Pavlidis Michael, Greenwood Lorraine, Scott Alexander P
Department of Biology, University of Crete, PO Box 2208, GR-71409, Heraklion, Crete, Greece.
Gen Comp Endocrinol. 2004 Sep 15;138(3):255-62. doi: 10.1016/j.ygcen.2004.06.004.
This paper reports the results of an experiment to determine whether sex ratio has any effect on the spawning efficiency of common dentex, Dentex dentex, broodstock. The paper also reports preliminary data on diurnal changes in water concentrations of steroids (measured on two separate occasions) in the same groups of fish. These latter observations were made to determine whether, using a non-invasive procedure, it was possible to relate hormonal changes in the fish to the "success of spawning." Mature fish were placed in broodstock tanks at three different sex ratios (Group A, 4 female:1 male; Group B, 1 female:1 male; and Group C, 1 female:4 male) and regularly monitored for egg production. At 18 days after the start of spawning, water samples were removed from all three tanks at 130 min intervals over a period of 24 h. At the end of spawning, water samples were removed at 4 h intervals. Free and conjugated steroids were extracted from the water and measured by radioimmunoassay. The highest number of eggs released, percentage of viable eggs, number of spawnings, spawning index, and relative fecundity were observed in Group B (1 female:1 male). The sex steroids testosterone (T), 11-ketotestosterone (11-KT), 17,20beta-P, and 17,20beta, 21-trihydroxy-pregn-4-en-3-one could be readily detected in water from all tanks. Concentrations of the conjugated forms (sulphate and glucuronide) were higher than those of the free form--with the exception of sulphated T and 11-KT. The concentrations of glucuronidated 17,20beta-P, sulphated 17,20beta-P, and free T appeared to be associated with the number of females in the tank and glucuronidated 11-KT concentrations with the number of males. In the first set of water samples (taken during the spawning period) there was also evidence for a cycle in steroid release with an acrophase during the afternoon and early evening, a few hours before the actual act of spawning. We were not able to show any association between steroid concentrations and success of spawning. However, since the data were derived from a "snapshot" of just a single day in what was a prolonged spawning period, this was perhaps not surprising. The results from the present study will help us to design experiments that are more able to answer this question.
本文报告了一项实验的结果，该实验旨在确定性别比例是否对普通真鲷（Dentex dentex）亲鱼的产卵效率有任何影响。本文还报告了同一组鱼类中类固醇水浓度的日变化（在两个不同时间测量）的初步数据。进行这些后期观察是为了确定，通过一种非侵入性程序，是否有可能将鱼体内的激素变化与“产卵成功率”联系起来。将成熟的鱼以三种不同的性别比例放入亲鱼缸中（A组，4雌：1雄；B组，1雌：1雄；C组，1雌：4雄），并定期监测产卵情况。在产卵开始后的第18天，在24小时内每隔130分钟从所有三个鱼缸中采集水样。在产卵结束时，每隔4小时采集水样。从水中提取游离和结合类固醇，并通过放射免疫测定法进行测量。在B组（1雌：1雄）中观察到释放的卵数量最多、存活卵的百分比、产卵次数、产卵指数和相对繁殖力最高。在所有鱼缸的水中都能很容易地检测到性类固醇睾酮（T）、11-酮睾酮（11-KT）、17,20β-双羟孕酮（17,20β-P）和17,20β,21-三羟基孕-4-烯-3-酮。结合形式（硫酸盐和葡糖醛酸酯）的浓度高于游离形式——硫酸化T和11-KT除外。葡糖醛酸化17,20β-P、硫酸化17,20β-P和游离T的浓度似乎与鱼缸中的雌鱼数量有关，而葡糖醛酸化11-KT的浓度与雄鱼数量有关。在第一组水样（在产卵期采集）中，也有证据表明类固醇释放存在一个周期，高峰期在下午和傍晚，即在实际产卵行为前几个小时。我们未能显示类固醇浓度与产卵成功率之间的任何关联。然而，由于这些数据仅来自于长时间产卵期内一天的“快照”，这也许并不奇怪。本研究的结果将有助于我们设计更能回答这个问题的实验。
