Survival rate and oxygen consumption patterns with respect to salinity changes in juvenile abaloneHaliotis discus hannai

Abstract

The effects of salinity tolerance on survival and oxygen consumption were examined in the abalone Haliotis discus hannai with changes in water temperature and salinity in an indoor rearing system. The survival rate of the control group at 15°C was 100% (Expt. I, 35 psu). In Expt. II, changing the salinity from 35→30→25→20→15 psu, the survival rates were 100 ± 0.0, 100 ± 0.0, 100 ± 0.0, 98.3 ± 2.9, and 95.0 ± 0.0%, respectively. In Expt. III, for salinities of 35→25→15 psu, the rates were 100 ± 0.0, 100 ± 0.0, and 32.5 ± 2.0%, respectively. In Expt. IV, with a sharp salinity change from 35→15 psu, the rates were 100 ± 0.0 and 20.0 ± 2.9%, respectively. The average oxygen consumption at 15°C was 137.6 ± 0.5 mg O 2 /kg/h in Expt. I. In Expt. II, the oxygen consumption decreased gradually from 136.7 ± 2.0 to 103.2 ± 3.5 to 96.9 ± 3.2 to 88.7 ± 4.5 to 82.9 ± 3.6 mg O 2 /kg/h, respectively. Abalone in Expt. III showed the same tendency (i.e., 134.4 ± 1.5, 111.2 ± 3.4, and 93.2 ± 6.1 mg O 2 /kg/h, respectively). In Expt. IV, the oxygen consumption decreased from 141.4 ± 4.0 mg O 2 /kg/h at 35 psu to 99.0 ± 7.7 mg O 2 /kg/h at 15 psu. The tendency was the same in the experiments conducted at 20 and 25°C. Survival was reduced at salinities below 20 psu, and the mortality rate of abalone increased with a sudden salinity change and at high water temperatures.

Transcriptome analysis reveals fluid shear stress (FSS) and atherosclerosis pathway as a candidate molecular mechanism of short-term low salinity stress tolerance in abalone

“…From previously reported studies, we understand how abalone adapts to environmental salinity changes by maintaining their osmotic pressure balance, which is achieved via regulation of their intracellular ions, hemolymph free amino acids, and changes in ion-regulatory genes expression [ 6 – 8 ]. Furthermore, abalone achieves salinity adaptation through modulation of the heart rate by adjusting oxygen consumption and respiratory metabolism [ 5 , 15 ]. Moreover, immune defense is accomplished via the regulation of antioxidant genes and the employment of hemolymph parameters like phagocytosis and respiratory burst [ 7 , 9 ].…”

“…Particularly, abalones on farms in the coastal and inner bays could experience prolonged low salinity conditions due to freshwater intrusion [ 3 , 4 ]. Moreover, abalone encounters a sudden drop in seawater salinity during severe summer rainstorms and typhoon events [ 5 ]. However, changes in ambient salinity could significantly affect abalone inflammatory and immune responses and are associated with several other physiological responses, such as disrupting electrolyte equilibrium, oxidative damage, and metabolism disorders [ 6 – 9 ], which eventually influence their survival and growth [ 10 , 11 ].…”

“…Understanding the mechanism of low salinity tolerance is of great importance to the abalone aquaculture industry, as this would help in the future breeding of more stress-resilient abalone species. Previous studies on salinity adaptation in abalone focused on osmotic and ionic regulation, oxygen consumption, energy metabolism, and cardiac performance [ 5 – 8 , 12 ]. Flow cytometry has also been adopted at the cellular level to assess abalone’s immune competence following salinity stress exposure [ 9 ].…”