Characterizing the metabolic actions of natural stresses in the California red abalone, Haliotis rufescens using 1H NMR metabolomics

Withering syndrome in California red abalone (Haliotis rufescens) is caused by the Rickettsiales-like prokaryote (WS-RLP) Candidatus Xenohaliotis californiensis. WS-RLP infection is not sufficient to cause withering syndrome, and for reasons not yet well understood additional stressors such as elevated water temperature appear to influence disease development. Using nuclear magnetic resonance (NMR) based metabolomics, we have investigated the influence of food availability, temperature, and bacterial infection, both individually and in combination, on the metabolic status of the red abalone. Food limitation caused dramatic reductions in all observed classes of foot muscle metabolites, while at the same time metabolite levels within the digestive gland were preserved or increased. We also found that food limitation in combination with elevated temperature led to greater metabolic perturbations in both tissue types than those observed under food limitation alone. WS-RLP infection and food-limitation resulted in many of the same metabolic changes within the tissues studied, although the effects of infection were less severe. We observed increased levels of homarine in the digestive gland of both food-limited and WS-RLP-infected animals, yet only observed increased homarine levels in the foot muscle of infected abalone. These results further support the recently established glucose-to-homarine ratio in foot muscle as a potential marker for differentiating WS-RLP-infected animals from those of both healthy and food limited abalone. Furthermore, we found that the NMR metabolic data correlates well with histological measurements supporting the use of the metabolomics approach for characterizing both normal and pathological events in marine species, particularly during periods of environmentally relevant stress.