| Zoochlorella | |
|---|---|
Scientific classification  (obsolete) | |
| (unranked): | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Trebouxiophyceae |
| Order: | Chlorellales |
| Family: | Chlorellaceae |
| Genus: | Zoochlorella K.Brandt, 1881, nom. rejic. |
Zoochlorella (pl.: zoochlorellae) is a coloquial term for any green algae that lives symbiotically within the body of an aquatic invertebrate animal or a protozoan. [1]
Zoochlorellae are various genera belonging to the classes Chlorophyceae and Trebouxiophyceae, [1] historically treated as a single genus Zoochlorella due to their similar appearance to the genus Chlorella . [2] However, this genus was found to be polyphyletic through molecular phylogeny, and currently considered nomen rejiciendum . As a consequence, the two species belonging to this obsolete genus have been transferred to different green algal genera. [1]
The analogy between zoochlorellae and chloroplasts was used by the botanist Konstantin Mereschkowski in 1905 to argue about the symbiotic origin of chloroplasts (then called 'chromatophores', a term used for completely different structures today). [3]
Zoochlorellae are responsible for the greenish colour of sea anemone tentacles. Zoochlorellae and zooxanthellae may both be found in the Pacific coast sea anemones Anthopleura elegantissima and Anthopleura xanthogrammica .
Four species of distantly related testate amoebae have independently evolved into obligate mixotrophy through the acquisition of zoochlorellae: Hyalosphenia papilio and Heleopera sphagni , two lobose amoebae belonging to the order Arcellinida within the phylum Amoebozoa; Archerella flavum , a member of the Labyrinthulomycetes in Stramenopiles; and Placocista spinosa , a filose amoeba belonging to the order Euglyphida within the phylum Cercozoa. [4]
Various ciliates present zoochlorellae, such as the genera Paramecium , Stentor , Climacostomum , Coleps and Euplotes . [1]
In the centrohelid Acanthocystis turfacea lives a unique zoochlorella species known as Chlorella heliozoae . [1]
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms which are more formally characterized.
The green algae are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as a sister of the Zygnematophyceae. Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds. There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments, or highly differentiated macroscopic seaweeds.
Labyrinthulomycetes (ICBN) or Labyrinthulea (ICZN) is a class of protists that produce a network of filaments or tubes, which serve as tracks for the cells to glide along and absorb nutrients for them. The two main groups are the labyrinthulids and thraustochytrids. They are mostly marine, commonly found as parasites on algae and seagrasses or as decomposers on dead plant material. They also include some parasites of marine invertebrates and mixotrophic species that live in a symbiotic relationship with zoochlorella.
The aggregating anemone, or clonal anemone, is the most abundant species of sea anemone found on rocky, tide swept shores along the Pacific coast of North America. This cnidarian hosts endosymbiotic algae called zooxanthellae that contribute substantially to primary productivity in the intertidal zone. The aggregating anemone has become a model organism for the study of temperate cnidarian-algal symbioses.
The euglyphids are a prominent group of filose amoebae that produce shells or tests that in most described species is reinforced by siliceous scales, plates, and sometimes spines, but this reinforcement is absent in other species. These elements are created within the cell and then assembled on its surface in a more or less regular arrangement, giving the test a textured appearance. There is a single opening for the long slender pseudopods, which capture food and pull the cell across the substrate.
Difflugia is the largest genus of Arcellinida, one of several groups of Tubulinea within the eukaryote supergroup Amoebozoa. Arcellinida species produce shells or tests from mineral particles or biogenic elements and are thus commonly referred to as testate amoebae or shelled amoebae. Difflugia are particularly common in marshes and other freshwater habitats.
Paramecium bursaria is a species of ciliate found in marine and brackish waters. It has a mutualistic endosymbiotic relationship with green algae called Zoochlorella. About 700 Chlorella cells live inside the protist's cytoplasm and provide it with food, while the Paramecium provides the algae with movement and protection. P. bursaria is 80-150 μm long, with a wide oral groove, two contractile vacuoles, and a single micronucleus as well as a single macronucleus. P. bursaria is the only species of Paramecium that forms symbiotic relationships with algae, and it is often used in biology classrooms both as an example of a protozoan and also as an example of symbiosis.
Selenastraceae is a family of green algae in the order Sphaeropleales. Members of this family are common components of the phytoplankton in freshwater habitats worldwide. A few species have been found in brackish and marine habitats, such as in the Baltic Sea.
Dictyosphaerium is a genus of green algae, in the family Chlorellaceae. It occurs in freshwater habitats around the world and is planktonic.
Micractinium is a genus of green algae in the family Chlorellaceae. Species of the genus Micractinium are common in freshwater habitats. A few species are found as endosymbionts of protozoa, such as Micractinium conductrix and Micractinium tetrahymenae.
Ochrophytes, also known as heterokontophytes or stramenochromes, are a group of algae. They are the photosynthetic stramenopiles, a group of eukaryotes, organisms with a cell nucleus, characterized by the presence of two unequal flagella, one of which has tripartite hairs called mastigonemes. In particular, they are characterized by photosynthetic organelles or plastids enclosed by four membranes, with membrane-bound compartments called thylakoids organized in piles of three, chlorophyll a and c as their photosynthetic pigments, and additional pigments such as β-carotene and xanthophylls. Ochrophytes are one of the most diverse lineages of eukaryotes, containing ecologically important algae such as brown algae and diatoms. They are classified either as phylum Ochrophyta or Heterokontophyta, or as subphylum Ochrophytina within phylum Gyrista. Their plastids are of red algal origin.
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.
Sea anemones are a group of predatory marine invertebrates constituting the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.
Testate amoebae are a polyphyletic group of unicellular amoeboid protists, which differ from naked amoebae in the presence of a test that partially encloses the cell, with an aperture from which the pseudopodia emerge, that provides the amoeba with shelter from predators and environmental conditions.
Anthopleura xanthogrammica, or the giant green anemone, is a species of intertidal sea anemone of the family Actiniidae.
A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs: those with their own chloroplasts, and those with endosymbionts—and those that acquire them through kleptoplasty or through symbiotic associations with prey or enslavement of their organelles.
An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.
Amphitrema is a genus of testate amoeba in the family Amphitremidae. The genus is commonly found in Sphagnum-dominated peatlands. All species of this genus are mixotrophic and harbor unicellular algae belonging to genus Chlorella.
Hyalospheniidae is a family of arcellinid testate amoebae and the sole family of the infraorder Hyalospheniformes. Commonly referred to as "hyalospheniids", these lobose amoebae are characterized by their ability to generate a shell composed of either organic matter or siliceous particles that may be recycled from euglyphid amoebae. They inhabit soil or freshwater habitats, and are abundant on Sphagnum mosses.
Synchroma is a genus of marine stramenopile algae containing two species with amoeboid morphology. They are grouped within the monotypic family Synchromaceae and order Synchromales as part of an independent clade of ochrophytes known as Picophagea or Synchromophyceae.
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