Effects of heat shock protein 70 knockdown on the tolerance of the brine shrimp Artemia franciscana to aquaculture-related stressors: Implications for aquatic animal health and production

Abstract

Temperature, pH, salinity and ammonia stress adversely affect the performance and well-being of aquatic organisms, especially those used in aquaculture, a major food production sector. Management strategy to mitigate stress caused by abiotic factors in farmed aquatic organisms is scarce but is highly warranted considering the negative impact of these factors on the welfare and economic production of the farmed animals. The induction of heat shock proteins, mainly 70 kDa Hsp (Hsp70), in farmed fish and shellfish, including the live feed brine shrimp Artemia franciscana, by exposure to a non-lethal heat shock (NLHS) of 37 °C for 30 min followed by 6 h recovery period caused a significant improvement in the tolerance of the animals towards subsequent challenge with an abiotic stress. Although the protective effect of NLHS was associated with enhanced Hsp70 accumulation in these species, the induction of other members of Hsp and their collective involvement in the stress tolerance could not be ignored. This triggered an argument as to whether only Hsp70 or its combination with other Hsps was responsible for inducing stress tolerance phenotype in these species. In this study, we employed RNAi technology in the biological model organism Artemia to gain insight into the functional role of Hsp70 in stress tolerance. The results showed that upon exposure to a NLHS, the wild-type Artemia nauplii capable of producing Hsp70 exhibited significantly higher survival than the unexposed control in all the abiotic stress tolerance tests performed in this study. However, the Hsp70-deficient mutant nauplii did not exhibit increased stress-tolerant phenotypes as the survival percentage of the nauplii decreased by 29, 19, and 15%, respectively, upon challenge with a median lethal concentration of salinity, pH, and ammonia. These results suggest that Hsp70 was involved in inducing tolerance against stress caused by the abiotic factors, and hence can be a potential target for developing strategies to protect economically important aquaculture species from environmental disturbances.