Graziano Marco, Benito Raul, Planas Josep V, Palstra Arjan P
Department of Physiology and Immunology, School of Biology, University of Barcelona, Diagonal 643, 08028, Barcelona, Spain.
Wageningen Marine Research, Wageningen University & Research, Korringaweg 5, 4401, NT, Yerseke, The Netherlands.
BMC Dev Biol. 2018 Apr 12;18(1):10. doi: 10.1186/s12861-018-0170-8.
Male European seabass, already predominant (~ 70%) in cultured stocks, show a high incidence (20-30%) of precocious sexual maturation under current aquaculture practices, leading to important economic losses for the industry. In view of the known modulation of reproductive development by swimming exercise in other teleost species, we aimed at investigating the effects of sustained swimming on reproductive development in seabass males during the first year of life in order to determine if swimming could potentially reduce precocious sexual maturation.
Pre-pubertal seabass (3.91 ± 0.22 g of body weight (BW)) were subjected to a 10 week swimming regime at their optimal swimming speed (U) in an oval-shaped Brett-type flume or kept at rest during this period. Using Blazka-type swim tunnels, U was determined three times during the course of the experiment: 0.66 m s at 19 ± 1 g BW, 10.2 ± 0.2 cm of standard length (SL) (week 1); 0.69 m s at 38 ± 3 g BW, 12.7 ± 0.3 cm SL (week 5), and also 0.69 m s at 77 ± 7 g BW, 15.7 ± 0.5 cm SL (week 9). Every 2 weeks, size and gonadal weight were monitored in the exercised (N = 15) and non-exercised fish (N = 15). After 10 weeks, exercised and non-exercised males were sampled to determine plasma 11-ketotestosterone levels, testicular mRNA expression levels of genes involved in steroidogenesis and gametogenesis by qPCR, as well as the relative abundance of germ cells representing the different spermatogenic stages by histological examination.
Our results indicate that sustained swimming exercise at U delays testicular development in male European seabass as evidenced by decreased gonado-somatic index, slower progression of testicular development and by reduced mRNA expression levels of follicle stimulating hormone receptor (fshR), 3-beta-hydroxysteroid dehydrogenase (3βhsd), 11-beta hydroxysteroid dehydrogenase (11βhsd), estrogen receptor-beta (erβ2), anti-mullerian hormone (amh), structural maintenance of chromosomes protein 1B (smc1β), inhibin beta A (inhba) and gonado-somal derived factor 1 (gsdf1) in exercised males as compared with the non-exercised males.
Swimming exercise may represent a natural and non-invasive tool to reduce the incidence of sexually precocious males in seabass aquaculture.
在养殖种群中已占主导地位（约70%）的雄性欧洲海鲈，在当前水产养殖实践下性早熟发生率很高（20 - 30%），给该行业带来了重大经济损失。鉴于已知在其他硬骨鱼物种中游泳运动对生殖发育有调节作用，我们旨在研究持续游泳对海鲈雄性幼鱼第一年生殖发育的影响，以确定游泳是否有可能降低性早熟发生率。
将青春期前的海鲈（体重3.91 ± 0.22克）在椭圆形布雷特式水槽中以最佳游泳速度（U）进行为期10周的游泳训练，或在此期间保持静止。使用布拉兹卡式游泳隧道，在实验过程中三次测定U：体重19 ± 1克、标准体长10.2 ± 0.2厘米时为0.66米/秒（第1周）；体重38 ± 3克、标准体长12.7 ± 0.3厘米时为0.69米/秒（第5周）；体重77 ± 7克、标准体长15.7 ± 0.5厘米时也为0.69米/秒（第9周）。每2周监测一次运动组（N = 15）和非运动组（N = 15）鱼的大小和性腺重量。10周后，对运动组和非运动组雄性进行采样，通过qPCR测定血浆11 - 酮睾酮水平、参与类固醇生成和配子发生的基因的睾丸mRNA表达水平，以及通过组织学检查确定代表不同生精阶段的生殖细胞的相对丰度。
我们的结果表明，以U进行持续游泳训练会延迟雄性欧洲海鲈的睾丸发育，这表现为性腺 - 体指数降低、睾丸发育进程减慢，以及与非运动组雄性相比，运动组雄性中促卵泡激素受体（fshR）、3 - β - 羟基类固醇脱氢酶（3βhsd）、11 - β - 羟基类固醇脱氢酶（11βhsd）、雌激素受体 - β（erβ2）、抗苗勒管激素（amh）、染色体结构维持蛋白1B（smc1β）、抑制素βA（inhba）和性腺衍生因子1（gsdf1）的mRNA表达水平降低。
游泳训练可能是一种天然且非侵入性的工具，可降低海鲈养殖中性早熟雄性的发生率。
