孕激素暴露致食蚊鱼形态雄性化的生物学效应

Progesterone induces morphological masculinization in immature female mosquitofish( Gambusia affinis)

目的研究不同浓度孕酮(PRO)暴露对雌性食蚊鱼(Gambusia affinis)的形态雄性化生物学效应。方法将性未成熟的雌性食蚊鱼个体分别静水暴露于0.5、5、50和500 nmol/L不同浓度的PRO实验组中,并设置对照组和平行组。持续暴露42 d后观察与测定食蚊鱼的体长、体重、臀鳍第3鳍条和第14,15,16椎肋骨形态雄性化变化等指标,同时观察卵巢发育状况。结果食蚊鱼暴露42 d后,与对照组相比,50和500 nmol/L实验组食蚊鱼的体长(BL)有极显著减少(分别P<0.01);无论是低浓度组还是高浓度组,暴露实验后体重(BW)都有显著性或极显著下降(P<0.05或P<0.01);PRO暴露对食蚊鱼身体健康指数(CF)的影响,只有在5 nmol/L浓度时差异有显著性(P<0.05);500 nmol/L浓度处理后,第3臀鳍条分节数(FJ)、长度(FL)和最宽处宽度(FW)差异有显著性(P<0.05),表明形态雄性化变化明显;其他浓度组则无明显区别(P>0.05);500 nmol/L PRO实验组中,雌性食蚊鱼的第14,15,16椎肋骨的L值、D值和L!D值都出现极显著性差异(分别P<0.01),表明形态雄性化变化明显;组织切片观察揭示,暴露组食蚊鱼卵巢中的卵母细胞发育受到不同程度的抑制,II、III时相卵母细胞胞核发生肿胀现象。结论孕激素暴露诱导雌性食蚊鱼形态雄性化的生物效应十分明显。

Objective The aim of this study was to investigate the masculinizing effects of progesterone （ PRO） exposure at different concentrations on the morphology of female mosquitofish （Gambusia affinis）.Methods Immature female G.affinis individuals were put into static water with 0.5, 5, 50 and 500 nmol/L progesterone （n=56）, respective-ly.In addition, control group and parallel groups were set up .After 42-day-long exposure, we measured four main indexes of the G.affinis：the body length, body weight, morphological changes in the anal fin 3rd fin and the 14, 15 and 16 verte-bral ribs.We also observed the state of ovarian development .Results The body lengths （BL） of experimental groups ex-posed at concentration of 50 and 500 nmol/L progesterone for 42 d showed significant differences , respectively （ P＆lt;0.01 for both）, when compared with those of the control group .The body weights （BW） of experimental groups exposed to pro-gesterone at all concentrations were significantly or very significantly decreased （P＆lt;0.05 or P＆lt;0.01）.Only the proges-terone at 5 nmol/L concentration showed significant effect on the body health index （CF） （P＆lt;0.05）.The section number （FJ） of the anal fin 3rd fin, the section length （FL）and the widest portion width （FW）in the experimental groups had sig-nificant difference （P＆lt;0.05）, respectively, showing significant changes in morphology after the exposure to 500 nmol/L progesterone .However , there was no significant difference between the values resulted by progesterone in other concentra -tions （P＆gt;0.05）.When exposed to 500 nmol/L PRO, the L, D and L：D values of the 14th, 15th and 16th vertebral ribs of the female G.affinis had very significant difference （ P＆lt;0.01 for all ） , respectively , indicating significant changes of morphological masculinization .Histological examination revealed that the developmental status of the ovaries of G.affinis in the experimental groups were to different degrees inhibited , and the nuclei appeared swelling in stage II and III oocytes . Conclusions The results of this study indicate apparent masculinizing effects of progesterone on immature female mosquit -ofish.