Ecologia alimentar de Zoanthus sociatus e Protopalythoa variabilis (Cnidaria: Zoantharia) no litotal de Pernambuco, Brasil

Abstract

This study investigated the feeding ecology of zoanthids Zoanthus sociatus and Protopalythoa variabilis. Colonies of this species were sampled in the infralittoral zone of reefs in northeastern Brazil (may/2013 to february/2014). Polyps (n = 400) were examined the gastric cavity and prey found were counted, measured and identified. We calculated the richness and total abundance of prey items. The GLM test two-way ANOVA was used to compare the abundance and ricness between period and species. The biovolume of preys were calculated to characterize the most important food items in terms of their biomasses. To evaluate the selectivity, zoanthid and plankton samples were collected in the dry season and rainy. The results revealed the occurrence of seven taxa of phytoplankton and zooplankton three, and particulate organic matter. Pennales diatoms were the most abundant and most frequent prey and, together with invertebrate eggs, constituted the most important food items in terms of their biomasses. There were significant differences in abundance and richness among the species and between periods, with a significant interaction between these factors, only for abundance. The mean size of prey items within the polyps of Z. sociatus (26.35 ± 59.10 μm) and polyps of P. variabilis (26.56 ± 54.71 μm) was significantly smaller than in the plankton (54,14 ± 107,25 μm). As for the type prey, Zoanthus sociatus and Protopalythoa variabilis feed predominantly diatoms. The results, the two species are suspensívoras, feeding mainly on small phytoplankton. These results corroborate those previously found for the zoanthid P. caribaeorum in the same place, showing that this group has an important role in energy flow in reefs, transferring biomass of plankton to superiroes groups of the chain. This is fundamental to the Brazilian reefs where coverage of other suspensívoros as coral, is very low.