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Centroplasthelida
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] |
Yogsothoth (protist)
''Yogsothoth'' is a genus of centrohelid protists, distinguished by the shape and arrangement of their external scales as well as their colonial life strategy. It was described in November 2018 by Shɨshkin and Zlatogursky, and is part of a newly described clade of centrohelids, determined as such by analysis of molecular data. Etymology The genus name ''Yogsothoth'' is a reference to Yog-Sothoth, a character from H.P. Lovecraft's creative works. The genus was named as such due to its tendency to form colonies of cells with rounded plate-like outer scales and outwardly-radiating axopodia, which is visually similar to Lovecraft's description of Yog-sothoth as a conglomeration of glowing spheres. History of knowledge ''Yogsothoth'' was first described by Shɨshkin and Zlatogursky in November 2018, and was placed within the taxon Panacanthocystidia after identifying that it had too few 18S insertions to be classified under the established taxon of Acanthocystidia. Proposed t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protist
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 paraphyletic grouping of all descendants of the last eukaryotic common ancestor excluding land plants, animals, and fungi. Protists were historically regarded as a separate taxonomic kingdom known as Protista or Protoctista. With the advent of phylogenetic analysis and electron microscopy studies, the use of Protista as a formal taxon was gradually abandoned. In modern classifications, protists are spread across several eukaryotic clades called supergroups, such as Archaeplastida ( photoautotrophs that includes land plants), SAR, Obazoa (which includes fungi and animals), Amoebozoa and " Excavata". Protists represent an extremely large genetic and ecological diversity in all environments, including extreme habitats. Their diversity, larger than for all other eukaryotes, has only been discovered in rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Heliozoa
Heliozoa, commonly known as sun-animalcules, are microbial eukaryotes (protists) with stiff arms (Pseudopodia#Morphology, axopodia) radiating from their spherical bodies, which are responsible for their common name. The axopodia are microtubule-supported projections from the amoeboid cell body, and are variously used for capturing food, sensation, movement, and attachment. They are similar to Radiolaria, but they are distinguished from them by lacking central capsules and other complex skeletal elements, although some produce simple scales and spines. They may be found in both freshwater and marine biology, marine environments. Classification Originally the heliozoa were treated together as a formal taxon Heliozoa or Heliozoea, with the rank of class or phylum, but it has been realised that they are polyphyletic, as the various orders show notable differences and are no longer believed to be descended from a single common ancestor. Instead, "heliozoa" is regarded as a descriptive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2023 Centrohelid
3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies. Evolution of the Arabic digit The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically. However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a with an additional stroke at the bottom: ३. The Indian digits spread to the Caliphate in the 9th c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagellum
A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates. A microorganism may have from one to many flagella. A gram-negative bacterium '' Helicobacter pylori'', for example, uses its flagella to propel itself through the stomach to reach the mucous lining where it may colonise the epithelium and potentially cause gastritis, and ulcers – a risk factor for stomach cancer. In some swarming bacteria, the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell. Across the three domains of Bacteria, Archaea, and Eukaryota, the flagellum has a different structure, protein composition, and mechanism of propulsion but shares the same function of providing motility. The Latin word means " whip" to describe its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhizaria
The Rhizaria are a diverse and species-rich clade of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus '' Paulinella'' in the phylum Cercozoa, they are all non-photosynthetic, but many Foraminifera and Radiolaria have a symbiotic relationship with unicellular algae. A multicellular form, ''Guttulinopsis vulgaris'', a cellular slime mold, has been described. This group was used by Cavalier-Smith in 2002, although the term "Rhizaria" had been long used for clades within the currently recognized taxon. Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters ( synapomorphies), but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods. In the absence of an apomorphy, the group is ill-defined, and its composition has been very fluid. Some Rhizaria possess mineral exoskeletons ( thecae or loricas), which are in diffe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raphidiophrys Contractilis
''Raphidiophrys contractilis'' is a species of freshwater centrohelid. Discovery This species was first isolated from a brackish pond in Shukkeien Garden, Naka-ku, Hiroshima City, Japan. Description ''Raphidiophrys contractilis'' is a spherical organism measuring between 7 and 19 μm in diameter and has several axopodia measuring between 60 and 110 μm. The axopodia are sustained by a set of microtubules arranged in a complex of hexagons and triangles. The cell body is coated by a thin layer of small scales composed of silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f .... These scales are oblong, with curved edges and with the surface always facing the cell body. Feeding behavior ''Raphidiophrys contractilis'' preys on other protists, such as flagellates and ciliat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptomonad
The cryptomonads (or cryptophytes) are a superclass of algae, most of which have plastids. They are traditionally considered a division of algae among phycologists, under the name of Cryptophyta. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella. Some may exhibit mixotrophy. They are classified as superclass Cryptomonada, which is divided into two classes: heterotrophic Goniomonadea and phototrophic Cryptophyceae. The two groups are united under three shared morphological characteristics: presence of a periplast, ejectisomes with secondary scroll, and mitochondrial cristae with flat tubules. Genetic studies as early as 1994 also supported the hypothesis that ''Goniomonas'' was sister to Cryptophyceae. A study in 2018 found strong evidence that the common ancestor of Crypto ... [...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] |
