Turbot (Scophthalmus maximus) is an important marine fish both in Europe and North China. Although there are plenty of studies on the reproduction of turbot, the complete cytological process of spermatogenesis remains unclear. In this study, we investigated the submicroscopic structure of total 23 types of male germ cells throughout the breeding season, with a relatively complete process of the primary spermatocytes. We found that the spermatid tail formed early at Spermatid II, and there were at least 16 spherical mitochondria in the spermatozoa. The hepatosomatic index (HSI) and gonadosomatic index (GSI) both peaked during the breeding season. Preliminary analysis showed that the vitality of mature sperm was negatively correlated with the proportion of sperm deformity. The serum 3,5,3′-triiodothyronine (T3), 5-hydroxytryptamine (5-HT), testosterone (T), 17α,20β-Dihydroxy-4-pregnen-3-one (17α,20β-DHP), and 17β-estradiol (E2) all increased during the maturity period, with the change of T content most noticeable. Whereas in the testis, an overall high level of 11-ketotestosterone (11-KT) was more remarkable. The expression and localization of androgen receptor (AR) mRNA showed that the AR was highly expressed at the stages of II (15 – 70 g), with a slight rebound at the mature stages [IV(2200 g) to V(2500 g)], whose change was ahead to the changes of T and 11-KT. Fluorescence in situ hybridization (FISH) analysis showed that the AR mainly distributed in but not limited to Sertoli cells. This study represents the most complete overview of the reproductive cycle and spermatogenesis of turbot, which provides an important reference for the reproduction research and the guidance of flatfish breeding.

中文翻译：

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深入了解水产养殖多鲆（Scophthalmus maximus）的精子发生和激素水平

大菱鲆（Scophthalmus maximus）是欧洲和华北地区重要的海洋鱼类。尽管有大量关于大菱鲆繁殖的研究，但精子发生的完整细胞学过程仍不清楚。在这项研究中，我们研究了整个繁殖季节总共 23 种雄性生殖细胞的亚显微结构，初级精母细胞的过程相对完整。我们发现精子细胞尾部在精子细胞II早期形成，精子中至少有16个球形线粒体。肝体指数（HSI）和性腺指数（GSI）均在繁殖季节达到峰值。初步分析表明，成熟精子活力与精子畸形比例呈负相关。血清 3,5,3'-三碘甲状腺原氨酸 (T3)、5-羟色胺 (5-HT)、睾酮 (T)、17α,20β-Dihydroxy-4-pregnen-3-one (17α,20β-DHP) 和 17β-雌二醇 (E2) 均在成熟期升高，其中 T 含量的变化最为明显。而在睾丸中，11-酮睾酮 (11-KT) 的整体高水平更为显着。雄激素受体(AR) mRNA的表达和定位表明，AR在II期(15-70 g)高表达，成熟期[IV(2200 g)至V(2500 g)略有反弹] ]，其变化先于 T 和 11-KT 的变化。荧光原位杂交（FISH）分析显示AR主要分布于但不限于支持细胞。这项研究代表了大菱鲆生殖周期和精子发生的最完整概述，