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Tetraploid fish are the key source of diploid gametes in polyploid breeding, and they can be induced by disrupting the first mitotic cell cleavage. In this study, the induction protocol of tetraploid by hydrostatic pressure shock and the viability of the tetraploid progenies were investigated in turbot, Scophthalmus maximus. Under water temperature of 14.5 ± 0.5 °C, fertilized diploid zygotes were treated by different combination of timing (65–90 min after fertilization, maf), pressure intensity (60–85 MPa), and duration (2–10 min), respectively. Ploidy level was determined by silver staining of NOR regions, karyotype analysis, and flow cytometry. The optimal protocol for the pressure shock induction was determined to be the combination of timing of 80 maf, 75 MPa of hydrostatic pressure, and 6 min of duration time. Two batches of tetraploid-induced progenies with a total of more than 73,000 morphologically normal larvae were produced. The hatching rates and tetraploidy rates of the two induction groups were 8.97% and 4.09% and 53.33% and 46.67% at 1 day after hatching (dah), respectively. At 150 dah, 1 out of 20 juveniles was identified as tetraploid by karyotype analysis. However, none of tetraploid juveniles was detected by the flow cytometry analysis among the 446 juveniles survived at 365 dah. This preliminary study provides the evidence supporting the large-scale production of tetraploid turbot progenies, thus encouraging further research on the subject. [ABSTRACT FROM AUTHOR]

Insulin-like growth factors I and II (IGF-I and IGF-II) are important regulators of vertebrate growth and development. This study characterized the mRNA expressions of igf-i and igf-ii during turbot ( Scophthalmus maximus ) metamorphosis to elucidate the possible regulatory role of the IGF system in flatfish metamorphosis. Results showed that the mRNA levels of igf-i significantly increased at the early-metamorphosis stage and then gradually decreased until metamorphosis was completed. By contrast, mRNA levels of igf-ii significantly increased at the pre-metamorphosis stage and then substantially decreased during metamorphosis. Meanwhile, the whole-body thyroxine (T4) levels varied during larval metamorphosis, and the highest value was observed in the climax-metamorphosis. The mRNA levels of igf-i significantly increased and decreased by T4 and thiourea (TU, inhibitor of endogenous thyroid hormone) during metamorphosis, respectively. Conversely, the mRNA levels of igf-ii remained unchanged. Furthermore, TU significantly inhibited the T4-induced mRNA up-regulation of igf-i during metamorphosis. The whole-body thyroxine (T4) levels were significantly increased and decreased by T4 and TU during metamorphosis, respectively. These results suggested that igf-i and igf-ii may play different functional roles in larval development stages, and igf-i may have a crucial function in regulating the early metamorphic development of turbot. These findings may enhance our understanding of the potential roles of the IGF system to control flatfish metamorphosis and contribute to the improvement of broodstock management for larvae. [ABSTRACT FROM AUTHOR]

All-female production will maximize the profit potential for the aquaculture of the turbot Scophthalmus maximus , which exhibits significant sexually dimorphic growth. However, the basis for the technology of all-female production, i.e. the genetic mechanism of sex determination in turbot has been obscure so far, and might be ascertained by analysis of the sex ratio of its diploid mitotic gynogens. In this study, artificial mitotic gynogenesis in turbot was induced by hydrostatic pressure shock of its eggs activated by ultraviolet (UV)-irradiated sperm of red sea bream Pagrus major . Before the activation of turbot eggs, cryopreserved sperm of red sea bream were thawed, diluted 1:20 with Hank's solution, and UV-irradiated at a dosage of 6480–7200 erg/mm 2 . Under water temperature of 14.5 ± 0.5 °C, treatments were tested by shocking the activated eggs at designed protocols: timings of 70–95 maf (min after fertilization) with an intensity of 70 MPa for 6 min; intensities of 60–85 MPa with a timing of 90 maf for 6 min; durations of 2–10 min with an intensity of 75 MPa initiated at 90 maf. The optimal protocol of the induction was determined to be pressure-shocking activated eggs initiated at 85–90 maf with 75 MPa for 6 min. A mitotic gynogen of 124 juveniles survived by 150 days after hatching. The ploidy of these juveniles was confirmed to be diploid by flow cytometry and their sex ratio was 1:1 female to male. The sex ratio of these juveniles supported the assumption of a genetic mechanism of sex determination of female heterogametes (ZW/ZZ) in turbot. This protocol can be used to create homozygous clones of double haploids that are very useful for researches on both the sex determination mechanism and selective breeding of this important farmed fish species. [ABSTRACT FROM AUTHOR]

