Nematods, with more than 100.000 described species, are widely distributed over the World, both in surface (fresh, brackish and sea waters) and in groundwater habitats, as well as they represent the most common and plentiful group in the interstitial and meiofaunal bioceoenoses.

As regard the subterranean nematods, it must be remarked that often it could be difficult to distinguish between true stygobitic and occasional, stygophilic species, as they do not have particular morphological specializations to groundwater life, the only adaptation to the stygobiont way of life being their elongated and slender body shape. Notwithstanding, several species regualarly live in the subterranean realm, where they constitute the most prolific group, both as regard the individual and species richness.

Despite their remarkable abundance and distribution, the nematods are poorly represented in ground waters of Italy. Only eight taxa are actually known from this country and, moreover, they are confined only to the east part of the Alpine province.

Genus Theristus

Theristus athesinus Andrassy 1962 (1) *
Theristus ruffoi Andrassy 1959 (1) *
Theristus vesentinae Andrassy 1962 (1) *

Genus Panagrolaimus

Panagrolaimus ruffoi Andrassy 1962 (1) *

Genus Onchulus

Onchulus nolli Goffark 1950 (1)

Genus Stenonchulus

Stenonchulus troglodytes Schneider 1940 (1)

Genus Mononchulus

Mononchulus italicus Andrassy 1959 (1) *

Genus Mylonchulus

Mylonchulus cavensis (Schneider 1940) (1)

A selected World bibliography on subterranean nematods can be found in: R.Eder (1984). Nematoda from continental subterranean aquatic habitats. Stygofauna Mundi: 124-12; R.Eder (1994). Nematods. Encyclopaedia Biospeologica. Societ� de Biosp�ologie, Moulis, Bucarest: 49-52. See also the Bibliography of the Italian Groundwater Fauna

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