1. A small, parasitic marine animal of the phylum Mesozoa, typically found in the kidneys or reproductive organs of cephalopods and other marine creatures.
Usage: biology; zoology; technical

Examples

• The mesozoan is a simple organism that lives as a parasite inside marine animals.
• Scientists study mesozoans to understand parasitic relationships in ocean ecosystems.
• The mesozoan's body structure is more complex than a virus but simpler than most other animals.
• Mesozoans were once thought to be a separate evolutionary lineage but are now classified differently.
• The mesozoan infects its host without causing obvious harm in many cases.