Gill Monogenea of deepwater and surface fish in southeastern Australia

The faunas of gill Monogenea of marine teleost fishes in deep and surface waters of southeastern Australia are compared, based on extensive surveys: 1563 fish (66 or 67 species, 35 families, 15 orders) in deepwater; 1862 fish (46 species, 26 families, 7 orders) in surface water. Relative species diversity (number of species of Monogenea/all fish species examined) is approximately five times greater in surface waters. There is a similarly low relative species diversity of Monogenea in the northwestern Pacific and northwestern Atlantic deepwater. Deepwater Monogenea in all seas belong mainly to the Diclidophoroidea (13 of 19 species in southeastern Australia, 14 of 17 species in the northwestern Pacific, at least 9 of 12 (?) species in the northwestern Atlantic) predominantly Diclidophoridae. Important groups of surface Monogenea in southeastern Australia are the Microcotylidae (34 of 83 species), Dactylogyridae Ancyrocephalinae (15 species) and Capsaloidea (12 species); only 10 species belong to the Diclidophoroidea and 2 of those to the Diclidophoridae. It is concluded that deepsea Monogenea in southeastern Australia show no or very little relationship with surface Monogenea of the same geographical area, but close relationship with Monogenea in the deepsea of other geographical areas. Some deepsea Monogenea have a wide geographical distribution in the Atlantic and Pacific Oceans. Arctic and Antarctic Monogenea also are not related to deepwater forms. The main group of deepsea Monogenea is considered to be archaic.