Solid phase extraction and metabolic profiling of exudates from living copepods

PeerJ. 2016 Jan 12:4:e1529. doi: 10.7717/peerj.1529. eCollection 2016.

Abstract

Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding or induce defensive traits in prey organisms. However, little is known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid phase extraction setup that allows for extraction of exuded metabolites from live copepods. We captured exudates from male and female Temora longicornis and analyzed the content with high resolution LC-MS. Chemometric methods revealed 87 compounds that constitute a specific chemical pattern either qualitatively or quantitatively indicating copepod presence. The majority of the compounds were present in both female and male exudates, but nine compounds were mainly or exclusively present in female exudates and hence potential pheromone candidates. Copepodamide G, known to induce defensive responses in phytoplankton, was among the ten compounds of highest relative abundance in both male and female extracts. The presence of copepodamide G shows that the method can be used to capture and analyze chemical signals from living source organisms. We conclude that solid phase extraction in combination with metabolic profiling of exudates is a useful tool to develop our understanding of the chemical interplay between pelagic organisms.

Keywords: Copepod exudate; Exometabolome; Infochemicals; Metabolomics; Temora longicornis.

Grants and funding

This work was supported by the Danish National Strategic Research Council—IMPAQ—grant no. 10-093522, the Swedish Research Council Formas contract no. 223-2012-693, and EU FP7 ASSEMBLE grant agreement no. 227799. GMN was supported by a Linnaeus grant from the Swedish Research Councils (FORMAS and VR), and the Olle Engkvist Byggmästare Foundation. The Centre for Ocean Life is supported by the Villum Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.