In Atlantic salmon (Salmo salar) aquaculture, it can be more profitable to produce all-female populations. For this species, all-female populations can be created by crossing normal female broodstock (XX) with masculinised female broodstock (XX, known as neomales). Neo-males are typically produced via the application of an exogenous androgen treatment during the labile period (developmental window where phenotypic sex can be easily reversed). The present study determined the masculinisation rate (at 81 and 240–241 days after treatment, dat) following a single 2-h immersion in 17α-methyldihydrotestosterone (MDHT, 400 μg/L) applied at 19 days post hatch (dph) to an all-female Atlantic salmon population with and without dimethyl sulfoxide (DMSO, 300 ppm) as an adjuvant. The expression of several sex differentiation-related genes was also determined in the control and MDHT groups at 0, 1, 3, 7, 16, 33 and 56 dat. Survival and growth were not significantly different between treatment groups. At 81 dat, the proportion of males in the control, DMSO, MDHT and MDHT+DMSO groups was 5%, 5%, 100% and 100%, respectively. At 240–241 dat, the proportion of males in these groups was 6%, 0%, 82% and 88%, respectively. A small proportion of intersex fish were also observed in the control, MDHT and MDHT+DMSO groups at this time, as were sterile fish in the MDHT and MDHT+DMSO groups. When compared to the control group, significant effects of MDHT on gene expression were not detected before 16 dat. Cytochrome P450, family 19, subfamily A, polypeptide 1a (cyp19a1a) expression was downregulated from 33 dat, whereas anti-müllerian hormone (amh) and gonadal soma-derived factor (gsdf) expression was upregulated from 56 dat in the MDHT group. Forkhead box L2a (foxl2a), r-spondin 1 (rspo1) and sexually dimorphic on the Y chromosome (sdY) expression was unaffected by MDHT treatment during the experimental period. This study provides new insights into the changes in gene expression and gonadal morphology induced in genotypic female Atlantic salmon following an immersion in MDHT. The changes in gene expression observed could be involved in mediating morphological sex reversal, and the temporal scale at which they occurred may have implications for refining the age at which sex reversal treatments should be applied in this species. The findings also showed that similar rates of masculinisation are achieved with MDHT alone or in combination with DMSO.

在大西洋鲑鱼 ( Salmo salar) 水产养殖，生产全雌性种群可能更有利可图。对于该物种，可以通过将正常的雌性亲鱼 (XX) 与雄性化的雌性亲鱼（XX，称为新雄性）杂交来创建全雌性种群。新雄性通常是通过在不稳定期（表型性别可以很容易逆转的发育窗口）应用外源性雄激素治疗产生的。本研究确定了在孵化后 19 天 (dph) 应用 17α-甲基二氢睾酮（MDHT，400 μg/L）单次浸泡 2 小时后的男性化率（处理后 81 天和 240-241 天，dat）。含有和不含二甲基亚砜（DMSO，300 ppm）作为佐剂的全雌性大西洋鲑鱼种群。在 0、1、3、7、16、33 和 56 天，在对照组和 MDHT 组中也测定了几种性别分化相关基因的表达。治疗组之间的存活和生长没有显着差异。在第 81 天，对照组、DMSO、MDHT 和 MDHT + DMSO 组的雄性比例分别为 5%、5%、100% 和 100%。在 240-241 dat，这些组中男性的比例分别为 6%、0%、82% 和 88%。此时在对照组、MDHT 和 MDHT + DMSO 组中也观察到了一小部分双性鱼，MDHT 和 MDHT + DMSO 组中的不育鱼也是如此。与对照组相比，在 16 天前未检测到 MDHT 对基因表达的显着影响。对照组、DMSO、MDHT和MDHT+DMSO组的男性比例分别为5%、5%、100%和100%。在 240-241 dat，这些组中男性的比例分别为 6%、0%、82% 和 88%。此时在对照组、MDHT 和 MDHT + DMSO 组中也观察到了一小部分双性鱼，MDHT 和 MDHT + DMSO 组中的不育鱼也是如此。与对照组相比，在 16 天前未检测到 MDHT 对基因表达的显着影响。对照组、DMSO、MDHT和MDHT+DMSO组的男性比例分别为5%、5%、100%和100%。在 240-241 dat，这些组中男性的比例分别为 6%、0%、82% 和 88%。此时在对照组、MDHT 和 MDHT + DMSO 组中也观察到了一小部分双性鱼，MDHT 和 MDHT + DMSO 组中的不育鱼也是如此。与对照组相比，在 16 天前未检测到 MDHT 对基因表达的显着影响。细胞色素 P450，家族 19，亚家族 A，多肽 1a ( cyp19a1a ) 表达从 33 dat 开始下调，而抗苗勒管激素( amh ) 和性腺体细胞衍生因子( gsdf ) 表达从 MDHT 组的 56 dat 开始上调。叉头盒 L2a ( foxl2a )、r-spondin 1 ( rspo1 ) 和Y 染色体上的性二态( sdY) 表达在实验期间不受 MDHT 处理的影响。这项研究为基因型雌性大西洋鲑鱼浸入 MDHT 后基因表达和性腺形态的变化提供了新的见解。观察到的基因表达的变化可能涉及介导形态学性别逆转，并且它们发生的时间尺度可能对完善应在该物种中应用性别逆转治疗的年龄产生影响。研究结果还表明，单独使用 MDHT 或与 DMSO 组合可实现类似的男性化率。