Also found in: Dictionary, Encyclopedia, Wikipedia.
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]
Farlex Partner Medical Dictionary © Farlex 2012
Mesozoaa 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.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005