Broadening the adaptation of Sepia pharaonis to low salinity through a graded salinity reduction approach

Abstract

Sepia pharaonis, commonly known as the pharaoh cuttlefish, is a valued cephalopod in aquaculture. However, its sensitivity to salinity fluctuations has constrained its cultivation, especially in regions with varying salinity and during rainy seasons. To address this, our study implemented a graded salinity reduction approach, enabling S. pharaonis to acclimate to an environment with a salinity of 20. Despite a reduction in growth parameters such as mantle length and body weight in the Low-Salinity Acclimation group (LSA), the survival rates were largely consistent with the control group. After the acclimation process, the LSA group demonstrated a strikingly high survival rate of nearly 100% in salinity ranges from 18 to 24, a span previously thought to be deadly for non-acclimated S. pharaonis. Our evaluations indicate that the serum osmotic pressure and ion concentration of S. pharaonis decline with decreasing seawater salinity. During this process, there were significant alterations in the Na+/K+-ATPase activity and the content of free amino acids, suggesting their crucial role in low-salt osmoregulation. Overall, this study not only highlights the potential of the graded salinity reduction method to enhance the adaptability of S. pharaonis to fluctuating salinities, but also underscores the potential of graded salinity reduction as an innovative approach to enhance the resilience of aquaculture species.