ABSTRACT. Sturgeons (Acipenser schrenckii) are of high evolutionary, economic, and conservation value, and caviar isone of the most valuable animal food products in the world. The Illumina HiSeq2000 sequencing platform was used to construct testicular and ovarian transcriptomes to identify genes involved in reproduction and sex determination in A. schrenckii. A total of 122,381 and 114,527 unigenes were obtained in the testicular and ovarian transcriptomes, respectively, with average lengths of 748 and 697 bp. A total of 46,179 genes were matched to the nonredundant nr database. GO (31,266), KEGG (39,712), and COG analyses (20,126) were performed to identify potential genes and their functions. Twenty-six gene families involved in reproduction and sex determination were identified from the A. schrenckii testicular and ovarian transcriptomes based on functional annotation of non-redundant transcripts and comparisons with the published literature. Furthermore, 1309 unigenes showed significant differences between the testes and ovaries, including 782 genes that were up-regulated in the testes and 527 that were upregulated in the ovaries. Eleven genes were involved in reproduction and sex determination mechanisms. Furthermore, 19,065 simple sequence repeats (SSRs) were identified in the expressed sequence tagged dataset, and 190,863 and 193,258 single nucleotide polymorphisms (SNPs) were obtained from the testicular and ovarian transcriptomic databases, respectively. This study provides new sequence information about A. schrenckii, which will provide a basis for the further study of reproduction and sex determination mechanisms in Acipenser species. The potential SSR and SNP markers isolated from the transcriptome may shed light on the evolution and molecular ecology of Acipenser species.

Exogenous glutamine (Gln) was evaluated for its effect on antioxidation and serum non-specific immunity in juvenile Hybrid sturgeon (Acipenser schrenckii $ · Huso dauricus #). Seven basal diets supplemented with 0.0, 0.3, 0.6, 0.9, 1.2, 1.5% of Gln and 1.0% alanyl-glutamine (Aln-Gln) were fed to fish (initial mean weight: 22.38 ± 0.18 g) for 8 weeks, and the experiment was conducted in triplicate. Treatment of fish supplemented with 1.2, 1.5% of Gln, or 1.0% of Aln-Gln caused a significantly higher glutathione peroxidase (GPX), superoxide dismutase (SOD) activities, and glutathione (GSH) content, and lower serum malondialdehyde (MDA) levels (P < 0.05) in serum, hepatopancreas and muscles. The addition of 0.9% Gln significantly improved the serum complement-3 (C3) and complement-4 (C4) levels (P < 0.05). These findings suggest that diet supplementation with 0.9-1.2% Gln or 1.0% of Aln-Gln may enhance the activity of the antioxidant defense system and the serum non-specific immunity of juvenile Hybrid sturgeon.

The histological developments of the gonad and the associated sex steroid levels were determined in the breeding stocks of Acipenser schrenckii (age classes 1 to 5) maintained under natural temperature regimes (December 4°C; August 26°C). Early sex differentiation was observed in 1-year-old fish, while testosterone (T) and 17b-estradiol (E 2 ) levels ranged from T 1.1 to 3.4 nmol l )1 (average 1.8 nmol l )1 ), and E 2 varied from 24 to 85 pmol l )1 (av. 50.3 pmol l )1 ). Gonadal status of 2-year-old males was in stage II while ovaries were at stage I, exhibiting T levels from 1.2 to 4.4 nmol l )1 (av. 2.2 nmol l )1 ), and E 2 concentrations from 10 to 97 pmol l )1 (av. 38.9 pmol l )1 ). At the age of 3 years, the testes in males were at developmental stage III while the ovaries remained in stage I, with T levels ranging from 1.3 to 21.7 nmol l )1 (av. 9.6 nmol l )1 ), and E 2 concentrations ranging from 17 to 108 pmol l )1 (av. 44.8 pmol l )1 ). At the age of 4 years, testes in males were at developmental stage III while ovaries in females had reached stage II, with T concentrations ranging from 7.3 to 52.6 nmol l )1 (av. 26.3 nmol l )1 ), and E 2 levels between 13 and 86 pmol l )1 (average 55.3 pmmol l )1 ). In 5-year-old fish, the testes reached maturity stage while the ovaries were mostly in stage III, with T values from 5.7 to 44.2 nmol l )1 (av. 13.9 nmol l )1 ), and E 2 concentrations from 21 to 453 pmol l )1 (av. 137.7 pmol l )1 ). Data demonstrated large differences in sex steroid levels among immature Amur sturgeon, and testicular maturation occurred earlier than ovarian maturation.

The objective of the study was to assess the changes of vitellogenin (Vg) during the course of the reproductive cycle in Amur sturgeon (Acipenser schrenckii). Vg was purified from the serum of vitellogenic female Amur sturgeon by distilled water and gel filtration. Vg had an apparent molecular mass of 410 kDa and appeared as one band corresponding to 205 kDa after SDS-PAGE under reducing conditions. These bands were immunoreacted in Western blotting using antiserum against amur sturgeon lipovitellin (anti-Lv) which is an egg yolk protein derived from Vg. Lv was purified from egg extracts by ammonium sulfate solution and gel filtration. Vg was confirmed to be a lipoglycophosphoprotein by staining with Red oil, Molecular ProesÕ Pro-Q Ò Emerald 300 Glycoprotein Gel stain and Pro-Q Ò Diamond Phosphoprotein Gel Stain. Vg induction was detected after injection of E 2 at a concentration of at least 0.5 mg kg )1 , and the plasma Vg concentration was increased by injection of the animals to 0.5 mg kg )1 for 5 day late. Immature sturgeons at 1015 g weight do not naturally synthesize Vg, but strongly responded to exogenously added E 2 . In addition, if they were not stimulated with exogenous E 2 , the youngest sturgeons did not show any detectable amount of Vg in their plasma, suggesting that Amur sturgeons with a body mass range of 903-1015 g could be used for the induction test, irrespective of their sex. The Enzyme-linked immunosorbant assay for sturgeon vg was developed to quantify serum Vg, using purified sturgeon Vg and anti-Vg. The measurable range was from 16.25 to 1000 ng ml )1 . The dilution curve in ELISA of vitellogenic female serum was parallel to the standard curve of purified Vg. The coefficient variations of intra-and inter-assay were less than 5%, respectively. Vg levels varied throughout natural vitellogenesis from 0 lg ml )1 (1-3 years old) to approximately 200 lg ml )1 (7-8 years old). We observed an early transitory peak of serum Vg levels 200 lg ml )1 (for 10 months) at the time of early vitellogenesis and high Vg levels 218 lg ml )1 (for 3 months) in spring period before ovulation. It appears that the duration of vitellogenesis in Amur sturgeon is lasting more than 2 years.

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