Definition
A microsporidian is a single-celled parasitic fungus belonging to the phylum Microsporidia. These parasites infect a wide range of animal hosts, including insects, fish, and mammals. Think of them as microscopic invaders that hijack host cells for their own reproduction. They are characterized by their incredibly small spores and unique injection mechanism. They inject their infectious material using a polar tube. Microsporidians can cause diseases, particularly in those with weakened immune systems. They are masters of intracellular parasitism.