The family Oithonidae Sars, 1913 includes primarly coastal marine planktonic species, with some others found in brackish water habitats, only a few (genus Oithona) occurring in strictly freshwater environments. Only two genera are known for italy, viz. Oithona Baird, 1849 and Paroithona Farran, 1908

Genus Oithona Baird, 1849

Oithona atlantica Farran, 1908 3, 5
Oithona brevicornis Giesbrecht, 1891 3, 5
Oithona decipiens Farran, 1913 3, 5
Oithona hebes Giesbrecht, 1891 3
Oithona linearis Giesbrecht, 1891 3, 5
Oithona longispina Nishida, 1977 3, 5
Oithona nana Giesbrecht, 1892 3, 4, 5
Oithona plumifera Baird, 1843 3, 4, 5
Oithona setigera (Dana, 1849) 3, 4, 5
Oithona similis Claus, 1866 3, 4, 5 *
Oithona tenuis Rosendorn, 1917 5
Oithona vivida Farran, 1913 5

* syn. Oithona helgolandica Claus, 1863

Genus Paroithona Farran, 1908

Paroithona parvula Farran, 1908 5

Family Cyclopinidae Cobbold, 1879 (NEW ENTRY)

Genus Cyclopina Claus, 1863

Cyclopina hadzii Petkovski, 1955 3 (NEW ENTRY)
Cyclopina ensifera Grandori, 1925 4 (NEW ENTRY)

Family Smirnovipinidae Martinez Arbizu (in press) (NEW ENTRY)

Genus Cyclopinoides Lindberg, 1953

Cyclopinoides bisetosa (Grandori, 1925) 4 (NEW ENTRY)

Family Schminkepinellidae Martinez Arbizu (in press) (NEW ENTRY)

Genus Muceddina

Muceddina multispinosa Jaume & Boxshall 1996 Sa (NEW ENTRY)

Family Lernaeidae Cobbold, 1879

Genus Lernaea Linnaeus, 1758

Lernaea cyprinacea Linnaeus, 1758 N

Family Ascidicolidae Thorell, 1859 Cobbold, 1879

Genus Ascidicola Thorell, 1859

Ascidicola rosea Thorell, 1859 [distribution not specified]

Genus Enterocola van Beneden, 1869

Enterocola clavelinae Chatton & Harant, 1929 [distribution not specified]
Enterocola fulgens van Beneden, 1860 [distribution not specified]
Enterocola pterophora Chatton & Harant, 1929 [distribution not specified]

Genus Mychophilus Hesse, 1965

Mychophilus roseus Hesse, 1865 [distribution not specified]

Genus Enteropsis Aurivillius, 1885

Enteropsis chattoni Monniot, 1961 [distribution not specified]
Enteropsis roscoffensis Chatton & Brement, 1909 [distribution not specified]

Genus Haplostoma (Cau, 1886)

Haplostoma banyulensis Brement, 1909 [distribution not specified]
Haplostoma mizoulei Monniot, 1962 [distribution not specified]

Genus Enterognathus Giesbrecht, 1900

Enterognathus comatulae Giesbrecht, 1900 3