Asem Alireza, Yang Chaojie, De Vos Stephanie, Mahmoudi Farnaz, Xia Lidong, Shen Chun-Yang, Hontoria Francisco, Rogers D Christopher, Gajardo Gonzalo
College of Fisheries and Life Sciences, Hainan Tropical Ocean University, Sanya, 572000, China.
Department of Applied Animal Science and Welfare, Swedish University of Agricultural Sciences, Aquakultur, Sweden.
BMC Genomics. 2025 Mar 10;26(1):228. doi: 10.1186/s12864-025-11391-6.
The brine shrimp Artemia, a crustacean adapted to the extreme conditions of hypersaline environments, comprises nine regionally distributed sexual species scattered (island-like) over heterogeneous environments and asexual (parthenogenetic) lineages with different ploidies. Such sexual and asexual interaction within the genus raises questions regarding the origin and time of divergence of both sexual species and asexual lineages, including the persistence of the latter over time, a problem not yet clarified using single mitochondrial and nuclear markers. Based on the complete mitochondrial genome of all species and parthenogenetic lineages, this article first describes the mitogenomic characteristics (nucleotide compositions, genome mapping, codon usage, and tRNA secondary structure) of sexual species and asexual types and, secondly, it provides a comprehensive updated phylogenetic analysis. Molecular dating and geographical evidence suggest that the ancestral Artemia taxon originated in ca. 33.97 Mya during the Paleogene Period. The mitogenomic comparisons suggest that the common ancestor of diploid and triploid parthenogenetic lineages (ca. 0.07 Mya) originated from a historical ancestor (ca. 0.61 Mya) in the Late Pleistocene. Additionally, the common ancestor of tetraploid and pentaploid parthenogenetic lineages (ca. 0.05 Mya) diverged from a historical maternal ancestor with A. sinica (ca. 0.96 Mya) in the early Pleistocene. The parthenogenetic lineages do not share a direct ancestor with any sexual species. The Asian clade ancestor diverged more recently (ca. 14.27 Mya, Middle Miocene). The mitogenomic characteristics, maternal phylogenetic tree, and especially divergence time prove that A. monica and A. franciscana are two biological species.
卤虫（Artemia）是一种适应高盐极端环境的甲壳类动物，它包括九个区域分布的有性物种，这些物种分散（如岛屿般）在异质环境中，以及具有不同倍性的无性（孤雌生殖）谱系。该属内这种有性和无性的相互作用引发了关于有性物种和无性谱系的起源及分化时间的问题，包括后者随时间的持续存在，而使用单一的线粒体和核标记尚未阐明这一问题。基于所有物种和孤雌生殖谱系的完整线粒体基因组，本文首先描述了有性物种和无性类型的线粒体基因组特征（核苷酸组成、基因组图谱、密码子使用和tRNA二级结构），其次，提供了全面更新的系统发育分析。分子年代测定和地理证据表明，卤虫的祖先类群起源于古近纪约3397万年前。线粒体基因组比较表明，二倍体和三倍体孤雌生殖谱系的共同祖先（约7万年前）起源于晚更新世的一个历史祖先（约61万年前）。此外，四倍体和五倍体孤雌生殖谱系的共同祖先（约5万年前）在早更新世与中华卤虫（A. sinica）的一个历史母系祖先分化。孤雌生殖谱系与任何有性物种都没有直接的祖先关系。亚洲分支祖先的分化时间更近（约1427万年前，中新世中期）。线粒体基因组特征、母系系统发育树，尤其是分化时间证明，蒙氏卤虫（A. monica）和旧金山卤虫（A. franciscana）是两个生物学物种。
