INRA, UMR 1224 Ecobiop, Pôle d'Hydrobiologie, Quartier Ibarron, 64310, Saint Pée sur Nivelle, France.
Fish Physiol Biochem. 2013 Oct;39(5):1129-40. doi: 10.1007/s10695-013-9769-7. Epub 2013 Jan 19.
In European eel, it has been proposed that the undifferentiated gonad would develop into either an intersexual stage (Syrski organ) or directly into an ovary. The Syrski organ could then develop into either an ovary or a testis. In the present study, glass eels were raised until they reached a minimum size of 29 cm for histological sex assessment. In addition, some undifferentiated individuals with size encompassing 15-28 cm were sampled in a female-biased population (Oir River). We also investigated aromatase gene expression, which is known to be involved in the process of fish sex differentiation. Gonad histology revealed that intersexual eels were characterized by a small number of oocytes within a predominant testis-like structure. Males were significantly smaller than intersexual eels, which suggests that all males do not necessarily pass through an intermediate intersexual stage. Aromatase transcript levels in intersexual eels gonads and testes were similar but significantly lower than in ovaries and were comparable between ovaries and undifferentiated gonads from the females-biased population. In addition, condition factor was lower in female than in intersexual individuals. Together, these results provide evidence that ovaries would not develop from the Syrski organ.
在欧洲鳗鲡中，人们提出未分化的性腺将发育成中间性阶段（Syrski 器官）或直接发育成卵巢。然后，Syrski 器官可以发育成卵巢或睾丸。在本研究中，我们将玻璃鳗饲养到最小尺寸达到 29 厘米，以进行组织学性别评估。此外，在一个雌性偏向的 Oir 河种群中，我们还采集了一些大小在 15-28 厘米之间的未分化个体。我们还研究了芳香酶基因的表达，已知该基因参与鱼类性别分化过程。性腺组织学显示，中间性鳗鱼的特征是在主要的睾丸样结构内有少量的卵母细胞。雄性明显小于中间性鳗鱼，这表明并非所有雄性都必然经过中间性阶段。中间性鳗鱼性腺和睾丸中的芳香酶转录本水平相似，但明显低于卵巢，并且与雌性偏向种群中卵巢和未分化性腺之间的水平相当。此外，雌性的条件系数低于中间性个体。综上所述，这些结果表明卵巢不会从 Syrski 器官发育而来。