The article focuses on findings of a study related to molecular components associated with egg quality during the reproductive season of turbot, or Scophthalmus maximus. It states significance of production of quality eggs for producing quality fish larvae and mentions role of vitellogenin (Vtg), a protein associated with yolk formation. It notes that concentration and composition of Vtg is associated with process like oocyte maturation, which further effects egg quality.

This study investigated the growth performance and non-specific immunity in sub-adult turbot fed with graded levels of vitamin E (0, 120, 240, 480 and 960 mg kg −1 ) for 15 weeks. Results showed that the final weight, specific growth rate, nitro blue tetrazolium positive leucocytes of head kidney, phagocytic index, serum lysozyme activity and superoxide dismutase activity significantly increased with increasing vitamin E levels. The highest values were recorded in the diet with 480 mg kg −1 vitamin E. However, no significant differences in the hepatosomatic index, viscerosomatic index and survival rate were found among all dietary treatment. Furthermore, the expression levels of complement component 3 (C3), tumor necrosis factor-α (TNF-α) and interleukine 1β (IL-1β) were significantly upregulated in the fish feed with the vitamin E-supplemented diets. Compared with the basal diet, the diet supplemented with 480 mg kg −1 vitamin E significantly augmented the mRNA expression of IL-1β, TNF-α in the spleen and head-kidney, C3 in the liver, respectively. In conclusion, the obtained results indicate the basal diet supplemented with moderate dietary vitamin E (480 mg kg −1 ) increased the growth, nonspecific immune responses, and expression levels of some immune-related genes in sub-adult turbot. These observations suggest that optimal dietary vitamin E can promote the growth, maintain the health and improve the broodstock management for turbot. [ABSTRACT FROM AUTHOR]

Temperature is a critical abiotic factor in aquaculture farming. Serum cortisol, glucose, respiratory frequency, hepatic glycogen, anti-oxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT], and glutathione peroxidase [GPx]), malondialdehyde (MDA) content, and expression of heat shock proteins (hsp70 , 90) and apoptosis-related genes (p53 , caspase3 , bax , bcl2) of turbot were determined at 27 °C under different thermal durations (0, 6, 12, 24, 48, 72, 96 h) to illustrate the underlying physiological response mechanisms. Results showed that cortisol and glucose significantly increased at 27 °C from 0 h to 12 h, and then dramatically decreased from 24 h to 96 h. Respiratory frequency manifested similar results to cortisol. Hepatic glycogen content, GPx and CAT activities gradually decreased in a time-dependent manner under thermal stress. However, SOD activity significantly increased at 6, 12, 24 h and then decreased until the end of thermal stress. Hepatic MDA content significantly increased from 12 h to 96 h. In addition, the apoptosis rate of hepatocyte gradually increased under thermal stress. p53 , caspase3 and bcl2 mRNAs were significantly up-regulated under thermal stress within 6 h, and down-regulated from 12 h to 96 h. bax mRNA was significantly up-regulated from 0 h to 6 h, and no significant difference was observed from 6 h to 96 h. Hepatic hsp70 and hsp90 mRNAs were significantly up-regulated from 6 h to 12 h, which was similar to those of serum glucose results. These results indicate that hyperthermal stress elevates respiratory frequency, serum cortisol and glucose contents, promotes hepatic glycogenolysis, impairs hepatic antioxidant capacity and induces hepatocyte apoptosis by p53 - bax - bcl2 and the caspase-dependent pathways. These findings expand the current knowledge on thermal tolerance and aid the management of turbot in captivity. • Hyperthermal stress affect respiratory frequency, serum cortisol and glucose levels. • Hyperthermal stress promote hepatic glycogenolysis in a time-dependent manner. • Hepatic antioxidant enzyme activities were modulated during hyperthermal stress. • p53 - bax - bcl2 and caspase-dependent pathways involved in hepatocyte apoptosis. • The transcription of hsp70 and hsp90 were modulated subject to hyperthermal stress. [ABSTRACT FROM AUTHOR]