 ’s; B 12, i.e., cyanocobalamin, is spared by methionine; propionate oxidation is stimulated by B 12) Table 1 Eyespot Types In Flagellates a Ochromonas danica. Vigorously phagotrophic and photosynthetic...
eBook - ePubThorp and Covich's Freshwater Invertebrates
Ecology and General Biology
- James H. Thorp, D. Christopher Rogers(Authors)
- 2014(Publication Date)
- Academic Press(Publisher)
...These include: (1) the stramenopiles, a group containing organisms as morphologically and functionally dissimilar as chrysomonad flagellates and diatoms; and (2) the alveolates, a group that embraces the dinoflagellates, the ciliates, and a large group of exclusively intracellular parasites (the apicomplexans) (Adl et al., 2012). In the next sections, we focus on the broad morphological–functional groups of free-living protozoa. FIGURE 7.2 A selection from the variety of form and function in ameboid protozoa and slime molds. (a) An actinophryid heliozoon (Actinophrys ; diameter ∼0.1 mm) ingesting a flagellate. (b) A benthic foraminiferan (Rotalia) trapping diatoms and bacteria in its reticulopodial net. (c) A naked ameba (Amoeba) using pseudopodia to trap a flagellate. (d) A polycystine radiolarian (Heliosphaera ; spherical body ∼0.3 mm) with symbiotic dinoflagellates and an entrapped tintinnid ciliate. (e) Polymorphic life cycles of dictyostelid slime molds (e.g., Polysphondylium ; outer circle) and myxomycete slime molds (e.g., Physarum ; inner circle). (f) Testate ameba (Assulina ; ∼0.08 mm) with its prey (an algal cell) caught on a sticky filopodium. Ameboid Protozoa Rhizopod amebae use pseudopodia (cytoplasmic protrusions) for locomotion and feeding. There are two large groups (Figures 7.1 and 7.2): the “naked amebae” (e.g., Acanthamoeba, Vannella, Amoeba, and Vampyrella) and the shelled “testate amebae” (e.g., Arcella, Nebela, and Euglypha). Most rhizopod amebae feed nonselectively by engulfing diatoms and other algae, unicellular and filamentous cyanobacteria, detritus, and bacteria. However, there are notable variants: Vampyrella dissolves a hole in the cell wall of a green alga or desmid and then enters through the hole to digest the cytoplasm of the prey...
