Ito Lauro Satoru, Yamashita Michiaki, Strüssmann Carlos Augusto
Tokyo University of Fisheries, Department of Aquatic Biosciences, Konan 4-5-7, Minato-Ku, Tokyo 108-8477, Japan.
J Exp Zool A Comp Exp Biol. 2003 Jun 1;297(2):169-79.
Elevated temperature causes degeneration and disappearance of the germ cells in the males of scrotal mammals. It was recently shown that heat-induced germ cell degeneration occurs also in fish but, unlike in mammals, it occurs not only in males but also in females. The purpose of this study was to clarify the histological process and dynamics of heat-induced germ cell disappearance in pejerrey Odontesthes bonariensis larvae and juveniles. Monosex and mixed-sex fish produced by thermal manipulation of sex (temperature-dependent sex determination) were subjected to 29 degrees C for periods between 1 and 12 weeks, and used to analyze, by histological methods, the changes in gonadal size and the number of normal and degenerating germ cells. Groups exposed to 29 degrees C for 8-12 weeks were subsequently transferred to 24 degrees C to verify if any gonadal damage would be permanent. Germ cell degeneration, histologically characterized by nuclear pyknosis or eosinophilia and cytoplasmic eosinophilia, was observed with increasing frequency at higher temperatures (29>24> 17 degrees C) and more in males than in females. Clear degenerative changes in the germinal epithelium usually began within one week of exposure to 29 degrees C and appeared clearer in females than in males. Complete loss of germ cells was observed only in individuals exposed for periods of 8-12 weeks to 29 degrees C but no treatment produced 100% sterile fish. Germ cells that remained in the gonads after exposure to 29 degrees C retained the capacity to rapidly recolonize germ cell-depleted areas, suggesting that the associated somatic cells in the gonads are little or not affected by this temperature.
高温会导致阴囊哺乳动物雄性生殖细胞的退化和消失。最近研究表明，热诱导的生殖细胞退化在鱼类中也会发生，但与哺乳动物不同的是，它不仅发生在雄性中，也发生在雌性中。本研究的目的是阐明佩氏南美无须魮（Odontesthes bonariensis）幼体和成体中热诱导生殖细胞消失的组织学过程和动态变化。通过对性别的热调控（温度依赖性性别决定）产生的单性和混合性别的鱼类，在29摄氏度下处理1至12周，然后用组织学方法分析性腺大小的变化以及正常和退化生殖细胞的数量。将暴露于29摄氏度8至12周的组随后转移到24摄氏度，以验证是否有任何性腺损伤是永久性的。生殖细胞退化在组织学上表现为核固缩或嗜酸性以及细胞质嗜酸性，在较高温度（29>24>17摄氏度）下观察到其频率增加，且雄性比雌性更明显。生殖上皮的明显退行性变化通常在暴露于29摄氏度一周内开始，在雌性中比在雄性中更明显。仅在暴露于29摄氏度8至12周的个体中观察到生殖细胞完全消失，但没有任何处理产生100%不育的鱼。暴露于29摄氏度后留在性腺中的生殖细胞保留了迅速重新定殖生殖细胞耗尽区域的能力，这表明性腺中的相关体细胞很少或不受该温度影响。
