Cuellar O
Chromosoma. 1976 Nov 29;58(4):355-64. doi: 10.1007/BF00292843.
Female meiosis was analyzed in the triploid gynogenetic salamander Ambystoma tremblayi to determine the mechanism by which a stable chromosome number is maintained in this unisexual species. Gross details of the reproductive cycle and the cytology of meiosis were analyzed in 20 specimens and 320 oocytes involving all stages from early diplotene to the beginning of anaphase II. Ovulation apparently continues progressively involving a few oocytes at a time. Oocytes form the ovary contained chromosomes in diplotene, and diakinesis. The first metaphase was not observed since this stage occurs swiftly either immediately prior to or during ovulation. Oocytes in the most anterior region of the oviduct were in metaphase II, and those in the most posterior region were undergoing the beginning of anaphase II. Telophase II was not observed. Chromosome numbers obtained at all stages of prophase gave counts of approximately 42 bivalents, equivalent to the triploid somatic number known for this species. Similar numbers of dyads were obtained from metaphase II plates. This analysis supports earlier evidence suggesting that the triploid number of chromosomes in oocytes of A. tremblayi is doubled prior to meiosis, and the somatic number is restored by two normal meiotic divisions.
对三倍体雌核发育的蝾螈（Ambystoma tremblayi）的雌性减数分裂进行了分析，以确定在这个单性物种中维持稳定染色体数目的机制。对20个标本和320个卵母细胞（涵盖从双线期早期到后期II开始的所有阶段）的生殖周期总体细节和减数分裂细胞学进行了分析。排卵显然是逐步进行的，一次涉及少数卵母细胞。卵巢中的卵母细胞在双线期和终变期含有染色体。未观察到第一次中期，因为这个阶段在排卵前或排卵期间迅速发生。输卵管最前端区域的卵母细胞处于中期II，最后端区域的卵母细胞正处于后期II开始阶段。未观察到末期II。在前期各阶段获得的染色体数计数约为42个二价体，相当于该物种已知的三倍体体细胞数。从中期II平板获得的二分体数量相似。该分析支持了早期证据，表明A. tremblayi卵母细胞中的三倍体染色体数在减数分裂前加倍，并且通过两次正常的减数分裂恢复体细胞数。
