LAUSR

Lipids play a central role in the metabolism of most organisms. These molecules are paramount during reproduction, when females transfer their internal lipid reserves to build-up oocytes' yolk. The aim of the present study was to understand neutral lipid (NL) dynamics during the embryogenesis of two commercially important crabs, Carcinus maenas (Linnaeus, 1758) and Necora puber (Linnaeus, 1767), using electrospray ionization mass spectrometry (ESI–MS) and tandem MS (ESI–MS/MS). Total lipid extracts were fractionated into NLs and polar lipids (PLs). Triacylglycerol (TAG) profile of NL and fatty acid (FA) profiles of both NLs and PLs were determined in two different embryonic stages: newly-extruded embryos (stage 1, a proxy of maternal investment) and ready-to-hatch embryos (stage 3, a proxy of newly-hatched larvae). In total, 16 molecular species of TAGs and their fatty acyl composition were identified, for the first time in marine invertebrate embryos. During embryogenesis, TAGs bearing C14 to C18 saturated and monounsaturated FAs were preferentially consumed, while TAGs with longer carbon chains and polyunsaturated FAs were selectively retained in the late embryonic stage of both crab species. The analysis of FA profiles revealed that energetic FAs were associated with NLs, while essential FAs were more abundant in PLs. These results evidence the different functions of NLs and PLs as energetic and structural lipids, respectively. The novel approach used in our study provides an unprecedented level of information of lipid dynamics at the molecular level, opening new perspectives in the study of maternal investment and embryogenesis in marine invertabrates.