Mesozoa


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Related to Mesozoa: Parazoa, Metazoa

Mes·o·zo·a

(mez-ō-zō'ă),
A small phylum of about 50 species of parasites of marine invertebrates with complex life cycles. Mesozoa are classified with the Metazoa, but they are regarded by some observers as intermediate between unicellular and multicellular animals; others consider them a degenerate group of flatworms. Mesozoa are divided into two distinct orders, the Orthonectida and Dicyemida; the latter are nephridial parasites of squids, octopods, and cuttlefish.
[meso- + G. zōon, animal]

Mesozoa

a small group of minute work-like organisms parasitic on Mollusca which have a sexual generation (the nematogen) alternating with an asexual generation. The group is sometimes given the status of a subkingdom, characterized by being diploblastic, in that the reproductive cell(s) are surrounded by a layer of somatic cells.
References in periodicals archive ?
the Mesozoa, the Placozoa and various groups of Protozoa"; (11) M.
Although adult morphology varies vastly across the group, many core Lophotrochozoa (including the Mollusca, Annelida [including Vestimentifera, Pogonophora, and Echiura, and possibly Myzostoma, and Sipunculida], Gnathostomulida, Nemertea, dicyemid Mesozoa, Entoprocta, and some Platyhelminthes [including polyclad Turbellaria, Catenulida, and Macrostomida]) exhibit spiral cleavage, a highly conserved pattern of early development.
We have sequenced 18S ribosomal RNA genes (18S rDNA) in two species of the dicyemid mesozoa.