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Gymnosphaerid
The gymnosphaerids (or Gymnosphaerida) are a small group of heliozoan protists found in marine environments. They tend to be roughly spherical with radially directed axopods, supported by microtubules in a triangular-hexagonal array arising from an amorphous central granule. Genera There are only three genera, each with a single species: ''Gymnosphaera albida'', ''Hedraiophrys hovassei'', and ''Actinocoryne contractilis''. *''Gymnosphaera albida'' is free-living, usually benthic in shallow water. The cells are round and naked, around 70-100 μm in diameter, and resemble the unrelated '' Actinosphaerium''. The outer cytoplasm, or ectoplasm, forms a distinct layer containing large vesicles. *''Hedraiophrys hovassei'' is larger and lives attached to algae and other objects. The cells have a conical base, and are covered with long siliceous spicules. The ectoplasm is distinct and frothy, and typically contains bacterial and algal endosymbionts. *''Actinocoryne contractilis'' is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centrohelid
The centrohelids or centroheliozoa are a large group of heliozoan protists. They include both mobile and sessile forms, found in freshwater and marine environments, especially at some depth. Characteristics Individuals are unicellular and spherical, usually around 30–80 μm in diameter, and covered with long radial axopods, narrow cellular projections that capture food and allow mobile forms to move about. A few genera have no cell covering, but most have a gelatinous coat holding scales and spines, produced in special deposition vesicles. These may be organic or siliceous and come in various shapes and sizes. For instance, in '' Raphidiophrys'' the coat extends along the bases of the axopods, covering them with curved spicules that give them a pine-treeish look, and in ''Raphidiocystis'' there are both short cup-shaped spicules and long tubular spicules that are only a little shorter than the axopods. Some other common genera include '' Heterophrys'', ''Actinocystis'', and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uninucleate
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Gymnosphaera Albida
''Gymnosphaera'' is a genus of tree ferns in family Cyatheaceae. Taxonomy The genus was originally described by Carl Ludwig Blume in 1828. It was frequently treated by later authors as a synonym of '' Cyathea'' or '' Alsophila''. In the Pteridophyte Phylogeny Group The Pteridophyte Phylogeny Group (PPG) is an informal international group of systematic botanists who collaborate to establish on the classification of pteridophytes ( lycophytes and ferns) that reflects knowledge about plant relationships discove ... classification of 2016 (PPG I), ''Gymnosphaera'' was left as a synonym of ''Alsophila'', as evidence to support its reliable separation was lacking. More recently, Shi-Yong Dong and collaborators proposed the revival and recircumscription of the genus based on additional phylogenetic evidence, an act subsequently accepted by other tree fern workers. Phylogeny , the following species are accepted in the genus as currently circumscribed by the Checklist of Ferns and Lyco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cercozoa
Cercozoa (now synonymised with Filosa) is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by phylogeny, molecular phylogenies of rRNA and actin or Ubiquitin#Polyubiquitin chains, polyubiquitin. They were the first major eukaryotic group to be recognized mainly through phylogeny, molecular phylogenies. They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria. Characteristics The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is 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 b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desmothoracid
Order Desmothoracida, the desmothoracids, are a group of heliozoan protists, usually sessile and found in freshwater environments. The adult is a spherical cell around 10-20 μm in diameter surrounded by a perforated organic lorica, or shell, with many radial pseudopods projecting through the holes to capture food. These are supported by small bundles of microtubules that arise near a point on the nuclear membrane. Unlike other heliozoans, the microtubules are not in any regular geometric array, there does not appear to be a microtubule organizing center, and there is no distinction between the outer and inner cytoplasm. Reproduction takes place by the budding-off of small motile cells, usually with two flagella. Later these are lost, and the pseudopods and lorica are formed. Typically, a single lengthened pseudopod will secrete a hollow stalk that attaches the cell to the substrate. The form of the flagella, the tubular cristae within the mitochondria, and other characters ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crista
A crista (; : cristae) is a fold in the inner mitochondrial membrane, inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on. This aids cellular respiration#Aerobic respiration, aerobic cellular respiration, because the mitochondrion requires oxygen. Cristae are studded with proteins, including ATP synthase and a variety of cytochromes. Background With the discovery of the dual-membrane nature of mitochondria, the pioneers of mitochondrial ultrastructure, ultrastructural research proposed different models for the organization of the mitochondrial inner membrane. Three models proposed were: *Baffle model – According to George Emil Palade, Palade (1953), the mitochondrial inner membrane is convoluted in a baffle-like manner with broad openings towards the intra-cristal space. This model entered most text ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondrion
A mitochondrion () is an organelle found in the cell (biology), cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term ''mitochondrion'', meaning a thread-like granule, was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase popularized by Philip Siekevitz in a 1957 ''Scientific American'' article of the same name. Some cells in some multicellular organisms lack mitochondria (for example, mature mammalian red blood cells). The multicellular animal ''Henneguya zschokkei, Henneguya salminicola'' is known to have retained mitochondrion-related organelles despite a complete loss of their mitochondrial genome. A large number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
