Diversity and Distribution of Cyatholaimidae (Chromadorida: Nematoda): A Taxonomic and Systematic Review of the World Records

Nematoda is a very species-rich phylum that has successfully adapted to almost all types of ecosystems. Despite their abundance and ecological importance, the taxonomic knowledge nematodes still limited identification species not trivial. In Cyatholaimidae, relatively common abundant family free-living nematodes, organisms challenging due overlap some generic diagnoses absence updated systematic reviews. Here we systematically reviewed about diversity, providing list valid species, diagnostic characters genus level, geographical habitat distribution species. The review systematized total 619 records. occurrences were classified into biogeographic ecoregions habitats. Cyatholaimidae includes 211 in 20 genera. genera can be differentiated based on six diagnostics characters, namely: pattern cuticle ornamentation; number longitudinal rows pore-complex cuticle; structures buccal cavity; presence/absence pharyngeal bulb; pre-cloacal supplements aspect; shape gubernaculum. mainly marine mostly occurring Coastal Zone. Four three registered freshwater terrestrial habitats, respectively, Paracyatholaimus . About 38% occur more than one type habitat, under different environmental conditions, suggesting broad niche. occurrence congeneric habitats indicates that, throughout evolutionary history family, multiple shift events have occurred. occurs worldwide 74 ecoregions, majority records are North Sea Western Mediterranean. Most endemic ecoregion, examples broadly distributed ones may result misidentifications or cases long-distance dispersal, especially for those associated with biological substrates.