Journal of Aquaculture Research & Development

Abstract

Time Course Effect of Low Salinity on the Plasma Osmotic Pressure, Ion Concentrations and Na+/K+-ATPase Activity in the Gill of Juvenile Lined Seahorse, Hippocampus erectus

Lin Yang, Ting-Ting Lin, Dong Zhang and Xin Liu

The present study is to evaluate the osmoregulatory ability of the lined seahorse Hippocampus erectus, a valuable species for traditional Chinese medicine. The effect of low salinity (10‰, 15‰, 20‰, 25‰, 32‰ as control) on the plasma osmotic pressure, ions concentration including Na+, K+, Ca2+ and Cl-, and Na+/K+-ATPase (NKA) activity in the gill of the juvenile seahorses was carried out within 96 h. The results show that plasma osmotic pressure and ions concentration down-regulated significantly with the decreasing salinity at 6 h to 12 h and stabilized at 12 h to 24 h after the salinity stress. The isotonic point of the juvenile seahorses was 317.13 m Osm·kg-1 after 96 h transfer, the equivalent of the salinity of 12.05‰, meanwhile, isoionic points of Na+ and Cl- were 96.48 mmol·L-1 and 113.64 mmol·L-1 after 96 h transfer, equivalent to the salinity of 8.82‰ and 10.13‰, respectively. Moreover, the gill NKA activity also down-regulated significantly with the decreasing salinity and reached the lowest value at 12 h to 24 h after transfer to hypotonic water, then stabilized even elevated at 48 h. Juvenile H. erectus, is able to stabilize the osmotic pressure and ions concentration at a short time (12 h) after the salinity stressing, suggesting that the species have a strong osmoregulation ability. Moreover, the isotonic point, the equivalent of the salinity of 12.05‰, combined with the gill NKA activity recovered at 24 h after the salinity stress at the salinity of 15‰ and our previous survival and growth data, implying that the juvenile seahorse could be cultured optimally at salinities of 10‰ to 15‰.