INTERSPECIFIC AGGRESSIVE BEHAVIOR OF THE CORALLIMORPHARIAN CORYNACTIS CALIFORNICA (CNIDARIA: ANTHOZOA): EFFECTS ON SYMPATRIC CORALS AND SEA ANEMONES.

Abstract

Corallimorpharians are sessile cnidarians that are morphologically similar to the actiniarian sea anemones and scleractinian corals. This study describes for the first time the behavioral mechanism and effects of aggression by a corallimorpharian. Polyps of the temperate clonal corallimorpharian Corynactis californica extruded their mesenteries and associated filaments onto members of certain species of sea anemones and corals. They did not exhibit this behavior intraspecifically, and members of different clones of C. californica remained expanded upon contact. In contrast, members of four species of corals and zoanthids responded to contact with C. californica by contracting their tentacles, and members of three sea anemone species bent or moved away, detached from the substrate, or attacked using their aggressive structures. When interspecific contact was prolonged, individuals of C. californica extruded filaments onto, and killed polyps of, the sea anemones Anthopleura elegantissima and Metridium senile within 3 weeks, and the corals Astrangia lajollaensis and Balanophyllia elegans within 4-10 months under laboratory conditions. The use of extruded mesenterial filaments by C. californica to attack members of other anthozoan species is similar to the aggressive behavior exhibited by many scleractinian reef corals. Field observations suggest that C. californica may use this agonistic behavior during interspecific competition for space on hard marine substrate.