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Juvenile sablefish, Anoplopoma fimbria (mean length 15.5 ± 1.9 cm, mean weight 68.5 ± 4.8 g), were used to evaluate the effects on growth, oxidative stress, and non-specific immune responses by changes of water temperature (8, 10, 12, 14, 16, 18, and 20 °C) and salinity (100 (35.0), 90 (31.5), 80 (28.0), 70 (24.5), 60 (21.0), 50 (17.5), and 40% (14.0) (‰)) for 4 months. The growth performance was significantly increased at the temperature of 12 and 14 °C, and the feed efficiency was notably decreased at the temperature of 18 °C. The growth performance and feed efficiency were also significantly decreased at low salinity. The antioxidant responses such as superoxide dismutase and catalase were significantly increased by the high temperature and decreased by the low salinity. The immune responses such as lysozyme and phagocytosis were elevated by the temperature of 18 °C and decreased by the salinity of 50%. The results of this study indicate that the growth performance of juvenile sablefish, A. fimbria, is influenced by the temperature and salinity, and the excessive temperature and salinity levels can affect the antioxidant and immune responses.

Myostatin is one of the transforming growth factor (TGF)‐β family members and plays inhibitory roles in the development and growth of muscle in mammals. Mammalian myostatins have been studied intensively, considering its medical and industrial potential use. Still, limited information is available about myostatin homologues in crustaceans. In the present study, we isolated for the first time cDNA that encodes for myostatin‐like protein (Pj‐MSTN) from Morotoge shrimp, Pandalopsis japonica. The putative mature peptide of Pj‐MSTN was composed of 109 amino acids, which contains an additional amino acid residue compared with mammalian myostatins. Pj‐MSTN exhibited 32% amino acid sequence identity and 52% similarity to human myostatin. Multiple sequence alignment analysis indicated that Pj‐MSTN shared the conserved proteolytic cleavage site (RXXR) for its maturation and nine cysteine residues for disulphide bridges. These results suggest that Pj‐MSTN has conserved the three‐dimensional structure of TGF‐β family members in vertebrates. Phylogenetic analysis suggests that Pj‐MSTN is a primitive form of vertebrate myostatin and GDF11. The expression of Pj‐MSTN was not just identified in muscular tissues, suggesting that Pj‐MSTN functions differently from mammalian myostatin. Ablation of the X‐organ/sinus gland complex significantly reduced the expression of Pj‐MSTN in most tissues, suggesting its potential association with moulting.