''Polyplacotoma mediterranea'' is a species in the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

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 (biol ...

, 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 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 ...

. ''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 Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spec ...

that are found within all other analyzed placozoans. It also has 76 uniquely present genes and 600 uniquely missing genes compared to other placozoans. ''P. mediterranea'' has a mitochondrial genome that is just over half the size (~23,000 bp) of ''

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, p ...

'', which is more typical for other

metazoa 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 hol ...

References

Placozoa Monotypic animal genera Animals described in 2019 Parazoa {{animal-stub