DNA metabarcoding unveils niche overlapping and competition among Caribbean sea urchins

Detailed information of trophic interactions among consumer-resources in food webs is usually limited due to the lack of accurate identification of eaten food resources. The use of DNA-metabarcoding has been proven useful for molecular identification of the numerous taxa present in stomach contents. Here, we characterize the diet and trophic behavior of four sea urchin species inhabiting shallow waters of Puerto Rico using this molecular technique. We extracted, sequenced, and analyzed DNA from the gut content of a total of 60 individuals collected at three sites at the northeastern coast of Puerto Rico. Our results demonstrated that seaweeds were the dominant food source for the four sea urchin species at all three sites, but also small protists, fungi and metazoans were important components of sea urchin's diet. Interspecific differences in diet were also found among sites. PERMANOVA analysis detected significant differences among species (Pseudo-F 1.755, p < 0.001), and among sites (Pseudo-F 2.52, p < 0.001). A SIMPER analysis showed that in all cases the main taxa causing differences between species and sites were macroalgae (Rhodophyta, Chlorophyta and Ochrophyta) with some contribution of small eukaryotes (Apicomplexa and Bacillariophyta). This diet characterization in sea urchins revealed a generalist omnivore behavior, but with a clear dominance of algae as a main dietary component. Thus, we found a potential inter-specific competition due to niche overlapping, which seems to be more common than initially thought

Assessing the reliability of two tagging techniques in the echinoid Echinometra lucunter

4 páginas, 2 figurtas, 1 tabla.Several tagging methods have been tested to assess important aspects on ecology, such as population dynamic, movement pattern, and behavioral studies. The use of external and internal tags has been extensively used for individual identification in sea urchins. Different types of tags have been used in Echinometra lucunter, considered the most common sea urchin in the Caribbean. We evaluated whether PIT-tags and S-tags may affect retention, survival and growth rates under laboratory conditions, using the sea urchin E. lucunter as a model. The type of tag was critical in terms of retention rates, with significant differences between PIT-tag and S-tags groups (Kruskal–Wallis, H = 5.33, p = 0.021), and mortality exhibited similar rates among treatments. No significant association was detected between initial maximum test diameter and the number of weeks the individuals retained neither the PIT-tag (r = −0.09, p = 0.620), nor the S-tag (r = −0.175, p = 0.413), and no significant differences in growth rate were detected among treatments (F = 1.66, df = 2, p = 0.401). We do not recommend the use of S-tag due to low retention; but we support the use of PIT-tags in E. lucunter for their positive performance displayed in terms of retention and survival but with caution, particularly in those studies requiring 80% or higher retention.Peer reviewe

The Epibiotic Microbiota of Wild Caribbean Sea Urchin Spines Is Species Specific

Caribbean sea urchins are marine invertebrates that have experienced a decline over the years. Studies on sea urchins have focused primarily on the microbiome of the coelomic fluid or the gut microbiota. In this study, the epibiota community associated with four wild Caribbean sea urchin species, Lytechinus variegatus, Echinometra lucunter, Tripneustes ventricosus, and Diadema antillarum, was characterized for the first time. Using 57 sea urchin animal samples, we evaluated the influence of animal species, trophic niches, and geographical location on the composition of the epibiotic microbiota. We found significant differences in the bacterial biota among species and trophic niches, but not among geographical locations. L. variegatus exhibited the highest alpha diversity with high dominance of Fusobacteria, Planctomycetes, and Cyanobacteria, whereas T. ventricosus and D. antillarum were dominated by Firmicutes. T. ventricosus inhabiting the seagrass biotope dominated by Thalassia testudinum meadows had mostly Endozoicomonas. In contrast, samples located in the reef (dominated by corals and other reef builders) had a higher abundance of Kistimonas and Photobacterium. Our findings confirm that the epibiotic microbiota is species-specific, but also niche-dependent, revealing the trophic networks emerging from the organic matter being recycled in the seagrass and reef niches. As echinoids are important grazers of benthic communities, their microbiota will likely influence ecosystem processes

DNA metabarcoding unveils niche overlapping and competition among Caribbean sea urchins

Detailed information of trophic interactions among consumer–resources in food webs is usually limited due to the lack of accurate identification of eaten food resources. The use of DNA-metabarcoding has been proven useful for molecular identification of the numerous taxa present in stomach contents. Here, we characterize the diet and trophic behavior of four sea urchin species inhabiting shallow waters of Puerto Rico using this molecular technique. We extracted, sequenced, and analyzed DNA from the gut content of a total of 60 individuals collected at three sites at the northeastern coast of Puerto Rico. Our results demonstrated that seaweeds were the dominant food source for the four sea urchin species at all three sites, but also small protists, fungi and metazoans were important components of sea urchin’s diet. Interspecific differences in diet were also found among sites. PERMANOVA analysis detected significant differences among species (Pseudo-F 1.755, p < 0.001), and among sites (Pseudo-F 2.52, p < 0.001). A SIMPER analysis showed that in all cases the main taxa causing differences between species and sites were macroalgae (Rhodophyta, Chlorophyta and Ochrophyta) with some contribution of small eukaryotes (Apicomplexa and Bacillariophyta). This diet characterization in sea urchins revealed a generalist omnivore behavior, but with a clear dominance of algae as a main dietary component. Thus, we found a potential inter-specific competition due to niche overlapping, which seems to be more common than initially thought