In order to know the composition of free living
marine nematodes, samples were collected in three sites at
Isla Mujeres and four sites at Banco Chinchorro, Quintana
Roo, Mexico. At Isla Mujeres, 34 genera were identified
corresponding to 17 families and three orders. Chromadorida
was the order best represented with 20 genera, followed by
the order Monhysterida with eight genera and the order
Enoplida with six genera. Family Desmodoridae had the
highest number of genera (five). The most abundant genera
(individuals 0.001m-2) were: Terchellingia longicaudata (34),
Spirinia parasitifera (23), Croconema cincta (22),
Eubostrichus porosum (20), and Xyala riemmani (18). Station
E2 had the high nematode abundance (125 individuals
0.001m-2), whereas station E3 had the lowest amount (85
individuals 0.001m-2). At Banco Chinchorro, nematofauna
corresponded to three orders, 17 families, and 49 genera.
Chromadorida had the highest number of families and genera
(9 and 34 respectively). Enoplida had five families and eight
genera, whereas Monhysterida had three families and seven
genera. Desmodoridae showed the highest number of genera
(11). Croconema cincta, presented the highest abundance (36
individuals 0.001m-2) followed in descendent order by
Dorylaimopsis sp. 1 (24), Croconema otti (22), Paracomesoma
longispiculum and Trypilodes marinus with 20, respectively.
CN had the highest abundance by station (243 individuals
0.001m-2), whereas CL had the lowest (37 individuals
0.001m-2). In both localities, dominant nematodes had small
and annulated bodies with many somatic setae, typical of
sandy environments. All species are new records for Mexico.