Metabolic changes associated with live transport stress of Haliotis rubra abalone.

Transport stress significantly influences the well-being and survival of abalone, yet the underlying metabolic changes and physiological responses associated with this stress remain poorly understood. To gain comprehensive insights into the metabolic changes and physiological responses of abalone (Haliotis rubra) under transport stress, we conducted a targeted liquid chromatography-mass spectrometry (LC-MS) metabolomics investigation on haemolymph and gill samples collected at different time points, including post-harvesting (pre-transport), post-transport and post-immersion (water holding period) and post-live exporting transport. The results revealed 143 and 141 metabolites that were significantly different among sampling times in haemolymph and gill, respectively. Notably, most of the metabolite differences occurred between the post-transport and post-immersion times, which indicate the strong impacts of transport stress on abalone metabolism. Interestingly, certain metabolites, such as lactic acid, succinic acid, L-hydroxyglutaric acid, uric acid, and myo-inositol, showed time-dependent increases during transport, suggesting their potential as stress biomarkers in abalone. Moreover, abalone that were acclimatized in holding tanks exhibited lesser metabolic changes compared to non-acclimatized, despite both groups being transported with oxygen supply. This highlights the significance of acclimatization and oxygen supply in reducing stress for abalone during transport. Enrichment analysis on abalone samples at 24 h post-transport compared to 96 h post-immersion identified 12 significantly impacted pathways in haemolymph and 34 pathways in gill tissues, indicating a range of metabolic disturbances in transported abalone, such as energy-related pathways, amino acid metabolisms, carbohydrate metabolisms, vitamin metabolisms, oxidative stress, and others. These results offer valuable insights into the physiological responses of abalone to transport stress, guiding improved transport practices to ensure good quality of products arriving at their market destinations.