Influence of the tidal and rainfall cycles on the population structure and density of Mesacanthion hirsutum gerlach (nematoda, thoracostomopsidae) on a tropical sandy beach (Tamandaré Bay, Pernambuco, Brazil). Braz. j. oceanogr. 2011;59(3):253-258. doi:10.1590/S1679-87592011000300005