Application of the isotopic mixing models in the ecology to trophic structure of the spider crab Libinia ferreirae (Decapoda: Majoidea)

Abstract

The FAPESP PhD proposal has the focus on the ecological interactions of marine fauna to understand the trophic chain with the use of stable isotopes tools as Isotopic Mixing Models. In this study, we intend to analyse the marine fauna inhabiting the area of the Iguape-Cananéia-Paranaguá Lagoon-Estuarine Complex, a "Biosphere Reserve of the Atlantic Forest and Natural Patrimony of Humanity" established by UNESCO. This range of habitats, from the top summits of the mountain to the vast stretches of desert shores, guarantees its great diversity. However, it is all of these ecosystems and landscapes which express the uniqueness of the region. In this way, the ecological interaction of marine species has been analysed, especially, the spider crab Libinia ferreirae that keeps interspecific ecological relationships with jellyfish and sea anemones. Up to date, 50 different organisms (invertebrates and vertebrate species) and 3 different classes of zooplankton are collected. These organisms were processed and analysed by means isotopic analyses ´13C and ´15N. A preliminary evaluation of these organism's interaction indicates five trophic levels. The aim of the current project is: analysing the data set thought the Stable Isotopic Mixing Models (SIMMs), and evaluating the data in the bioinformatics developed in packages of R as SIAR (Stable Isotope Analyses in R). These measuring instruments will clarify the relationship of the crab L. ferreirae when it is a medusa´s symbiont, when it is a host for many epibionts, and the crab's interaction within the trophic web. The internship opportunity will allow the establishment of an international partnership with the Prof. Stuart Bearhop (PhD) that will improve a scientific perspective and a network of the PhD student. Additionally, the PhD student (GRLG) will get an experience on a new technique that will be useful in her supervisor's laboratory, and she will be able to transfer this knowledge to lab staff in Brazil, that will open a new perspective of cooperation.