Gill louse

The gill lice are a genus (Ergasilus) of copepod crustaceans occurring in both the ocean and fresh water. The females are parasitic upon the gills of fishes. This is similar to members of the crustacean subclass Branchiura (fish lice). Being copepods, gill lice have a single median eye on their head. The second antennae are modified into prehensile pincers. Male gill lice are free-living.

Species include :
 * Ergasilus arthrosis L. S. Roberts, 1969
 * Ergasilus auritus Markevich, 1940
 * Ergasilus briani
 * Ergasilus caeruleus C. B. Wilson, 1911
 * Ergasilus celestis J. F. Müller, 1937
 * Ergasilus centrarchidarum Wright, 1882
 * Ergasilus cerastes L. S. Roberts, 1969
 * Ergasilus chautauquaensis Fellows, 1887
 * Ergasilus clupeidarum S. K. Johnson & W. A. Rogers, 1972
 * Ergasilus cotti Kellicott, 1892
 * Ergasilus cyanopictus
 * Ergasilus cyprinaceus W. A. Rogers, 1969
 * Ergasilus elongatus C. B. Wilson, 1916
 * Ergasilus felichthys (Pearse, 1947)
 * Ergasilus fryeri
 * Ergasilus funduli Krøyer, 1863
 * Ergasilus gibbus Von Nordmann, 1832
 * Ergasilus globosus
 * Ergasilus labracis Krøyer, 1863
 * Ergasilus lanceolatus C. B. Wilson, 1916
 * Ergasilus lizae Krøyer, 1863
 * Ergasilus longimanus
 * Ergasilus luciopercarum Henderson, 1926
 * Ergasilus manicatus C. B. Wilson, 1911
 * Ergasilus megaceros C. B. Wilson, 1916
 * Ergasilus mugilis Vogt, 1877
 * Ergasilus myctarothes
 * Ergasilus nerkae L. S. Roberts, 1963
 * Ergasilus orientalis
 * Ergasilus rhinos Burris & G. C. Miller, 1972
 * Ergasilus sieboldi Von Nordmann, 1832
 * Ergasilus tenax L. S. Roberts, 1965
 * Ergasilus turgidus Fraser, 1920
 * Ergasilus versicolor C. B. Wilson, 1911
 * Ergasilus wareaglei S. K. Johnson, 1971
 * Ergasilus wilsoni