Distant hybridization between the sea urchin Heliocidaris crassispina (♀) and the sea urchin Strongylocentrotus intermedius (♂) was successfully performed under laboratory conditions. A new variety of hybrid sea urchin (HS hybrid) was obtained. However, the early-development success rates for the HS hybrids were significantly lower than those of purebred H. crassispina or S. intermedius offspring. In addition, it was difficult to distinguish the HS-hybrid adults from the pure H. crassispina adults, which might lead to confusion in subsequent breeding attempts. In this study, we attempted to develop a method to quickly and effectively identify HS hybrids, and to preliminarily investigate the molecular mechanisms underlying the poor early-development success rates in the HS hybrids. The hybrid sea urchins (HS hybrids) were identified both morphologically and molecularly. There were no significant differences in the test height to test diameter ratios between the HS hybrids and the parents. The number and arrangement of ambulacral pore pairs in the HS hybrids differed from those of the parental lines, which might serve as a useful morphological character for the identification of the HS hybrids. A primer pair that identified the HS hybrids was screened by comparing the mitochondrial genomes of the parental lines. Moreover, paternal leakage induced mitochondrial DNA heteroplasmy in the HS hybrids, which might explain the low rates of early development success in these hybrids. The distant-hybrid sea urchins were accurately identified using comparative morphological and molecular genetic methods. The first evidence of mtDNA heteroplasmy after the distant hybridization of an echinoderm was also provided.

中文翻译：

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Heliocidaris crassispina（♀）和Strongylocentrotus intermedius（♂）的远缘杂种：鉴定和mtDNA异质性分析。

在实验室条件下，海胆Heliocidaris crassispina（♀）和海胆Strongylocentrotus intermedius（♂）之间进行了远距离杂交。获得了新的杂种海胆（HS hybrid）。但是，HS杂种的早期发育成功率明显低于纯种H. crassispina或inter。intermedius后代。此外，很难将HS杂种与纯种H. crassispina成虫区分开来，这可能导致随后的育种尝试混淆。在这项研究中，我们试图开发一种方法来快速有效地鉴定HS杂种，并初步研究HS杂种早期开发成功率低的分子机制。混合海胆（HS杂种）在形态和分子上都得到了鉴定。HS杂种与亲本之间的测试高度与测试直径之比没有显着差异。HS杂种中的眼球孔对的数量和排列与亲本系不同，这可能是鉴定HS杂种的有用形态特征。通过比较亲本系的线粒体基因组来筛选鉴定HS杂种的引物对。此外，父系泄漏导致HS杂种中的线粒体DNA异质性，这可能解释了这些杂种中早期开发成功率较低。使用比较形态学和分子遗传学方法可以准确地识别出远处的混合海胆。