Ergasilus is a genus of copepod

Copepod

Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...

 crustaceans occurring in both the ocean and fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

, often called gill lice. The females are parasitic upon the gills of fishes. This is similar to members of the crustacean order Arguloida (fish lice). Being copepods, gill lice have a single median eye on their head. The second antenna

Antenna (biology)

Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

e are modified into prehensile pincers. Male gill lice are free-living.

Species include:

• Ergasilus anchoratus Markevich, 1946
• Ergasilus arthrosis L. S. Roberts, 1969
• Ergasilus auritus Markevich, 1940
• Ergasilus briani Markevich, 1932
• 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