Effects of temperature change on physiological and biochemical responses of Yesso scallop, Patinopecten yessoensis

Water temperature can be a significant environmental stressor that affects the physiological and biochemical responses of mollusks. Yesso scallop, Patinopecten yessoensis, is influenced by water temperature fluctuations caused by the Northern Yellow Sea Cold Water Mass. Here, the effects of acute seawater temperature change, gradual temperature change, and fluctuating temperature on the physiological and enzymatic activities in Yesso scallop were studied. Scallops were transferred directly from rearing temperature (15 °C) to 5, 10, or 20 °C for the acute water temperature change treatment. Scallops in the gradual water temperature change treatment were acclimated to different temperatures (5, 10, and 20 °C) by increasing or decreasing seawater temperature progressively (1-2 °C/day). The results showed that oxygen consumption and ammonia-N excretion rates in the 20 °C-acute water temperature change treatment were significantly higher than those in the gradual treatment (one-way ANOVA, P < 0.01). However, scallop ingestion rate decreased significantly in response to an acute water temperature decrease from 15 to 5 °C, compared with equivalent groups exposed to a gradual temperature drop (one-way ANOVA, P < 0.01). Moreover, hepatopancreatic superoxide dismutase (SOD), catalase (CAT), acid phosphatase (ACP), and lysozyme (LSZ) activities reached their highest levels in the 20 °C-acute treatment after 12 h. Malondialdehyde (MDA) content increased significantly following the acute water temperature changes and reached the highest level in 10 °C-acute treatment after 72 h. Heat shock protein70 gene (Hsp70) expression levels also increased significantly when water temperature was increased rapidly from 15 to 20 °C or decreased rapidly from 15 to 10 °C (P < 0.01). In the fluctuation treatment, seawater temperature was altered every 12 h for a total of six fluctuations. Scallops were transferred directly from 15 to 7 °C (first fluctuation), moved from 7 to 15 °C for the next 12 h (second fluctuation), and then transferred from 15 to 7 °C again (third fluctuation) and so on. As results, significant increases in SOD and CAT activities and MDA content, and decreases in ACP and LSZ activities were observed (one-way ANOVA, P < 0.01). Significantly upregulated Hsp70 expression was also found in hemocytes, gills, and the adductor muscle of scallops in the fluctuating temperature treatment (one-way ANOVA, P < 0.01). In conclusion, acute water temperature changes and fluctuations impacted the physiological and enzymatic activities of Yesso scallops and upregulated Hsp70 expression.