Efeito das relações competitivas interespecíficas envolvendo Tubastraea spp. (Scleractinia, Dendrophyllidae) e Palythoa caribaeorum (Zoantharia, Sphenopidae)

Abstract

The space is a limited resource for the establishment of benthic species on consolidated substrates. Considering the introduction of invasive species, the effects of the interspecific competitive interaction must be evaluated, once the prevalence of these organisms over native species depends upon a repertory of strategies not fully understanding. Tubastraea corals became overspread along the Atlantic Ocean, being majorly observed on artificial substrates. In contrast with the Great Barrier Reef in the Pacific Ocean, where more than 300 species have been identified, the diversity of shallow water scleractinians in Brazil is reduced (21 species) with major reef building species represented by the genus Mussimilia. Palythoa caribaeorum is a native zoanthid with high growth rates, and colonies with short polyps embbebed in the coenenchyma. The species forms thick mats on hard substrates, also producing a strong biotoxin: the palytoxin. To study the interaction between Tubastraea spp. and P. caribaeorum, a manipulative experiment was developed in situ in the Todos-os-Santos Bay (12ºS, Bahia State). Two species (and respective morphtypes), Tubastraea tagusensis (dendroid) and Tubastraea coccinea (plocoid), were tested. No tissue damage was detected in any Tubastraea sample during the interspecific experiment. P. caribaeorum underwent retraction, mucus deposition and overgrowth, being a reduction of the area occupied by the zoanthid identified only during the interaction with T. tagusensis. Beyond a chemical warfare between two strong alleopathic organisms, the prevalence of the dendroid morphtype over Palythoa caribaeorum brings into concern that the zoanthid response may be also influenced by Tubastraea morphology.