Myxozoan Parasites and their Recent Advancements: A Review

The myxozoans are a large group of microscopic metazoan parasites having multicellular myxospores and polar capsules and these represent around 18% of cnidarian species diversity. These parasites undergo a complex, multicellular development, culminating in the formation of a multicellular myxospore that is resistant to the external environment. Myxozoans have evolved to infect virtually all fish tissues and exhibit a degree of host and tissue specificity. Earlier, myxozoan were considered as a close relatives of cnidarians which includes jellyfish, hydroids, corals and sea anemones and of bilaterians. As their distinct nature became clear through 18S ribosomal (rDNA) sequencing, they were reallocated in the phylum Cnidaria. They utilize annelids as definitive hosts and amphibians, homeotherms (waterfowl and shrews) as intermediate hosts in addition to fish. Fish are the only known intermediate hosts for malacosporeans. This paper is an attempt to review the current status of myxozoans and their recent advancements.