Lipid Incorporation During Experimental Decay of Arthropods
Laboratory decay experiments were carried out on shrimps, scorpions and cockroaches to monitor changes in the chitin-protein of the arthropod cuticle and associated lipids. The cockroach and scorpion exoskeleton remained largely unaltered morphologically, but the shrimp experienced rapid decomposition within a month that progressed through the 44 week duration of the experiment as revealed by electron microscopy. Mass spectrometry and 13C NMR spectroscopy revealed the association of an n-alkyl component with labile lipids, such as fatty acids with up to 24 carbon atoms, which were incorporated into the decaying macromolecule. The scorpion and cockroach cuticle did not reveal the incorporation of additional lipids indicating that decay is important in initiating in situ lipid association. This experiment provides evidence that lipids can become associated with carbohydrate and proteinaceous macromolecules during the very early stages of decay representing the first stage of the transformation process that contributes to the aliphatic rich composition ubiquitous in organic fossils and in kerogens.