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Placozoa
Placozoa ( ; ) is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by Phagocytosis, engulfment, reproducing by Fission (biology), fission or budding, placozoans are described as "the simplest animals on Earth." Structural and molecular analyses have supported them as among the most basal animals, thus, constituting a primitive metazoan phylum. The first known placozoan, ''Trichoplax adhaerens'', was discovered in 1883 by the German zoologist Franz Eilhard Schulze (1840–1921).F. E. Schulze "''Trichoplax adhaerens'' n. g., n. s.", ''Zoologischer Anzeiger'' (Elsevier, Amsterdam and Jena) 6 (1883), p. 92. Describing the uniqueness, another German, Karl Gottlieb Grell (1912–1994), erected a new phylum, Placozoa, for it in 1971. Remaining a monotypic phylum for over a century, new species began to be added since 2018. So far, three other extant species have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichoplax Adhaerens
''Trichoplax adhaerens'' is one of the four named species in the phylum Placozoa. The others are ''Hoilungia hongkongensis'', ''Polyplacotoma mediterranea'' and ''Cladtertia collaboinventa''. Placozoa is a basal group of multicellular animals, possible relatives of Cnidaria. ''Trichoplax'' are very flat organisms commonly less than 4 mm in diameter, lacking any Organ (anatomy), organs or internal structures. They have two cellular layers: the top epitheloid layer is made of ciliated "cover cells" flattened toward the outside of the organism, and the bottom layer is made up of cylinder cells that possess Cilium, cilia used in locomotion, and gland cells that lack cilia. Between these layers is the fibre syncytium, a liquid-filled cavity strutted open by star-like fibres. ''Trichoplax'' feed by absorbing food particles—mainly microbes—with their underside. They generally Asexual reproduction, reproduce asexually, by Cell division, dividing or budding, but can also Sexual r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trichoplacea
''Trichoplax adhaerens'' is one of the four named species in the phylum Placozoa. The others are '' Hoilungia hongkongensis'', ''Polyplacotoma mediterranea'' and '' Cladtertia collaboinventa''. Placozoa is a basal group of multicellular animals, possible relatives of Cnidaria. ''Trichoplax'' are very flat organisms commonly less than 4 mm in diameter, lacking any organs or internal structures. They have two cellular layers: the top epitheloid layer is made of ciliated "cover cells" flattened toward the outside of the organism, and the bottom layer is made up of cylinder cells that possess cilia used in locomotion, and gland cells that lack cilia. Between these layers is the fibre syncytium, a liquid-filled cavity strutted open by star-like fibres. ''Trichoplax'' feed by absorbing food particles—mainly microbes—with their underside. They generally reproduce asexually, by dividing or budding, but can also reproduce sexually. Though ''Trichoplax'' has a small genome in co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladtertia Collaboinventa
''Cladtertia'' is a genus of placozoan discovered in 2022. The genus contains a single described species, ''Cladtertia collaboinventa'', although several other undescribed lineages are known. Its closest described relative is '' Hoilungia hongkongensis'', with whom it forms the order Hoilungea. ''Cladtertia'' is similar in morphology to most other placozoans, but genetically distinct from them. It has been found in warm tropical waters with low seasonal changes, ranging from 26°N to 25°S, where it occupies a distinct ecological niche compared to other placozoan lineages. Sexual reproduction through cross-fertilization has been observed in a strain of ''Cladtertia''. Etymology The genus name comes from Ancient Greek ''kládos'' (clade) and Latin ''tertius'' (the third), referring to its specimens previously being assigned to placozoan Clade III in literature. Biology ''Cladtertia'' is morphologically indistinguishable under light microscopy from other placozoans in the cla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hoilungia Hongkongensis
''Hoilungia'' is a genus that contains one of the simplest animals and belongs to the phylum Placozoa. Described in 2018, it has only Monotypic taxon, one named species, ''H. hongkongensis'', although there are possible other species. The animal superficially resembles another placozoan, ''Trichoplax adhaerens'', but genetically distinct from it as mitochondrial DNA analysis revealed. ''Hoilungia'' was discovered in brackish water from mangrove swamps in Hong Kong. These organisms are generally found in the biofilm surfaces in tropical and subtropical environments. Phylogenetically, they are placed closest to cnidarians. They are diploblastic animals and are believed to have dorso-ventral polarity along top and bottom body layers. Their body is overtly similar to oral-aboral axis of cnidarians. Discovery ''Trichoplax adhaerens'' was discovered by the German zoologist Franz Eilhard Schulze in 1883. But its identification as to what kind of animal it was (systematic position) was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyplacotomea
