Abstract
Long-term stock decline in the Japanese eel (Anguilla japonica) is a serious issue. To reduce natural resource utilization in Japan, artificial hormonal induction of maturation and fertilization in the Japanese eel has been intensively studied. Recent experiment on feminized (by feeding a commercial diet containing estradiol-17β for first half year) cultured female eels have shown ovulation problems, which is seldom observed in captured wild female eels. Therefore, the aim of this study is to try to investigate causes of ovulation problem frequently seen in cultured female eels by comparative trans-omics analyses. The omics data showed low growth hormone and luteinizing hormone transcription levels in the brain and low sex hormone–binding globulin transcription levels in the liver of the cultured female eels. In addition, it was found that high accumulation of glucose-6-phosphate and, maltose in the liver of the cultured female eel. It was also found that docosahexaenoic (DHA) acid, eicosapentaenoic acid (EPA) and arachidonic acid (ARA) ratios in cultured female eels were quite different from wild female eels. The data suggested that ovulation problem in cultured female eels was possibly resulted from prolonged intake of a high-carbohydrate diet and/or suboptimal DHA/EPA/ARA ratios in a diet.
Highlights
The Japanese eel (Anguilla japonica) is an important species for inland aquaculture in Japan because of its high economic value
We examined messenger RNA (mRNA) expression of 3-oxo-5-beta-steroid 4-dehydrogenase, cytochrome P450 1A9, and sex hormone-binding globulin because these genes are related to steroidogenesis and steroid transport
We observed the mRNA expression level of akr1d1 was 1.3-fold higher in cultured female eels compared to wild female eels, while cyp1a9 and shbg mRNA levels were 8.9-fold and 6.6-fold higher, respectively, in wild female eels compared to cultured female eels (Fig 2)
Summary
The Japanese eel (Anguilla japonica) is an important species for inland aquaculture in Japan because of its high economic value. The seed used in its cultivation is taken from wild glass eels captured from estuaries. As the glass eel arrival has been drastically dropped since 1970s, eel seed depletion has become a serious problem in Japan and in other East Asian countries. To reduce natural resource utilization in Japan, artificial breeding techniques of eels have been studied, and rearing methods of eel leptocephali have been developed [1].
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call