Fig. 1

The difference of Songpu mirror carp and Barbless carp in cold tolerance and cold acclimation. a Lateral views of Songpu mirror carp (upper) and Barbless carp (below) at 15 dpf. b Schematic presentation of the experiments for cold tolerance (acute stress in red line, AS) and cold acclimation (CA in black). Carp larvae at 9 dpf in AS group were directly transferred from normal rearing temperature (28 °C) to lethal cold stress (10 °C) or extreme lethal cold stress (8 °C) for 24 h. Carp larvae at 9 dpf in CA group were transferred from normal rearing temperature (28 °C) to mild low temperature (18 °C) for 24 h followed by exposure to lethal cold (10 °C) or extreme lethal cold (8 °C) for 24 h. Then, cold-treated larvae were recovered at 28 °C for 24 h and survival rates of larvae in AS and CA groups were calculated at 12 dpf. Larvae in AS and CA groups were quickly sampled at 10 dpf (pointed by red and black arrows) for total RNA isolation and served as the control (Ctrl) and cold acclimation (CA) groups of RNA-seq analysis, respectively. c Survival rates of Songpu mirror carp and Barbless carp at 12 dpf in AS groups. d Survival rates of Songpu mirror carp and Barbless carp at 12 dpf in CA groups. **, p < 0.01