Molecular marker is useful in the development of testicular cells transplantation for detecting donor-derived germ cells in the recipient gonad. In this study, a giant gourami (Osphronemus goramy) vasa-like gene (GgVLG) was cloned and characterized for use as a molecular marker for germ cells in this species. Nucleotide sequence analysis revealed that GgVLG comprises 2,340 bps with an open reading frame of 1,962 bps encoding 653 amino acids. The deduced amino acid sequence contained 17 arginine-glycine or arginine-glycine-glycine motifs and eight conserved motifs belonging to the DEAD-box protein family. The GgVLG sequence showed high similarity to Drosophila vasa, common carp vasa homolog and tilapia vasa homolog for 66.2, 85.9, and 90.7%, respectively. In adult tissues, the GgVLG transcripts were specifically detected in ovary and testis. In situ hybridization analysis showed that GgVLG mRNA was detected in oocytes of the ovary and spermatogonia of the testis. There was no signal detected in the spermatocytes, spermatids and other gonadal somatic cells. Thus, consensus sequences, specific localization of GgVLG mRNA in the germ cells, amino acid sequence similarity and phylogenic analysis all suggest that GgVLG is the giant gourami vasa-like gene. Further, GgVLG can be used as a molecular marker for giant gourami germ cells.

Transgenic has been known as one of the applicable methods to improve growth performance of cultured fish. This study was performed to evaluate the growth performance, survival, and body composition of the 3rd generation of growth hormone (GH) transgenic common carp (TG). Juveniles (BW: 1.53 ± 0.03 g) were reared for 60 days in 250-L glass aquarium with stocking density of 25 fishes/aquarium. Fishes were fed with commercial feed (protein content 36%), three times a day to satiation. Growth and survival were measured every 20 days. Our results showed that TG fish has 1.49 times higher in average weight growth (p < 0.05) compared with the non-transgenic common carp (NT). Higher total feed consumption, survival, body protein content, protein and lipid retention, hepatosomatic index, and lower feed conversion ratio were also shown on TG fish compared with NT fish (p < 0.05). However, body lipid content and blood glucose level of TG fish were lower (p < 0.05) compared with the NT fish. Total ammonium nitrogen level in rearing media of TG fish was 51.78% lower (p < 0.05) than that of the NT fish. In conclusion, culturing of GH-TG common carp showed potential to achieve high productivity, efficient, and environmental-friendly aquaculture.

Eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have important nutritional benefits in humans. EPA and DHA are mainly derived from fish, but the decline in the stocks of major marine capture fishes could result in these fatty acids being consumed less. Farmed fish could serve as promising sources of EPA and DHA, but they need these fatty acids in their diets. Generation of fish strains that are capable of synthesizing enough amounts of EPA/DHA from the conversion of α-linolenic acid (LNA, 18:3n-3) rich oils can supply a new EPA/DHA source. This may be achieved by over-expression of genes encoding enzymes involved in HUFA biosynthesis. In aquaculture, the successful of this technique would open the possibility to reduce the enrichment of live food with fish oils for marine fish larvae, and to completely substitute fish oils with plant oils without reducing the quality of flesh in terms of EPA and DHA contents. Here, three genes, i.e. Δ6-desaturase-like (OmΔ6FAD), Δ5-desaturase-like (OmΔ5FAD) and elongase-like (MELO) encoding EPA/DHA metabolic enzymes derived from masu salmon (Oncorhynchus masou) were individually transferred into zebrafish (Danio rerio) as a model to increase its ability for synthesizing EPA and DHA. Fatty acid analysis showed that EPA content in whole body of the second transgenic fish generation over-expressing OmΔ6FAD gene was 1.4 fold and that of DHA was 2.1 fold higher (P<0.05) than those in non-transgenic fish. The EPA content in whole body of transgenic fish over-expressing OmΔ5FAD gene was 1.21-fold, and that of DHA was 1.24-fold higher (P<0.05) than those in nontransgenic fish. The same patterns were obtained in transgenic fish over-expressing MELO gene. EPA content was increased by 1.30-fold and DHA content by 1.33-fold higher (P<0.05) than those in non-transgenic fish. The results of studies demonstrated that fatty acid content of fish can be enhanced by over-expressing gene encoding enzymes involved in fatty acid biosynthesis, and perhaps this could be applied to tailor farmed fish as even better sources of valuable human food.