Distribution of brachyuran larvae in an Amazonian estuary as evidence for retention and export

Abstract

Abstract Brachyuran crabs, like other decapod crustaceans, adopt a number of different strategies for larval dispersal. We verified the influence of variations in temperature, salinity, and pH on the abundance and taxonomic composition of brachyuran larvae in an Amazonian estuary and found evidence of both retention and export dispersal strategies. We identified larvae of 20 different taxa belonging to the families Grapsidae, Ocypodidae, Panopeidae, Pinnotheridae, and Sesarmidae. Ucides cordatus (Linnaeus, 1763) (Ocypodidae), Pachygrapsus gracilis (Saussure, 1857) (Grapsidae), Leptuca cumulanta (Crane, 1943) (Ocypodidae), and Armases rubripes (Rathbun, 1897) (Sesarmidae) were the most abundant species. Most of the taxa present in the study area were at the zoea I stage but later larval stages were found in some species, indicating retention and export. Results were supported by canonical correspondence analysis and general linear model, which related larval community structure and reproduction patterns to variations in salinity, influenced primarily by the enormous discharge of the Amazon River and the high rainfall levels in the region. Further investigations of the distribution of larvae on the continental shelf are necessary to confirm the identified dispersal patterns. The study also presents novel data on the composition, abundance, and dispersal of brachyuran larvae in the tropical estuaries of the Amazon River.