Data from: The fate of W chromosomes in hybrids between wild silkmoths, Samia cynthia ssp.: no role in sex determination and reproduction

Moths and butterflies (Lepidoptera) have sex chromosome systems with female heterogamety (WZ/ZZ or derived variants). The maternally inherited W chromosome is known to determine female sex in the silkworm, Bombyx mori. However, little is known about the role of W chromosome in other lepidopteran species. Here we describe two forms of the W chromosome, W and neo-W, that are transmitted to both sexes in offspring of hybrids from reciprocal crosses between subspecies of wild silkmoths, Samia cynthia. We performed crosses between S. c. pryeri (2n=28, WZ/ZZ) and S. c. walkeri (2n=26, neo-Wneo-Z/neo-Zneo-Z) and examined fitness and sex chromosome constitution in their hybrids. The F1 hybrids of both reciprocal crosses had reduced fertility. Fluorescence in situ hybridization revealed not only the expected sex chromosome constitutions in the backcross and F2 hybrids of both sexes but also females without the W (or neo-W) chromosome and males carrying the W (or neo-W) chromosome. Furthermore, crosses between the F2 hybrids revealed no association between the presence or absence of W (or neo-W) chromosome and variations in the hatchability of their eggs. Our results clearly suggest that the W (or neo-W) chromosome of S. cynthia ssp. plays no role in sex determination and reproduction, and thus does not contribute to the formation of reproductive barriers between different subspecies.鳞翅目（Lepidoptera）蛾类与蝴蝶的性染色体系统为雌性异配型（WZ/ZZ或其衍生变体）。母系遗传的W染色体在家蚕（Bombyx mori）中已被证实可决定雌性性别。然而，学界对其他鳞翅目物种中W染色体的功能仍知之甚少。本研究报道了野生蓖麻蚕（Samia cynthia）不同亚种正反交杂种后代中存在两种W染色体形式——W染色体与新W染色体（neo-W），且二者可传递至杂种的雌雄个体中。我们以蓖麻蚕 pryeri 亚种（S. c. pryeri，2n=28，核型WZ/ZZ）与蓖麻蚕 walkeri 亚种（S. c. walkeri，2n=26，核型neo-Wneo-Z/neo-Zneo-Z）为亲本开展杂交实验，并对其杂种的适合度与性染色体组成进行了检测。两种正反交组合的F1杂种均表现出育性下降。荧光原位杂交（fluorescence in situ hybridization, FISH）结果显示，不仅在回交及F2代雌雄个体中检测到预期的性染色体组成，还发现了缺失W（或新W）染色体的雌性个体，以及携带W（或新W）染色体的雄性个体。进一步的F2代杂种间杂交实验表明，W（或新W）染色体的有无与虫卵孵化率的差异无显著关联。本研究结果明确证实：蓖麻蚕（Samia cynthia）亚种的W（或新W）染色体不参与性别决定与生殖调控过程，因此不会促成不同亚种间生殖隔离的形成。