Understanding the fundamental reproductive biology of a species is the first step toward identifying parameters that are critical for reproduction and for the development of assisted reproductive techniques. Ejaculates were collected from aquarium (n = 24) and in situ (n = 34) sand tiger sharks Carcharias taurus. Volume, pH, osmolarity, sperm concentration, motility, status, morphology, and plasma membrane integrity were assessed for each ejaculate. Semen with the highest proportion of motile sperm was collected between April and June for both in situ and aquarium sand tiger sharks indicating a seasonal reproductive cycle. Overall, 17 of 30 semen samples collected from aquarium sharks from April through June contained motile sperm compared to 29 of 29 of in situ sharks, demonstrating semen quality differences between aquarium and in situ sharks. Sperm motility, status, morphology, and plasma membrane integrity were significantly higher (P < 0.05) for in situ compared to aquarium sand tiger sharks. Testosterone was measured by an enzyme immunoassay validated for the species. Testosterone concentration was seasonal for both aquarium and in situ sharks with highest concentrations measured in spring and lowest in summer. In situ sharks had higher (P < 0.05) testosterone concentration in spring than aquarium sharks. This study demonstrated annual reproduction with spring seasonality for male sand tiger sharks through marked seasonal differences in testosterone and semen production. Lower testosterone and poorer semen quality was observed in aquarium sharks likely contributing to the species’ limited reproductive success in aquariums.

中文翻译：

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沙虎鲨 Carcharias taurus 的睾酮和精液季节性†

了解物种的基本生殖生物学是确定对繁殖和辅助生殖技术发展至关重要的参数的第一步。从水族馆 (n = 24) 和原位 (n = 34) 沙虎鲨 Carcharias taurus 收集射精。对每次射精的体积、pH、渗透压、精子浓度、运动性、状态、形态和质膜完整性进行评估。4 月至 6 月期间，原位沙虎鲨和水族馆沙虎鲨均采集了活动精子比例最高的精液，表明存在季节性生殖周期。总体而言，4 月至 6 月从水族馆鲨鱼收集的 30 份精液样本中有 17 份含有活动精子，而 29 份原位鲨鱼中的 29 份含有活动精子，这表明水族馆鲨鱼和原位鲨鱼之间的精液质量存在差异。与水族馆沙虎鲨相比，原位的精子活力、状态、形态和质膜完整性显着更高（P < 0.05）。通过针对该物种验证的酶免疫测定法测量睾酮。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。与水族馆沙虎鲨相比，原位的质膜完整性显着更高（P < 0.05）。通过针对该物种验证的酶免疫测定法测量睾酮。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。与水族馆沙虎鲨相比，原位的质膜完整性显着更高（P < 0.05）。通过针对该物种验证的酶免疫测定法测量睾酮。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。05) 原位与水族馆沙虎鲨相比。睾酮是通过对物种进行验证的酶免疫测定法来测量的。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。05) 原位与水族馆沙虎鲨相比。通过针对该物种验证的酶免疫测定法测量睾酮。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。水族馆和原位鲨鱼的睾酮浓度是季节性的，春季测得的浓度最高，夏季测得的最低。春季原位鲨鱼的睾酮浓度高于水族馆鲨鱼（P < 0.05）。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。这项研究通过睾酮和精液产生的显着季节性差异，证明了雄性沙虎鲨的春季季节性繁殖。在水族馆鲨鱼中观察到较低的睾丸激素和较差的精液质量，这可能导致该物种在水族馆中繁殖成功率有限。