The effects of inbreeding on stress resistance of the Pacific oyster Crassostrea gigas at different temperatures and salinities

ABSTRACT The Pacific oyster (Crassostrea gigas) is a commercially important shellfish widely cultured worldwide. Understanding the effect of inbreeding on C. gigas is critical to the long-term feasibility of breeding programmes, especially when selected lines are developed in hatcheries with limited effective population sizes. The effect of inbreeding on stress resistance in C. gigas remains to be explored. The present study evaluated the physiological and immune responses to different temperatures (16–36°C) and salinities (20–40 psu) in an inbreeding line and a wild population of C. gigas. Two physiological parameters, including ammonia-N excretion rate (AER) and oxygen consumption rate (OCR), and three enzyme activities including superoxide dismutase activity (SOD), catalase activity (CAT), and contents of malondialdehyde (MDA) were measured on day 14 of the temperature and salinity exposure. Compared with the wild population, the physiological parameters (AER and OCR) were significantly lower, and the enzyme activities (SOD, CAT, and MDA) were significantly higher in the inbreeding line at suboptimal temperatures or salinities. These results showed that inbreeding has negative effects on stress resistance in C. gigas. In addition, multiple groups with different inbreeding levels would be needed to quantify the effects of inbreeding on stress resistance in C. gigas. KEY POLICY HIGHLIGHTS This is the first study to examine the effect of inbreeding on the stress resistance of C. gigas under temperature and salinity challenges. Inbred oysters showed an equally good performance as wild oysters under benign conditions. The potential disadvantages of inbred oysters in adaptive capacity were shown at suboptimal conditions.