Abundancia y distribución de Pontodrilus litoralis en las costas cercanas al Faro de Cabo Rojo, Puerto Rico
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The purpose of this investigation was to determine the structure and dynamics of the populations of the oligochate Pontodrilus litoralis on the coasts near the Cabo Rojo Lighthouse in Puerto Rico. During the months of May of 2008 and February 2009, sampling was made at low tide on the sandy littoral shores of two beaches on each side of the lighthouse. Distances from the tide mark in sand was taken into account. Environmental factors such as temperature, pH, soil moisture, organic matter, and surface accumulation of plant debris were registered. Spatial distribution of Pontodrilus litoralis was determined to be aggregate in clusters. These clusters were predominant right at the high tide marking where sand was always humid but never completely submerged under seawater. Organic matter and temperature were determined to be the primary factors in the distribution of the oligochate. Sites with the lowest temperatures recorded seemed to have the most number of individuals. Sites with the most accumulation of surface plant debris recorded the lowest temperatures as well as the highest organic matter contents. Sites with clusters of individuals recorded the most acidic pH due to heightened cell respiration rates where individuals are numerous. Only a small percentage of the individuals sampled had reached adulthood, this indicates a high reproductive output once the juveniles enter the reproductive stage of adulthood but a relatively slow growth to reach it.