붉바리(Epinephelus akaara) 장거리 수송을 위한 적정수온 구명

Abstract

Red-spotted grouper Epinephelus akaara has been drawing more attention as one of the potential mariculture fish in Korea. To study the physiology associated with its culture and long-distance transport, we evaluated the changes in blood composition in red-spotted grouper at different water temperature (12℃, 15℃, 18℃ and 21℃). The biochemical characteristics of the blood in experimental fishes were analyzed upon exposure at each temperature condition for 48hr. Physiological parameters investigated were hematocrit (Ht), hemoglobin (Hb), plasma cortisol and glucose, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), NH3, osmolality and total protein (TP), respectively. While little difference was observed in total protein among the experimental group, levels of Ht and Hb, AST and ALT, NH3 and osmolality were increased upon exposure to 12℃. Levels of the plasma cortisol and glucose were also increased at 12℃ as compared to 21℃ group. The result suggests that critical lower limit for red-spotted grouper is 12℃. For molecular analysis, heat shock protein 70 (Hsp 70) was identified from red-spotted grouper (Epinephelus akaara). The cDNA of red-spotted grouper Hsp70 (designated RgHsp70) was cloned by rapid amplification of cDNA ends (RACE). The full-length of RgHsp70 cDNA was 2,152 bp, consisting of a 5’-terminal untranslated region (UTR) of 105 bp, 3’-terminal UTR of 274 bp, and an open reading frame (ORF) of 1,773 bp encoding a polypeptide of 590 amino acids. RgHsp70 contained all the three classical Hsp70 family signatures with a theoretical molecular weight of 64.94 kDa and an estimated isoelectric point of 5.20. Multiple alignment and phylogenetic analysis revealed that RgHsp70 gene shared a high similarity with other Hsp70 genes in fish. RgHsp70 mRNA was predominately expressed in the liver together with a reduced expression in head-kidney tissue. Expression of RgHsp70 in livers was gradually increased as compsure temperature was changed 21 ℃ to 12 ℃. In this study, we investigated the effects of lower water temperature on physiological conditions of a novel red-spotted grouper and found that heat shock protein 70 may be an important molecule involved in immune response.