Knowra Orthonectida Orthonectida Orthonectida are microscopic, mostly marine parasites with simple bodies and distinct reproductive and ciliated stages. Their life cycles alternate between parasitic forms inside hosts and free-swimming adults.
Plasmodium (Orthonectida) : A multinucleate, amoeboid orthonectid stage that develops within host tissues and produces reproductive cells. This host-dwelling stage gives rise to the reproductive forms that define the orthonectid life cycle.
Dicyemida : A group of microscopic parasites, chiefly of cephalopod kidneys, with simple bodies and complex life cycles. Dicyemids are the closest traditional comparison to Orthonectida among the mesozoan parasites.
Phylogenetics : The study of evolutionary relationships among organisms using shared traits and genetic evidence. Phylogenetic analyses reshaped ideas about where orthonectids belong among animals.
Rhopalura ophiocomae : An orthonectid species reported as a parasite of brittle stars. This species illustrates orthonectid parasitism in echinoderm hosts.
Gametogenesis : The process by which cells develop into mature gametes. Orthonectid plasmodia produce the gametes that form their next generation.
Mesozoa : A historical grouping of simple-bodied animal parasites, especially orthonectids and dicyemids. Orthonectida were long classified within this grouping, whose status has been debated.
Molecular phylogenetics : The inference of evolutionary relationships from DNA, RNA, or protein sequences. Sequence comparisons helped reveal that orthonectid simplicity arose within a more complex animal lineage.
Rhopalura dobrowolskyi : An orthonectid species described from a marine invertebrate host. Its species-level study provides a concrete example of orthonectid anatomy and development.
Ciliated larva : A motile, cilia-bearing juvenile stage in the life cycle of some animals. After fertilization, orthonectid development produces a ciliated stage that can encounter a host.
Annelida : A phylum of segmented worms that includes earthworms, leeches, and many marine worms. Some orthonectids parasitize annelids, making their hosts a key part of their biology.
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