Metabolomic and physiological insights to ameliorate post-harvest stress in cultured mussels

Survival and quality of Green-lipped mussels (Perna canaliculus) exported live could be further improved through enhanced post-harvest handling, aiming to reduce the physiological stress associated with transport out of water. Addressing these issues requires identifying treatments to reduce post-harvest stress and understanding underpinning molecular mechanisms.

This study aimed to evaluate treatments (low temperature and MgCl₂ anaesthetic baths) to mitigate post-harvest handling stress in mussels.

We analysed metabolomic profiles using gas chromatography-mass spectrometry (GC/MS), anaerobic enzyme activity in gill and adductor muscle, and haemolymph biochemistry (pH, antioxidant capacity and osmolality) in mussels subjected to 14 °C, 4 °C or MgCl₂ water-bath treatments after simulated harvest.

Metabolomic analyses revealed post-harvest mussels experienced increased anaerobic activity, osmotic and oxidative stress, reduced pH (Δ0.31), and lower polyunsaturated fatty acids (PUFA). Mussels immersed in 14 °C seawater recovered from anaerobiosis but had a strong indication of oxidative stress. Although mussels in 4 °C immersion had increased levels of PUFA, implying depressed lipid oxidation, the treatment did not improve recovery from anaerobiosis, indicated by reduced pH (Δ0.38). Mussels treated with MgCl₂ showed some recovery from anaerobic handling stress, with decreased anaerobic end product accumulation and a more modest haemolymph pH decline (Δ0.16) compared to controls. While anaerobic enzyme activities showed tissue-specific responses, they did not exhibit the pronounced differences among treatments shown by their products in metabolic profiling.

Among the proposed re-immersion treatments, immersing mussels in seawater containing 40 g L^- 1 MgCl₂ seemed to be the most effective treatment to alleviate post-harvest metabolic stress, therefore potentially increasing shelf-life of mussels destined for live export.