A growing number of recent genomic studies report asexual parthenogenetic reproduction in a wide range of taxa, including vertebrate species from the reptile, bird, and fish lineages. Yet, self-fertilization (selfing) has been recorded only in a single vertebrate, the mangrove killifish Kryptolebias marmoratus. In cichlid fishes, sex determination is notably diverse and can be influenced by the environment, and sequential hermaphroditism has been reported for some species. Here, we present evidence for a case of facultative selfing in the cichlid fish Benitochromis nigrodorsalis, which is otherwise known as biparentally reproducing ovophilic mouthbrooder from Western Africa. Our laboratory observations revealed that a wild-caught individual produced repeatedly viable offspring in absence of a mating partner. By analyzing genome-wide single-nucleotide polymorphism (SNP) data, we compare that individual and two of its offspring to shed light on its reproductive mode. First, our results confirm uniparental reproduction. Second, overall heterozygosity is reduced in the offspring compared with outbred individuals. Retained maternal heterozygosity in the offspring is ∼51%, which is close to the theoretically expected value of a heterozygosity reduction of 50% by selfing. Heterozygosity patterns along individual chromosomes do not point to alternative parthenogenetic reproductive mechanisms like automixis by terminal or central fusion. Facultative selfing may represent an adaptive strategy ensuring reproduction when mating partners are absent and, hence, contribute to the cichlids’ enormous evolutionary success.

中文翻译：

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来自全基因组测序的脊椎动物自交证据

最近越来越多的基因组研究报告了多种类群中的无性孤雌生殖，包括爬行动物、鸟类和鱼类谱系的脊椎动物物种。然而，仅在一种脊椎动物——红树林鳉鱼Kryptolebias marmoratus中记录到了自体受精（自交） 。在丽鱼科鱼类中，性别决定明显多样化，并且可能受到环境的影响，并且已经报道了某些物种的连续雌雄同体。在这里，我们提供了丽鱼科鱼Benitochromis nigrodorsalis兼性自交案例的证据，这种鱼也被称为来自西非的双亲繁殖的亲卵口育鱼。我们的实验室观察表明，野生捕获的个体在没有交配伙伴的情况下可以反复产生可存活的后代。通过分析全基因组单核苷酸多态性 (SNP) 数据，我们比较该个体及其两个后代，以揭示其生殖模式。首先，我们的结果证实了单亲繁殖。其次，与远交个体相比，后代的总体杂合性降低。后代中保留的母本杂合度约为 51%，这接近自交杂合度降低 50% 的理论预期值。沿个体染色体的杂合性模式并不表明替代的孤雌生殖机制，例如通过末端或中心融合的自混合。兼性自交可能代表了一种适应性策略，确保在没有交配伙伴时进行繁殖，从而有助于丽鱼科鱼取得巨大的进化成功。