Important aspects of vertebrate reproduction, such as gametogenesis, involve changes in organs found deep internally and thus not easily studied directly in most living vertebrates due to obscuring pigment and overlying tissues. Transparent lines of zebrafish, especially the Casper double mutant, allow direct observation and analysis of reproductive events in the gonads in vivo. The natural production of fertilized eggs in zebrafish is a complex process involving oogenesis, spermatogenesis, mating behavior, endocrine and neurological processes with inputs from the environment including light, temperature and nutrition. While these factors play important roles, the hypothalamic-pituitary-gonadal axis (HPGA) is central in the regulation of embryo output. Endocrine disrupting compounds (EDCs) include a variety of pollutants often present in the environment. EDCs may have direct effects on the HPGA or indirect effects through toxic action on supporting organs such as the liver or kidney. Estrogenic compounds such as diethylstilbestrol (DES) have been reported to affect reproduction in a variety of species including man. In this study, the effects of DES on reproduction were determined in a novel way by using transparent Casper zebrafish that allow direct visualization of gonad status over time. Changes in gonad status with DES treatment were correlated with effects on secondary sex characteristics (i.e., genital vent size and breeding tubercles) spawning and embryo production. The results suggest that the Casper zebrafish is a useful model for studying dynamics of reproductive events in vertebrate gonads in vivo and for determining effects of EDCs on zebrafish reproduction.

中文翻译：

---

透明 Casper 斑马鱼的性腺状态、第二性征和产卵的体内评估

脊椎动物繁殖的重要方面，例如配子发生，涉及内部深层器官的变化，因此由于色素和上覆组织的模糊，在大多数活脊椎动物中不容易直接研究。斑马鱼的透明线，尤其是 Casper 双突变体，可以直接观察和分析体内性腺的生殖事件。斑马鱼受精卵的自然产生是一个复杂的过程，涉及卵子发生、精子发生、交配行为、内分泌和神经过程，环境输入包括光、温度和营养。虽然这些因素起着重要作用，但下丘脑-垂体-性腺轴 (HPGA) 是胚胎输出调节的核心。内分泌干​​扰物 (EDC) 包括环境中经常存在的各种污染物。EDC 可能对 HPGA 产生直接影响，也可能通过对支持器官（如肝脏或肾脏）的​​毒性作用产生间接影响。据报道，雌激素化合物如己烯雌酚 (DES) 会影响包括人类在内的多种物种的生殖。在这项研究中，DES 对繁殖的影响是通过使用透明的 Casper 斑马鱼以一种新颖的方式确定的，这种斑马鱼允许随着时间的推移直接观察性腺状态。DES 治疗的性腺状态变化与对第二性征（即生殖口大小和繁殖结节）产卵和胚胎生产的影响相关。