School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece.
School of Health Sciences, Department of Nursing, International Hellenic University, Thessaloniki, Greece.
Theriogenology. 2020 Apr 1;146:31-38. doi: 10.1016/j.theriogenology.2020.01.050. Epub 2020 Jan 27.
The recruitment of primary growth (PG) oocytes to the secondary growth (SG) phase within the ovulatory cycle, i.e. time interval between two sequential ovulation/spawning events, has rarely been examined in detail in a quantitative manner for batch spawning fishes with indeterminate fecundity. In the present study we analyzed the ovarian dynamics of Macedonian shad, Alosa macedonica, an iteroparous batch spawning clupeid with indeterminate fecundity, with the main goal to define the timing of PG recruitment and relate it to the ovulatory cycle. The latter was classified into four different phases (pre-ovulatory, running, post-ovulatory, intermediate) through postovulatory follicles and presence/absence of hydrated oocytes. Various indices of ovarian dynamics, including the formation and mean diameter of the advanced oocyte batch, the ovarian developmental stage, the oocyte size modality and the gonadosomatic index, varied among the ovulatory phases, evidencing cyclicity. Relative fecundity of newly recruited SG oocytes was used as an index of PG recruitment intensity and was shown to follow a specific pattern within the ovulatory cycle; PG recruitment occurred in a stepwise manner and in parallel with ovulation of the advanced oocyte batch, and synchronization of these two processes kept the ovary in a state of dynamic equilibrium.
在具有不定数量产卵的分批产卵鱼类中，很少有研究以定量的方式详细研究初级生长（PG）卵母细胞在排卵周期内（即两次连续排卵/产卵事件之间的时间间隔）向次级生长（SG）阶段的募集情况。在本研究中，我们分析了马其顿鲱（Alosa macedonica）的卵巢动态，马其顿鲱是一种具有不定数量产卵的多次产卵分批产卵的鲱鱼。主要目标是定义 PG 募集的时间，并将其与排卵周期相关联。后者通过排卵后卵泡和水合卵母细胞的存在/不存在分为四个不同阶段（排卵前、排卵中、排卵后、中间）。各种卵巢动态指数，包括成熟卵母细胞批的形成和平均直径、卵巢发育阶段、卵母细胞大小模式和性腺指数，在排卵阶段之间有所不同，表现出周期性。新募集的 SG 卵母细胞的相对丰度被用作 PG 募集强度的指标，并在排卵周期内呈现出特定的模式；PG 募集呈逐步进行，并与成熟卵母细胞批的排卵同时进行，这两个过程的同步使卵巢保持动态平衡状态。
