The polychaete cryptofauna from Cozumel Island, Mexican Caribbean

The polychaete cryptofauna collected in dead coral substrates in the shelf of Cozumel Island, Mexican Caribbean is analyzed here. Samples were taken with SCUBA diving on transects perpendicular to the coastline (depths 2 to 22 m). Nineteen families, 36 genera and 42 species were found. The Eunicidae dominate in density and species richness with a mean density of 315 ind m⁻² (seven species), followed by the Syllidae with 94 ind m⁻² (five species) and the Amphinomidae with 73 ind m⁻² (three species). Eunice cariboea, a characteristic species of coral reef areas in the Gulf of Mexico (representing here 36% of the total collected, and Syllis (Typosyllis) ortizi are the dominant species in Cozumel. There is some effect related to depth and anthropogenic influence, on the density and species richness because the lowest values were found in the shallower sampling zones (approximately 332 ind m⁻² and 20 species, versus 931 ind m⁻² and 32 species, in the deeper zones) and the populations' composition at each site is quite different. Compared with other areas sampled in the extensive Mexican coral reef environments in the Gulf of Mexico, in Cozumel the densities of polychaetes and species richness are high.