Assessing grazing of Rugulopteryx okamurae (Ochrophyta) by the sea urchin Paracentrotus lividus (Echinodermata): a prospect for the biocontrol of the alien species?

ABSTRACT

Rugulopteryx okamurae is an invasive non-indigenous species (NIS) of marine alga present in the benthic communities of the Strait of Gibraltar, where it has colonized most of the coast triggering ecological, economic and social consequences. The purple sea urchin Paracentrotus lividus is a generalist herbivore with potential to provide resistance to this NIS. Two experiments were carried out to determine if (i) P. lividus consumes R. okamurae under laboratory conditions, (ii) to assess its grazing preferences when this NIS is offered together with the native Ulva sp. and (iii) to find biochemical tissue markers related to R. okamurae ingestion. In the first experiment, sea urchins fed with R. okamurae, Ulva sp. or both diets were evaluated in groups for two months. Ingestion, food preference, growth and survival were assessed. In the second one, the same specimens from the R. okamurae and mixed diets were used to analyse their individual preferences, ingestion rates, growth and fatty acid profiles during another two months. Ingestion rates showed that sea urchins accepted the NIS R. okamurae as food under laboratory conditions, increasing its intake after a long exposure period. The electivity values for R. okamurae also increased when P. lividus was exposed to this alga for a long time. Regarding the fatty acids profile of tissues, the results showed that intestinal arachidonic acid (ARA, 20:4n-6) clearly differentiates sea urchins fed with R. okamurae from those fed with the mixed diet. ARA also appeared to be related to the feeding preferences, highlighting this fatty acid as a reliable marker of R. okamurae ingestion. Further research is needed in order to determine P. lividus feeding behaviour and its role as a biocontrol species in the areas invaded by R. okamurae.

Highlights

• Sea urchin Paracentrotus lividus can feed on the alien macroalga Rugulopteryx okamurae.

• Ingestion rates and electivity increase after long exposure periods.

• Intestinal arachidonic fatty acid can be used as dietary biomarker.

KEYWORDS:

• Biocontrol
• dietary biomarkers
• fatty acids
• macroalgae
• non-indigenous species

Acknowledgements

We would like to express our gratitude to the public agencies of Junta de Andalucía AMAYA and AGAPA for their assistance in providing seaweeds and sea urchins. We also thank the Strait of Gibraltar Natural Park for issuing the necessary permits for harvesting the seaweed. Finally, we would like to thank Marcus Dellibovi for his assistance in correcting the English of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2024.2352840

Supplementary fig. S1. Macroalgal biomass loss (% WW) in the different treatments and controls during the experiments 1 and 2.

Supplementary fig. S2. Correlations between the average ingestion rates of R. okamurae and Ulva sp. for sea urchins fed with both algae (RO+U).

Supplementary fig. S3. Correlation between Ivlev’s electively index and the level of intestinal ARA for sea urchins fed with both algae (RO+U) during the experiment 2.

Author contributions

I. Hachero-Cruzado, M. Castilla-Gavilán, M. Muñoz-Martínez, E. Zuasti and T. Jiménez: experiments conception and design, material preparation, data collection and analysis. I. Hachero-Cruzado: writing of the first draft of the manuscript. M. Castilla-Gavilán: reviewing and editing manuscript. All authors read and approved the final manuscript.

Data sharing

The datasets generated during and/or analyzed during the current study will be available by the corresponding author under reasonable request.

Additional information

Funding

This work was supported by the European Maritime and Fisheries Fund project ‘Estudio de caracterización del alga invasora Rugulopteryx okamurae y posible valorización de su biomasa en las costas de Andalucía’ [FEM.DIP2019.001]. Marta Castilla-Gavilán was supported by a ‘Margarita Salas’ post-doctoral grant from the Spanish Ministry of Universities funded by the European Union – NextGeneration EU program.