Alves M J, Coelho M M, Próspero M I, Collares-Pereira M J
Centro de Biologia Ambiental, Departamento de Zoologia e Antropologia, Faculdade de Ciências, Universidade de Lisboa, 1700 Lisboa, Portugal.
Genetics. 1999 Jan;151(1):277-83. doi: 10.1093/genetics/151.1.277.
The hybrid minnow Rutilus alburnoides comprises diploid and polyploid females and males. Previous studies revealed that diploid and triploid females exhibit altered oogenesis that does not involve random segregation and recombination of the genomes of the two ancestors, constituting unisexual lineages. In the present study, we investigated the reproductive mode of hybrid males from the Tejo basin, using experimental crosses and flow cytometric analysis of blood and sperm. The results suggest that diploid hybrids produced fertile unreduced sperm, transmitting their hybrid genome intact to offspring. Triploid hybrids also produced unreduced sperm, but it was not possible to obtain data concerning their fertility. Finally, tetraploid hybrids produced fertile diploid sperm, which exhibited Mendelian segregation. Tetraploid R. alburnoides may reestablish biparental reproduction, as individuals of both sexes with the appropriate constitution for normal meiosis (two haploid genomes from each parental species) are likely to occur in natural populations. Tetraploids probably have arisen from syngamy of diploid eggs and diploid sperm produced by diploid hybrid males. Diploid hybrid males may therefore play a significant role in the dynamics of the complex, starting the evolutionary process that may ultimately lead to a new sexually reproducing species.
杂种米诺鱼（Rutilus alburnoides）包括二倍体和多倍体的雌性和雄性个体。先前的研究表明，二倍体和三倍体雌性个体的卵子发生过程发生了改变，这一过程不涉及两个祖先基因组的随机分离和重组，从而形成了单性谱系。在本研究中，我们利用实验杂交以及对血液和精子的流式细胞术分析，研究了来自特茹河流域的杂种雄性个体的生殖模式。结果表明，二倍体杂种产生了可育的未减数精子，将其杂种基因组完整地传递给了后代。三倍体杂种也产生了未减数精子，但无法获得有关其育性的数据。最后，四倍体杂种产生了可育的二倍体精子，这些精子表现出孟德尔分离现象。四倍体R. alburnoides可能重新建立了双亲繁殖方式，因为在自然种群中可能会出现具有正常减数分裂合适组成的雌雄个体（每个亲本物种的两个单倍体基因组）。四倍体可能起源于二倍体杂种雄性产生的二倍体卵子和二倍体精子的受精作用。因此，二倍体杂种雄性可能在这个复杂体系的动态变化中发挥重要作用，启动可能最终导致一个新的有性繁殖物种出现的进化过程。
