Diversity of nematoda in a Caribbean Atoll: Banco Chinchorro, Mexico

Free-living marine nematode assemblages were studied at four sites in Banco Chinchorro, Caribbean Sea, Mexico: Cayo Norte, Cayo Lobos, Isla Che, and Cayo Centro. Three orders, 21 families, 65 genera, and 98 species represented the nematode fauna. The order Chromadorida was the best represented with nine families, and 56 species, followed by Enoplida (nine families, 22 species), and Monhysterida (three families, 16 species). Desmodoridae had the highest number of species (3 1). The highest nematode density (1.83 x 10(5) nematodes m(-3)) was found at Cayo Centro, followed by Cayo Norte (1.77 x 10(5) nematodes m(-3)). Lowest nematode density was found at Isla Che (3.18 x 10(4) nematodes m(-3)). Cayo Norte had also the highest number of species (47), with a diversity of H'= 5.03 bits ind(-1) and an evenness value of 0.91; Cayo Lobos and Cayo Centro had a similar number of species (41 and 40, respectively) and a similar diversity (H'= 4.76 bits ind(-1) and H'= 4.67 bits ind(-1)). Isla Che presented the lowest number of species (14) and diversity (H'= 3.55 bits ind(-1)). At Cayo Lobos, an inner station, nematodes had small and annulated bodies with many somatic setae, typical of sandy environments with high energy. At the family level, the nematode fauna at Banco Chinchorro is similar to other assemblages found in the Caribbean. All species registered in this study add new evidence of their geographic range in the western Caribbean. The nematode fauna surveyed represent possibly up to 69% of new species. Nematoda diversity values found at Banco Chinchorro were higher than those known in similar environments.