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Echinolittorina peruviana is the most common gastropod in the high intertidal zone of Peru, representing more than 80% of the individuals present at that zone. Experimental removal of snails was used to evaluate their effects on (a) abundance of epilithic biofilm, (b) barnacle recruitment, and (c) abundance of macroalgae under 'normal' conditions of the El Niño Southern Oscillation (ENSO). Experiments were carried out from October 2005 to April 2007 at two intertidal levels of a semi-protected rocky shore of central Peru. Results demonstrated that E. peruviana is able to control biofilm abundance and barnacle recruitment at both heights investigated, with marked effects in the lower zone. Erect macroalgae ( Ulva spp. and Gelidium spp.) were less affected by grazing; but negative effects were observed on macroalgal crusts. Season and physical stress seem to play a more important role in the abundance of macroalgae in the high intertidal. Our results are similar to those reported elsewhere for high shore littorinids and represent baseline data to understand how the role of intertidal consumers will vary under the cold (La Niña) and warm (El Niño) phases of ENSO on these shores. [ABSTRACT FROM AUTHOR]

The reproductive cycle of the entocommensal nemertean Malacobdella arrokeana inhabiting Panopea abbreviata from San José Gulf, Patagonia, Argentina, and the nemertean–host relationship were investigated. The mature nemertean population showed a sex ratio of 1:0.64, with females predominating. The number of individuals of M. arrokeana per host varied from 1–60 individuals (mean±SD=3.7±9.4 mm). Different stages of gonadic development were observed in individual nemerteans. Spawning peaks occurred during late summer and early spring. Sexually mature individuals of both sexes were present year round, possibly indicative of a continuous breeding period. Our results suggest that M. arrokeana has no cannibalistic habits and confirm its entocommensal symbiosis with P. abbreviata. [ABSTRACT FROM AUTHOR]