The effects of 5-Hydroxymethylfurfural in mitigating transportation stress of large yellow croaker (Larimichthys crocea)

The stress response induced by the transportation of fish from nearshore cages to aquaculture vessel is a great challenge in open ocean aquaculture. Therefore, the present study investigated the stress mitigatory potency of 5-Hydroxymethylfurfural (5-HMF) during transportation in large yellow croaker (Larimichthys crocea) based on the stress hormones, antioxidant capacity, gill morphology and skin transcriptome. The large yellow croaker (388 ± 58.79 g) were transported for about 2.5 h in rectangular canvas tanks treated with or without 5-HMF (0.2 mg/L). Blood, gill and skin were sampled before the transportation (control, C0), during transportation (treated with/without 5-HMF, EC/TC), upon arrival (treated with/without 5-HMF, E0/T0) as well as 12, 24 and 72 h after transportation (treated with 5-HMF, E12/E24/E72; treated without 5-HMF, T12/T24/T72). Results showed that the serum cortisol, epinephrine and platelet number were significantly elevated in both treatments during transportation and at arrival, while these stress-related parameters tended to be reduced in fish exposed to 5-HMF than those not. Apart from that, transportation also exerted negative effects on osmoregulation, characterized by significantly reduced activity of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase in gill during transportation and early recovery, which was ameliorated by the addition of 5-HMF. Furthermore, the differentially expressed genes in skin of transportation and recovery phase compared with that of pre-transportation were enriched in PI3K-AKT signaling pathway. As a crucial component of this signaling pathway, the hsp90α expression was notably elevated in fish receiving 5-HMF than those not during transportation and early recovery phase. Therefore, the addition of 5-HMF to water at 0.2 mg/L can alleviate the transportation stress and accelerate the recovery process of large yellow croaker, and this mitigatory potency might be mainly achieved by enhancing hsp90α expression to expedite the clearance of misfolded proteins induced by transportation stress.