Chu-Koo F, Dugué R, Alván Aguilar M, Casanova Daza A, Alcántara Bocanegra F, Chávez Veintemilla C, Duponchelle F, Renno J-F, Tello Salvador, Nuñez J
IIAP, PEA, Iquitos, Peru.
Fish Physiol Biochem. 2009 Mar;35(1):125-36. doi: 10.1007/s10695-008-9211-8. Epub 2008 Apr 23.
Arapaima gigas is an air-breathing giant fish of Amazonian rivers. Given its great economic and cultural importance, the aquaculture development of this species represents an evident solution to face the decline of wild populations. In captivity, reproduction occurs generally in large earthen ponds where stocks of a few tens of brooders are maintained together at the beginning of the rainy season (December-March in the Peruvian Amazon). Fry production relies on the spontaneous formation of male and female pairs, which build a nest, delimit a territory and guard the offspring for at least 20 days from other congeners and predators. However, as sex determination of A. gigas is not possible by morphological criteria, it is very difficult to optimize reproduction conditions and fry production in each pond, which seriously hampers the culture of this species. This situation prompted us to develop sexing methodologies based on (1) the detection of female specific plasma Vitellogenin (Vtg) using an enzyme immuno assay (EIA), and (2) the determination of plasma 17beta-estradiol and 11-ketotestosterone levels for immature specimens. The Vtg purification was performed by electro-elution after polyacrilamide gel electrophoresis (PAGE) from plasma of 17beta-estradiol treated A. gigas juveniles. Two different Vtg molecules were isolated, (Vtg(1) and Vtg(2)) with 184 and 112 kDa apparent molecular masses, respectively, and two antibodies were raised in rabbits for each Vtg molecule. Adult fish were 100% accurately sexed by Vtg EIA, while 100% of immature fish and 95% of adults were accurately sexed by 17beta-Estradiol and 11-Ketestosterone ratios. We also observed different color pattern development in male and female adult fish (6-year-olds) around the reproductive period.
巨骨舌鱼是亚马逊河流域一种可呼吸空气的大型鱼类。鉴于其巨大的经济和文化重要性，该物种的水产养殖发展是应对野生种群数量下降的一个明显解决方案。在圈养环境中，繁殖通常发生在大型土池中，在雨季开始时（秘鲁亚马逊地区为12月至3月），几十尾亲鱼被饲养在一起。鱼苗生产依赖于雌雄配对的自然形成，它们会筑巢、划定领地并保护后代至少20天，防止其他同类和捕食者的侵害。然而，由于无法通过形态学标准确定巨骨舌鱼的性别，因此很难优化每个池塘的繁殖条件和鱼苗产量，这严重阻碍了该物种的养殖。这种情况促使我们开发基于以下方法的性别鉴定方法：（1）使用酶免疫分析（EIA）检测雌性特异性血浆卵黄蛋白原（Vtg）；（2）测定未成熟标本的血浆17β-雌二醇和11-酮睾酮水平。通过聚丙烯酰胺凝胶电泳（PAGE）从经17β-雌二醇处理的巨骨舌鱼幼鱼血浆中进行电洗脱来纯化Vtg。分离出两种不同的Vtg分子（Vtg(1)和Vtg(2)），表观分子量分别为184 kDa和112 kDa，并针对每个Vtg分子在兔子体内制备了两种抗体。通过Vtg EIA对成年鱼进行性别鉴定的准确率为100%；而通过17β-雌二醇和11-酮睾酮比率对100%的未成熟鱼和95%的成年鱼进行性别鉴定的准确率也很高。我们还观察到成年雌雄鱼（6岁）在繁殖期前后有不同的颜色模式发育。
