Effect of hormone injection frequency on the lipid content and fatty acid compositions in gonad, muscle and liver of Anguilla japonica during artificial maturation

Abstract

Two groups of Anguilla japonica were treated with hormone, one on a weekly basis, the other on a biweekly basis. Intramuscular injection was applied at a dose of 0.75 mg/kg BW carp pituitary extract (CPE) plus 150 IU/kg BW human chorionic gonadotropin (hCG) for female fish, while males received half of this dose. The average total lipid content of the gonads from the weekly treated group, i.e. 20.6 ± 1.2 % for females and 18.0 ± 2.3 % for males, was significantly higher than the biweekly treated group, 16.8 ± 0.7 and 15.5 ± 1.3 %, respectively (p \ 0.05). For both muscle and liver, the readings were not significantly different. The gonads from the weekly treated fish had more fatty acids, particularly saturated fatty acids, polyunsaturated fatty acids, highly unsaturated fatty acids, eicosapentaenoic acid (20:5n-3, EPA), docosahexaenoic acid (22:6n-3, DHA) and arachidonic acid (20:4n-6, ARA). Histological examination showed that the ovaries of both the weekly and the biweekly treated fish were mainly at stage IV. However, the weekly treated females had bigger oocyte diameter (722.0 ± 60.9 lm) than the biweekly females (611.6 ± 22.6 lm). These results suggest that CPE and hCG promoted the maturation process for both scheduled induction and that the frequency of hormone injection influenced the biochemical composition of gonads, especially their lipids. Our study describes for the first time the effect of hormone injection frequency on the lipid content and fatty acid composition in the gonads of A. japonica during artificial maturation.

Lipid profiles of Mediterranean moray, Muraena helena, European conger, Conger conger, and European eel, Anguilla anguilla (Actinopterygii: Anguilliformes)

“…This can be explained by physiology of osmoregulation in marine environment, since marine fish tend to retain water to prevent permanent physiological dehydration in salt water. Also as a consequence of marine origin, moray and conger had higher amounts of inorganic Degani et al 1986) which was also similar for other eel species (Oku et al 2009, Rupia et al 2014). …”

Effects of different dietary DHA:EPA ratios on gonadal steroidogenesis in the marine teleost, tongue sole (Cynoglossus semilaevis)

“…De novo synthesis of EPA and DHA in the liver and probable subsequent transfer of them to the testis was also observed in that study. Differently, Japanese eel ( Anguilla japonica ) testes seemed to have a higher preference for EPA ( 42 ) . In addition, in the muscle of tongue sole the contents of both DHA and EPA were higher in males than in females.…”

Biochemical composition of tropical eel Anguilla bicolor McClelland,1844 in Freshwater and Estuary

“…Eel fish are dissected to be isolated gonads using surgical devices. Gonads are weighted using analytical scales (Explorer O-HAUS) to calculate the value of GSI (Gonadosomatic Index) according to [19].…”