Prey selectivity of the octocoral Carijoa riisei at Pernambuco, Brazil

Abstract

This study was designed to evaluate prey selection (type and size) by the octocoral Carijoa riisei at Porto de Galinhas beach, Northeast Brazil, relating prey availability in plankton with the content inside polyps. Diatoms and cyanophytes were the predominant items found in both polyp gastric cavity and plankton. A correlation between prey abundance in the plankton and in the gastric cavity of C. riisei polyps was observed. Mastogloia sp. showed the highest positive electivity index (0.99). Benthonic items were found, with 0.51% of total consumed preys. The size amplitude of prey items in the plankton was similar to those found inside the polyps, although the mean prey size in the polyps (112.7 µm) was significantly lower than the value found in the plankton (240.5 µm). Thus, the study indicates some size selectivity in this species or at least size limitation. From the results, we concluded that the octocoral C. riisei is an opportunistic polyphagous species in the Brazilian northeast coast, showing suspensivorous passive filtering feeding habit with a preference for small prey items and evidencing its important ecological role in the reefal ecosystem as responsible for bidirectional energy transference between pelagic zones and the benthos.

Chemical and biological aspects of octocorals from the Brazilian coast

“…Almost all utilize symbiotic photosynthetic zooxanthella as a major energy source. However, most will readily eat, as passive suspensivorous feeders, any free-floating food, such as phytoplankton and zooplankton out of the water column (Lira et al, 2009;Gomes et al, 2012). They are integral members of the reef ecosystem and provide a habitat for fish, snails, algae and other marine species.…”

Trophic ecology of the zoanthidPalythoa caribaeorum(Cnidaria: Anthozoa) on tropical reefs

“…Most of the studies, however, were undertaken in temperate regions, while tropical coral reef ecosystems have distinct dynamics and high productivity even in oligotrophic waters (Lewis, 1977;Rougerie et al, 1992), with the reef fauna rapidly removing planktonic biomass (Erez, 1990). Studies investigating the diets of benthic cnidarians in these environments have demonstrated the great importance of phytoplanktonic prey (Coma et al, 1999;Lira et al, 2009, Gomes et al, 2012 with a pattern different from temperate species and similar to the diet of P. caribaeorum in northeastern Brazil. The diet of P. caribaeorum seems to be similar in the two beaches studied, without significant variations in their richness or abundance between the dry and rainy seasons.…”

“…Studies of reef environments have revealed the importance of corals and other suspensivorous organisms as energy transformation links between the pelagic and benthic domains (Lasker, 1976;Smetacek, 1984;Lira et al, 2009;Gomes et al, 2012). As they are commonly preyed upon by reef fish, these organisms pass the biomass fixed by plankton on to higher levels of the food chain (Cole et al, 2008;Rotjan & Lewis, 2008;Francini-Filho & Moura, 2010) and are fundamental to energy fluxes and marine trophic webs.…”