Graduate Program on the Cell and Structural Biology, Institute of Biology, University of Campinas-UNICAMP, Campinas, São Paulo, Brazil.
Theriogenology. 2013 Mar 1;79(4):709-24. doi: 10.1016/j.theriogenology.2012.11.028. Epub 2013 Jan 11.
The objective was to characterize female germ cell renewal during the annual reproductive cycle in two species of ostariophysian fish with distinct reproductive strategies: a siluriform, Pimelodus maculatus, in which oocyte development is group synchronous and the annual reproductive period is short; and a characiform, Serrasalmus maculatus, with asynchronous oocyte development and a prolonged reproductive period. These reproductive strategies result in fish determinate and indeterminate fecundity, respectively. Annual reproductive phases were determined by biometric and histologic analysis of gonads and interpreted according to new proposals for phase classification and stages of oocyte development (with special attention to germinal epithelium activity). Histologically, there were two types of oogonia in the germinal epithelium: single oogonia and those in mitotic proliferation. Oogonial proliferation and their entry into meiosis resulted in formation of cell nests (clusters of cells in the ovarian lamellae). Morphometric analysis was used to estimate germ cell renewal. Based on numbers of single oogonia in the lamellar epithelium, and nests with proliferating oogonia or early prophase oocytes throughout the annual reproductive cycle, oogonial proliferation and entrance into meiosis were more intense during the regenerating phase and developing phase, but decreased sharply (P < 0.05) during the spawning-capable phase. Oogonial proliferation gradually recovered during the regressing phase. We concluded that, independent of species or features of the reproductive cycle, germ cell renewal occurred during the regenerating phase, ensuring availability of eggs for the spawning event.
本研究旨在描述两种具有不同繁殖策略的骨鳔鱼目鱼类的雌性生殖细胞更新过程，这两种鱼类分别是：Siluriformes 目，Pimelodus maculatus，其卵母细胞发育具有群体同步性且每年的繁殖期较短；Characiformes 目，Serrasalmus maculatus，其卵母细胞发育具有异步性且繁殖期较长。这些繁殖策略导致了鱼类具有有定数和不定数的生殖能力。通过对性腺的生物测量和组织学分析来确定年度繁殖阶段，并根据卵母细胞发育阶段（特别关注生殖上皮细胞的活性）的新分类建议进行解释。组织学上，生殖上皮中有两种类型的卵原细胞：单卵原细胞和有丝分裂增殖的卵原细胞。卵原细胞的增殖及其进入减数分裂导致细胞巢的形成（卵巢板层中的细胞簇）。形态计量学分析用于估计生殖细胞更新。基于板层上皮中单卵原细胞的数量以及含有增殖卵原细胞或早期前期卵母细胞的巢的数量，在整个年度繁殖周期中，卵原细胞的增殖和进入减数分裂在再生期和发育期更为活跃，但在可产卵期急剧下降（P<0.05）。卵原细胞增殖在退化期逐渐恢复。我们得出结论，无论物种或繁殖周期的特征如何，生殖细胞更新都发生在再生期，这确保了卵子在产卵事件中的可用性。