''Polyplacotoma mediterranea'' is a species in the phylum Placozoa, only representative of the genus ''Polyplacotoma'', and was discovered in the Mediterranean Sea. They differ greatly from other species of placozoans with regards to their morphology and genetic makeup, and have been ranked in the separate class Polyplacotomia. ''P. mediterranea'' has the smallest mitogenome, the lowest GC content, and the smallest intergenic spacer regions of all placozoans. Their bodily structure consists of elongated polytomous body branches, as well as a maximum size that is greater than 10 mm in length. They have also been observed having a diet of algae. The mitochondrial genome of ''Polyplacotoma mediterranea'' is also very compact and contains overlapping protein and tRNA gene codes. ''P. mediterranea'' exhibits significant genetic differences compared to other placozoans. Ancestral state reconstructions of gene content show that ''P. mediterranea'' does not have 600 orthologs that are f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyplacotoma Mediterranea
''Polyplacotoma mediterranea'' is a species in the phylum Placozoa, only representative of the genus ''Polyplacotoma'', and was discovered in the Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur .... They differ greatly from other species of placozoans with regards to their morphology and genetic makeup, and have been ranked in the separate class Polyplacotomia. ''P. mediterranea'' has the smallest mitogenome, the lowest GC content, and the smallest intergenic spacer regions of all placozoans. Their bodily structure consists of elongated polytomous body branches, as well as a maximum size that is greater than 10 mm in length. They have also been observed having a diet of algae. The mitochondrial genome of ''Polyplacotoma mediterranea'' is also very compact and cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metazoan
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million living animal species have been described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from to . They have complex ecologies and interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology, and the study of animal behaviour is known as ethology. The animal kingdom is divided into five major clades, namely Porifera, Ctenophora, Placozoa, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hoilungidae
Hoilungidae is a placozoan family comprising '' Hoilungia'' and other currently undescribed taxa. Named in 2022, it is believed to be sister to Cladtertiidae, and corresponds to Clades IV, V and VII. Previous studies established these clades on the basis of phylogenomic data. Genus ''Hoilungia'' encompasses members of Clade V, while Clades IV and VII have not been formally described as genera. The latter two are believed to encompass multiple species each, although the 2022 study establishing the structure of the family only mapped a single lineage of each. Previously, a wider definition of ''Hoilungia'' included all three clades, as well as clades III and VI. The latter two have since been assigned to Cladtertiidae and Cladhexea respectively. Phylogeny The following phylogeny follows Eitel et al., 2024, and is based on complete mitochondrial genome Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uniplacotomia
Uniplacotomia is a class of placozoans encompassing the vast majority of the phylum, with the exception of '' Polyplacotoma''. It was established in 2022. It comprises the orders Trichoplacea, Cladhexea and Hoilungea. Their morphology is consistent across the class, resembling the typical '' Trichoplax'' as mostly rounded, flat organisms rather than the polytomous, branching structure exhibited by Polyplacotomia Polyplacotomia is a class of placozoans, to this date only comprising ''Polyplacotoma mediterranea ''Polyplacotoma mediterranea'' is a species in the phylum Placozoa, only representative of the genus ''Polyplacotoma'', and was discovered in t .... Despite a uniform exterior morphology, Uniplacotomia exhibits an important degree of diversity in molecular morphology, with at least two dozen species estimated to exist. References Animal classes Placozoa Parazoa {{animal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
