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<p>The Japanese eel (<i>Anguilla japonica</i>), a species of significant nutritional and economic importance, faces challenges in aquaculture due to its reliance on wild glass eels and a male-biased sex ratio, which limits the production efficiency. We investigated the effects of stocking density on growth performance and sex determination in <i>A. japonica</i> culture with a focus on the role of cortisol as a potential mediator. Using metyrapone, a cortisol synthesis inhibitor, three experimental groups were established: low-density (L, 30 inds./100 L), high-density (H, 60 inds./100 L), and high-density with metyrapone supplementation (HM, 60 inds./100 L+10-mg metyrapone/kg diet). The experimental trial was conducted over a 20-week period. Results reveal that high-density conditions significantly suppressed the growth performance as evidenced by reduced final body weight, length, and feed conversion ratios, while metyrapone supplementation mitigated these effects. Serum cortisol levels were the highest in the H group, whereas growth hormone levels were inversely correlated with cortisol. Gene expression analysis indicated that high-density conditions down-regulated the growth-related genes (<i>ghr1</i>, <i>ghr2</i>, and <i>igf-1</i>), but metyrapone partially restored their expression. Histological examination of gonads showed a significant increase in female eels in the HM group compared to the L and H groups, suggesting that cortisol modulation influenced the sex differentiation and sex ratio. Furthermore, metyrapone up-regulated female-related genes (<i>cyp19a1a</i>, <i>sox3</i>, and <i>figla</i>) and down-regulated male-related genes (<i>gsdf</i>, <i>dmrt1</i>, <i>sox9</i>, and <i>amh</i>). These findings highlight the vital role of cortisol in mediating density-dependent growth suppression and sex determination of <i>A. japonica</i>. This study provided novel insights into stress-mediated mechanisms in the aquaculture and proposed that the cortisol modulation is a potential strategy to enhance the production efficiency and promote sustainable eel farming practices.</p>

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Metyrapone supplementation mitigates cortisol-mediated growth inhibition and sex bias in high-density cultured Japanese eels Anguilla japonica

  • 期刊论文

  • 发表日期：

    2026年2月3日

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  • Bin Xie,
  • Jingwei Liu,
  • Xichen Jin,
  • Xiangbiao Zeng,
  • Ziqian Shen,
  • Yanhe Liu,
  • Kang Li,
  • Liping Liu

摘要

The Japanese eel (Anguilla japonica), a species of significant nutritional and economic importance, faces challenges in aquaculture due to its reliance on wild glass eels and a male-biased sex ratio, which limits the production efficiency. We investigated the effects of stocking density on growth performance and sex determination in A. japonica culture with a focus on the role of cortisol as a potential mediator. Using metyrapone, a cortisol synthesis inhibitor, three experimental groups were established: low-density (L, 30 inds./100 L), high-density (H, 60 inds./100 L), and high-density with metyrapone supplementation (HM, 60 inds./100 L+10-mg metyrapone/kg diet). The experimental trial was conducted over a 20-week period. Results reveal that high-density conditions significantly suppressed the growth performance as evidenced by reduced final body weight, length, and feed conversion ratios, while metyrapone supplementation mitigated these effects. Serum cortisol levels were the highest in the H group, whereas growth hormone levels were inversely correlated with cortisol. Gene expression analysis indicated that high-density conditions down-regulated the growth-related genes (ghr1, ghr2, and igf-1), but metyrapone partially restored their expression. Histological examination of gonads showed a significant increase in female eels in the HM group compared to the L and H groups, suggesting that cortisol modulation influenced the sex differentiation and sex ratio. Furthermore, metyrapone up-regulated female-related genes (cyp19a1a, sox3, and figla) and down-regulated male-related genes (gsdf, dmrt1, sox9, and amh). These findings highlight the vital role of cortisol in mediating density-dependent growth suppression and sex determination of A. japonica. This study provided novel insights into stress-mediated mechanisms in the aquaculture and proposed that the cortisol modulation is a potential strategy to enhance the production efficiency and promote sustainable eel farming practices.