Ecologia trÃfica das anÃmonas-do-mar Anthopleura cascaia e Anthopleura krebsi (cnidaria: anthozoa) em duas praias de Pernambuco, Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Studies of trophic ecology are fundamental to understanding the role that the species play in the ecosystem. Sea anemones are important components of reef environments, but few studies address the relationship anemone and its prey. So, it was developed a study on the species Anthopleura cascaia and Anthopleura krebsi on Piedade and Carneiros beach, in Pernambuco, to evaluate the diet, degree of food selectivity and niche overlap between species. Anemones were collected bimonthly from March 2007 to February 2008. The gastric contents found sorted, counted, measured and identified to the lowest level possible. From this analysis, we obtained values of absolute and relative abundance, richness, diversity and frequency of prey. Abundance and richness was compared with Log linear test. Spearman correlation Inex was used to verify the relation between (a) size of sea anemones species and (b) abundance of preys in the environment and in the gastric cavities. The GLM ANOVA test was applied to evaluate the selectivity by size. The mean size of anemones and of prey items were compared with a t-test. The niche overlap was estimated by the qualitative indices of similarity (Jaccard) and quantitative (Morisita). A. cascaia showed a larger size than A. krebsi, and a greater richness of prey items, 26 in Piedade and 16 in Carneiros beach. On Carneiros the main preys of A. cascaia were the bivalve Brachidontes solisianus and the barnacles Chthamalus bisinuatus. Piedade showed the same pattern, however, the barnacles were less abundant. It was found significant difference in diversity of prey found in the gastric cavities between the beaches and also between the dry and wet periods. A. krebsi used 12 items of prey on Carneiros beach and 10 in Piedade. B. solisianus was the most abundant and also the most frequent among preys of A. krebsi both in Piedade and Carneiros beach. The qualitative analysis of the niche overlap showed a low similarity between beaches and between species. However, in a quantitative analysis a high similarity between the situations was observed. A. krebsi had a smaller spectrum of prey, feeding predominantly on Brachidontes spp. at both beaches. Despite the partial overlap in food niche of the species with the same prey occupying a prominent place in the diet of A. cascaia and A. krebsi, it is possible that this does not represent a strong competition for food resources due to the high abundance of the majors preys. Both A. cascaia and A. krebsi would be polyphagous, with a predominance of mollusks and crustaceans in their diet. Despite of this study showed that sea anemones are selective, the low mobility and the use of juveniles of benthic species seem to indicate that studied species are passives and depending on wave and others invertebrateâs action to make their prey available.

ASSUNTO(S)

niche overlap sobreposiÃÃo de nicho nordeste do brasil diet northeast of brazil actiniaria dieta zoologia reefs recifes actiniaria

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