Distribution, abundance and adaptations of three species of Actiniidae (Cnidaria, Actiniaria) on an intertidal beach rock in Carneiros beach, Pernambuco, Brazil

Abstract

Bunodosoma cangicum Correa in Belém & Preslercravo, 1973; Actinia bermudensis (McMurrich, 1889) and Anthopleura krebsi Duchassaing & Michelotti, 1860 were studied in an intertidal beach rock at Carneiro’s beach, Pernambuco, Brazil. According to the environrnental factors five rnicrohabitats occupied by the species were identified. Random surveys were made and a framework was used to calculate the mean specific density of each species in the different habitats. Ten specirnens of each species were rneasured. The Mann-Whitney test was used to compare size and density of B. cangicum frorn different habitats. Specirnens of B. cangicum were found in three different habitats, with the lowest density (1.1 ind/m²) and the lowest size (1.2 x 3.8 cm, diam x height) in pools on the flats of the beach rock, exposed to the sun and to the rainfall. In this habitat, there was an increase in the ternperature and salinity of water during dry seasons and the species was almost absent during rainy seasons. In habitats 4 and 5, which were more protected, the mean density was 6.0 and 6.4 and the mean size of 4.5 x 6.3 cm and 5.3 x 6.4 cm, respectively. A. krebsi was present in two habitats with high density (24.5 ind/m²) in the habitat with longest air exposure time and this density seerns to be associated with asexual reproduction. A. bermudensis was present in only one habitat with low density (1.4 ind/rn²) and size of 2.0 x 2.2 cm. No differences were observed in the statistical cornparison of the density of B. cangicum in two protected zones (P > 0.05) which were thus used as one and cornpared with another unprotected zone. The resulfs showed significant differences (P <= 0.05). The comparison of size showed differences among the three zones (P <= 0.05).