Recovery of gill and hepatopancreas tissues in Penaeus vannamei during long-term exposure to high alkalinity following damage induced by abrupt alkalinity increase

The aim of this work was to evaluate growth performance and tissue restoration in the gill and hepatopancreas of juvenile Penaeus vannamei during long-term exposure to high alkalinity following damage induced by an abrupt increase in alkalinity. A 30-day experiment was conducted using four experimental groups with three replicates each: T120 (control), T200, T300, and T400, where alkalinity was maintained at 120 mg CaCO₃/L in T120 and abruptly increased to 200, 300, and 400 mg CaCO₃/L, respectively, using sodium bicarbonate (NaHCO₃). Juveniles (n = 336; 1.5 ± 0.8 g) were stocked at 28 shrimp/m² in 60 L tanks with filtered seawater. Tanks were continuously aerated, and water temperature was maintained at 27 ± 1 °C. Shrimp were fed a commercial diet (35% crude protein) four times daily. On day 30, shrimp were counted and weighed to assess survival and growth-related parameters. Histological samples were taken on days 0, 14, and 30. No differences in growth performance were observed among experimental groups. Histological changes were observed in T200 and T300, which were reversed over time. In contrast, T400 shrimp exhibited severe damage to both the gills and hepatopancreas, with partial recovery of the hepatopancreas noted after 30 days. This work highlights the resilience of P. vannamei in coping with elevated alkalinity levels and demonstrates the capacity for significant recovery of gill and hepatopancreas tissues following high alkalinity-induced stress.