The ecology and physiology of inducible agonistic structures in two species of Anthozoa

The first two parts of this study document the presence of inducible agonistic structures in two different order of Anthozoa. Field and laboratory transplant experiments were performed with Discosoma sanctithomae (Corallimorpharia) and Erythropodium caribaeorum (Gorgonacea) to examine the nature of the induction of the structures and to determine their function in competitive interactions with adjacent species.; Discosoma sanctithomae used both modified marginal tentacles and mesenterial filaments to damage adjacent scleractinians. All colonies of Agaricia agaricites transplanted near D. sanctithomae were damaged. Initially D. sanctithomae adjacent to Meandrina meandrites were severely wounded. However, 67% recovered and retaliated within a one to six month period causing damage to M. meandrina which persisted for at least twelve months. Erythropodium caribaeorum develops fields of modified polyps along the edge of their colony adjacent to a variety of soft-bodied anthozoans. These polyps have elongate tentacles termed 'sweeper tentacles'. Such tentacles lack the side branches (pinnules) characteristic of octocorals in general, and bear a bulbous tip (acrosphere) densely packed with holothrich nematocysts. Transplant experiments showed that damage occurs to corals placed in contact with the gorgonian's sweeper tentacles and that sweeper tentacles could be induced when scleractinian corals contacted Erythropodium caribaeorum colony having exclusively normal tentacles.; Erythropodium caribaeorum is, so far, unique among soft-corals because of this ability to form specialized agonistic structures. The formation of the aggressive sweeper tentacles results in a reduction of symbiotic zooxanthellae which may lead to a reduced capacity for photosynthesis. The presence of the sweeper tentacles provide the opportunity to examine the relationship between costs of inducible defenses and the energetics resources of primary production. The second two parts of this study, measure primary productivity and respiration for both normal and sweeper tentacles in an attempt to detect energetic costs of maintaining sweepers. No significant differences were found between normal and sweeper tentacle P max, respiration rates, or P:R values for normal and sweeper tissue from the back-reef. However, both P max and the P:R ratio for normal tissue from the fore reef were significantly lower than normal tissue from the back-reef area. Alternative hypotheses to explain the differences in sweeper tentacle prevalence at two study sites are discussed in chapter 4. The presence of sweeper tentacles is dependent on an appropriate stimulus, a minimum colony size, and an energy supply to maintain them. (Abstract shortened by UMI.)...