Solid phase extraction and metabolic profiling of exudates from living copepods

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.

Distinctly different behavioral responses of a copepod, Temora longicornis , to different strains of toxic dinoflagellates, Alexandrium spp.

“…On the other hand, behavioral response of T. longicornis to three PST-producing strains, even when acknowledging their differences in total amounts and PST profile, was too different to accept a universal role of PSTs in affecting T. longicornis feeding, and other substances may provide the cues for the diverse behavioral responses observed here. One promising avenue to pursue may be to combine directly observed responses with metabolic profiling of the phytoplankton as applied to resolve other plankton chemical cues (Selander et al, 2016).…”

Crustacean zooplankton release copious amounts of dissolved organic matter as taurine in the ocean

“…In this study we focused on concentrations and the direct release of dissolved free Tau, but Tau can also occur conjugated with a variety of organic acids. For example, Tau-bearing lipids were found in the metabolites and release products of various copepod genera, which tend to accumulate these compounds under starvation (Mayor et al 2015;Selander et al 2015Selander et al , 2016. Consequently, it is reasonable to assume that in the deep ocean, where food is limited and temperature low, zooplankton accumulate dissolved free Tau and Tau-conjugated compounds.…”

Marine Metabolomics: a Method for Nontargeted Measurement of Metabolites in Seawater by Gas Chromatography–Mass Spectrometry

“…For instance, in terrestrial and limnic systems, researchers used exometabolomics to study soil organic matter cycling (6, 7), overflow metabolism of cultivable microorganisms (8, 9), and chemical ecology of the environment (10, 11). While intracellular metabolomic analyses of tissues from marine microbial cells to invertebrates are becoming increasingly more common (12–14), the defining characteristic of marine habitats, i.e., high salt concentration, limits exometabolomic analyses of the oceans to studies that require salt removal prior to metabolite extraction (10, 15, 16).…”