Irish Osmundea spp.: Food or shelter for Aplysia sp.?

Abstract

The Irish coastline is approximately 7500 Km long representing one of the most biodiverse and rich-species habitats in Europe. With only few studies conducted in the North East Atlantic region, Irish waters can be a great source of new and unexplored chemical diversity. Four different Osmundea sp., commonly found in intertidal zone, have been described from Irish waters. Aplysia sp., is a sea hare which has been found to be associated with Osmundea algae. This project is focusing on the isolation and characterisation of secondary metabolites from Osmundea spp. and Aplysia sp. samples collected from the shore of Western Ireland in county Galway. The ultimate aim is to compare the chemistry produced by these two marine organisms and determine whether the sea hares are sequestering the compounds from the algae or they are using the Osmundea spp. as a shelter from predators and strong water currents. Thus half the Aplysia sp. collected were allowed to fast prior to analysis affording an opportunity to sample the chemistry contained within the sea hares rather than that contained within the digestive tract. The algal and animal samples were extracted separately in organic solvents followed by purification and isolation of secondary metabolites by means of Medium Pressure Liquid Chromatography (MPLC) and High Performance Liquid Chromatography (HPLC). Comparisons between the algal and sea hare extracts were carried out through metabolomics analysis using Liquid Chromatography-Mass Spectrometry (LC-MS) and Gas Chromatography-Mass Spectroscopy (GC-MS). Moreover, the structures of pure metabolites were elucidated by means of 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy.