The term polar filament may refer to either of two analogous structures used for host invasion by different groups of parasites: Myxozoa (Metazoa)[1] and Microsporidia (Fungi),[2][3] respectively.
^Americus, Benjamin; Lotan, Tamar; Bartholomew, Jerri L.; Atkinson, Stephen D. (2020). "A comparison of the structure and function of nematocysts in free-living and parasitic cnidarians (Myxozoa)". International Journal for Parasitology. 50 (10–11): 763–769. doi:10.1016/j.ijpara.2020.04.012. PMID32707121.
^Frixione, Eugenio; Ruiz, Lourdes; Santillán, Moisés; De Vargas, Lourdes V.; Tejero, José M.; Undeen, Albert H. (1992). "Dynamics of polar filament discharge and sporoplasm expulsion by microsporidian spores". Cytoskeleton. 22 (1): 38–50. doi:10.1002/cm.970220105.