The weak association between hypoxia tolerance and thermal tolerance increases the susceptibility of abalone to...

The simultaneous occurrence of high temperatures and hypoxia events caused mass die-offs of aquatic animals. It is crucial to investigate the relationship between hypoxia tolerance and thermal tolerance of aquatic animals to predict the biological and ecological outcomes under global climate change scenarios. In this study, the hypoxia tolerance and thermal tolerance of Pacific abalone, Haliotis discus hannai, were measured by methods based on adhesion capacity (hypoxia adhesion duration and heat adhesion duration) and heart rate fluctuations (breakpoint of dissolved oxygen and Arrhenius breakpoint temperature). Weak correlations were found between hypoxia tolerance and thermal tolerance (Spearman correlation, r = -0.09, P = 0.2069; Pearson correlation, r = -0.04, P = 0.3313). Furthermore, a total of 21 significant SNPs and 19 candidate genes (such as cubn, lrp6, gria2, rft2, and casp8) were identified to be associated with hypoxia tolerance of Pacific abalone by conducting whole genome resequencing and genome-wide association study (GWAS). But there was no overlap between candidate genes associated with hypoxia tolerance and candidate genes associated with thermal tolerance, validating the weak correlation between hypoxia tolerance and thermal tolerance. This study highlights that individuals with greater hypoxia tolerance do not necessarily have greater thermal tolerance. Global warming and hypoxia may pose a greater threat to population size and genetic diversity of some aquatic animals than previously believed.