Abundance and distribution of Pontodrilus litoralis in the shores of the Cabo Rojo Lighthouse, Puerto Rico

Abstract

The structure and dynamics of the populations of the oligochaete Pontodrilus litoralis on the coasts near the Cabo Rojo Lighthouse in Puerto Rico were studied. Sampling was made at low tide on the sandy littoral shores of two beaches (protected and exposed) on each side of the lighthouse. Environmental factors such as substrate temperature, pH, soil moisture and organic matter content, and anoxic sand and surface accumulation of plant debris were registered. Spatial distribution of P. litoralis was determined to be aggregate in clusters which were predominant right at the high tide marking where sand was always humid but never completely submerged under seawater. Organic matter and temperature were the primary factors in the distribution of the oligochaete. Sites with the lowest temperatures recorded seemed to have the most number of individuals. Those with the most accumulation of surface plant debris recorded the lowest temperatures as well as the highest organic matter contents. There were no significant differences in earthworm density between beaches or collection time. New collection sites for the species in Puerto Rico are also included.

Key words:

• Neotropical
• Caribbean
• Annelida
• Megascolecidae
• Acanthodrilidae