Evaluation of Purple sea urchins Paracentrotus lividus grazing on alien species Rugulopteryx okamurae.

Abstract

Abstract Rugulopteryx okamurae is an invasive nonindigenous marine species (NIS) of macroalgae present in the benthic communities of the Strait of Gibraltar that have colonised quickly most of the coast of this strait triggering ecological, economic and social consequences. Sea urchins (Paracentrotus lividus) are generalist herbivore with potential to provide resistance to this NIS. The objectives of this study were to assess if the generalist herbivore sea urchin consumes the invasive macroalgae R. okamurae under laboratory conditions, to known the grazing preferences when this NIS macroalgae is offered together with the native species Ulva ohnoi, as well as to find biochemical tissue markers related with R. okamurae ingestion. In this study two experiments were carried out. In the first experiment sea urchins were evaluated in groups for two months, and afterwards, in a second experiment, the same specimens were used to analyse individual preferences, feeding rates and fatty acid profiles. Daily food consumption rates showed that sea urchins accepted the NIS seaweed R. okamurae as food under laboratory conditions and even increase its intake over a long exposure period. In the same way, we observed that elective values for non-native species improve when P. lividus was exposed to R. okamurae for a long time, also showing differences among individuals. Regarding the fatty acids profiles of tissues, our results shown that arachidonic acid discriminates intestines of sea urchins fed with R. okamurae, while the gonad fatty acid composition was not directly related with diet.