The Mesozoa are minuscule, worm-like parasites of marine invertebrates. Generally, these tiny, elusive creatures consist of a somatoderm (outer layer) of ciliated cells surrounding one or more reproductive cells. A 2017 study recovered Mesozoa as a monophyletic group that emerged in the Lophotrochozoa as sister of the Rouphozoa. [1]

中生动物门 (Mesozoa)所有种类的通称，为一类介于原生动物与 后生动物 之间的微小多细胞动物，似为两者之间「遗失的一环」。形小，长不足1毫米至数毫米。

mesozoan, any of approximately 50 species of small, ciliated, multicellular animals that parasitize other marine invertebrates belonging to the phyla Rhombozoa and Orthonectida. These wormlike organisms lack digestive, respiratory, nervous, and excretory systems; their bodies consist of two layers of as few as 20 to 30 cells each.

Mar 2, 2020 · The mesozoa is an obsolete taxonomic term. For a long time it was a phylum of extremely simple parasitic marine worms, however the phylum has now been divided into two separate phyla. The Dicyemida (parasites of Cephalopoda) and the Orthonectida (parasites of Annelida, Echinodermata, Mollusca and Platyhelminthes).

Phylum Mesozoa The name Mesozoa (mes-o-zo´a) (Gr. mesos, in the middle, + zoon, animal) was coined by an early investigator (van Beneden, 1876) who believed that the group was a “missing link” between protozoa and metazoa. These minute, ciliated, wormlike animals represent an extremely simple level of organization.

Jan 1, 2014 · Members of this phylum represent the simplest of all multicellular animals, and are characterized by tiny, wormlike, parasitic organisms having a single layer of ciliated, epithelial cells that enclose one or more reproductive cells (Stunkard, 1954; McConnaughey, 1963).

Jul 6, 2022 · Dicyemids and orthonectids were traditionally classified in a group called Mesozoa, but their placement in a single clade has been contested and their position (s) within Metazoa is uncertain.

Based on molecular biological studies, which allowed solid comparison of functional, structural as well as of regulatory proteins within the metazoan kingdom in general and especially with respect to Porifera (sponges), it is now well established that Porifera together with other metazoan taxa share a common ancestor (Müller et al., 1994a).

May 21, 2024 · Mesozoa are tiny, simple, worm or blob-like parasites that were once thought of as intermediates between protozoa (motile single-celled organisms) and metazoa (multicellular animals). However, now they are generally thought of as degenerate metazoa, that is, metazoans that descended from more complex animals but were secondarily simplified.

Mesozoans are all tiny organisms that have a very simple structure: the body wall consists of a thin outer membrane that is dotted with large numbers of small cilia. When they beat, they provide a means of locomotion through the host animal's body fluids. The vast bulk of the mesozoan body consists of egg and sperm cells.