mesozoan
/ˌmɛsəˈzəʊən
/ /ˌmiːzəˈzəʊən/noun Zoology
A minute worm which is an internal parasite of marine invertebrates. It lacks any internal organs other than reproductive cells, and dissolved nutrients are absorbed directly from the host’s tissues.
- Phyla Orthonectida and Rhombozoa; formerly placed together in the phylum Mesozoa, which was thought to be intermediate between protozoans and metazoans.
- The dicyemid mesozoans, once hypothesized to be non-bilaterian metazoans, have since been shown to possess central class Hox genes indicating that these enigmatic parasites are secondarily simplified bilaterians.
- Hox evidence has also placed dicyemid mesozoans in the clade.
Origin
Early 20th century: from modern Latin Mesozoa (from mesos 'intermediate' + zōion 'animal') + -an.