Polyplacotoma

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Polyplacotoma
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Placozoa
Class: Polyplacotomia
Order: Polyplacotomea
Tessler et al., 2022
Family: Polyplacotomidae
Tessler et al., 2022
Genus: Polyplacotoma
Osigus et al., 2019
Species:
P. mediterranea
Binomial name
Polyplacotoma mediterranea
Osigus et al., 2019

Polyplacotoma mediterranea is a species in the phylum Placozoa, only representative of the genus Polyplacotoma. [1] 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. [1] Their bodily structure consists of elongated polytomous body branches, as well as a maximum size that is greater than 10 mm in length. The mitochondrial genome of Polyplacotoma mediterranea is also very compact and contains overlapping protein and tRNA gene codes. [2]

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Hoilungia hongkongensis is a species in the phylum Placozoa. The organism appears superficially similar to Trichoplax adhaerens, but genetic analysis of its mitochondrial DNA shows numerous differences. It 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. They feed from lower tissue layer which has various peptidergic gland cells. They feed on algae, bacteria, yeast and other byproducts of biofilms. They reproduce asexually through binary fission and there is also some evidence of sexual reproduction. The Hoilungia hongkongensis genome adds support to the phylogenetic placement of the Placozoa in the animal tree of life

<span class="mw-page-title-main">Uniplacotomia</span> Class of Placozoa

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.

Cladtertia collaboinventa is a species of placozoan discovered in 2022, the only member of the genus Cladtertia, making it the fourth known placozoan species up to date. Its closest described relative is Hoilungia hongkongensis, with whom it forms the order Hoilungea.

Hoilungea is a recently created placozoan order comprising Cladtertia, Hoilungia, and other yet-undescribed species. Named in 2022, it is believed to be sister to Cladhexea, and corresponds to Clades III, IV, V and VII of the literature.

Cladhexea is a recently created placozoan order comprising yet-undescribed species. Named in 2022, it is believed to be sister to Hoilungea, and corresponds to Clade VI of the literature.

Polyplacotomia is a class of placozoans, to this date only comprising Polyplacotoma mediterranea. It was established in 2022. Their morphology is strikingly different from other placozoans in Uniplacotomia, exhibiting a highly ramified, branching structure with multiple amoeboid projections.

Hoilungidae is a recently created placozoan family comprising Hoilungia and other yet-undescribed species. Named in 2022, it is believed to be sister to Cladtertiidae, and corresponds to Clades IV, V and VII of the literature.

References

  1. 1 2 Osigus, Hans-Jürgen; Rolfes, Sarah; Herzog, Rebecca; Kamm, Kai; Schierwater, Bernd (2019-03-04). "Polyplacotoma mediterranea is a new ramified placozoan species". Current Biology. 29 (5): R148–R149. doi: 10.1016/j.cub.2019.01.068 . ISSN   0960-9822. PMID   30836080.
  2. Miyazawa, Hideyuki; Osigus, Hans-Jürgen; Rolfes, Sarah; Kamm, Kai; Schierwater, Bernd; Nakano, Hiroaki (7 January 2021). "Mitochondrial Genome Evolution of Placozoans: Gene Rearrangements and Repeat Expansions". Genome Biology and Evolution. 13 (1): evaa213. doi:10.1093/gbe/evaa213. PMC   7813641 . PMID   3031489.