Effect of sedimentation on the attachment and detachment capacity of the sea anemone Anemonia alicemartinae (Cnidaria: Anthozoa) on hard substrates

摘要

Anemonia alicemartinae is a cryptogenic species on the Chilean coast, where it is an invader (i.e., increases its distribution over time). Attaches to hard substrates in intertidal and subtidal systems from the northern Chilean coast to the Concepcion Bay. Apparently, their reproduction is mainly asexual, without a larval phase, so it has been proposed that their dispersion occurs through a mechanism of detachment and re-attachment to the substrate, which can be stimulated by biotic and abiotic conditions. In this work, was evaluated the effect of sand on said dispersion mechanism, for which sediment collectors were installed at 14 sampling points, in the coast of Lirquen, in the southeastern of Concepcion Bay (the southern limit of distribution of this species in the SE Pacific). The results indicated that the density of anemones decreases exponentially with the amount of sediment, which corresponded mainly to fine and medium sands (i.e., between 0.125 and 0.5 mm in diameter). Laboratory experiments indicate that anemones attached to substrates with more sands take less time to detach, while those attached to substrates without sands take three times as long to do so. The results suggest that the anemones could perceive the presence of sand as unfavorable conditions, stimulating the detachment of the individuals, in search of more favorable habitats. The role of sand in long-distance dispersal of the species is also discussed.