Resumen

RIVADENEIRA, MARCELO M.  y  OLIVA, EDUARDO. Patterns of local movement behavior in Phymactis clematis Drayton (Anthozoa: Actiniidae). Rev. chil. hist. nat. [online]. 2001, vol.74, n.4, pp. 855-863. ISSN 0716-078X.  doi: 10.4067/S0716-078X2001000400012.

Phymactis clematis Drayton is the most abundant and one of the largest species of sea anemone along the South American coast. Likewise other sea anemone species, the adults of the P. clematis would have an active ability to make local movements. However, these have not been properly described, and causal factors are unknown. In this work we try to describe some of the basic patterns associated to the local movement behavior in P. clematis, assessed indirectly from the presence of bare rock halos around individuals in two rocky intertidal sites in the coast of northern Chile (Cavancha and Colorado Chico). Movements were more frequent and had a higher intensity at Colorado Chico, where over 50 % of individuals showed movements, although they were mainly lower than 60 mm in length. At Colorado Chico, movements would occur in individuals larger than 40 mm of pedal diameter, whereas their intensity would decrease with body size. We discussed that causes of higher movement activity at Colorado Chico could be associated to the higher abundance and lower inter-individual spacing, which would produce physical interference among individuals. In this way, we suggested that the patterns associated to the individual's body size would arise secondarily, being dependent on the levels of local abundance. Despite local movements of P. clematis at Colorado Chico occurred at a scale of a few centimeters, they could be affecting significantly the inter-individual spacing, increasing the average nearest neighbor distance. We argue that local movements could be an effective mechanism reducing the intraspecific competition in P. clematis

Palabras clave : Phymactis clematis; sea anemones; local movements; nearest neighbor distance; rocky intertidal.