Xie Yuan-Yuan, Wang Ke-Yu, Yang Rui-Jia, Chen Hui-Xia, Liang Li
Hebei Collaborative Innovation Center for Eco-Environment; Hebei Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology; College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, Hebei Province, People's Republic of China.
Ministry of Education Key Laboratory of Molecular and Cellular Biology, Shijiazhuang, 050024, Hebei Province, People's Republic of China.
Parasit Vectors. 2025 Aug 3;18(1):328. doi: 10.1186/s13071-025-06972-z.
The family Rhadinorhynchidae is a common group of acanthocephalans parasitizing various marine and freshwater fishes. The current knowledge of the pattern of mitogenomic evolution of the rhadinorhynchid acanthocephalans is still extremely limited. The monophyly of the Rhadinorhynchidae and the phylogenetic status of several of its included genera and subfamilies remain under debate.
The complete mitogenomes of Micracanthorhynchina hemirhamphi and Rhadinorhynchus laterospinosus were sequenced and annotated for the first time on the basis of the specimens collected from the Asian pencil halfbeak Hyporhamphus intermedius (Cantor) (Beloniformes: Hemiramphidae) and the frigate tuna Auxis thazard (Lacepède) (Scombriformes: Scombridae), respectively. Phylogenetic analyses of Acanthocephala were performed on the basis of the concatenated amino acid sequences of 12 protein-coding genes (PCGs) of mitogenomes using maximum likelihood (ML) and Bayesian inference (BI), respectively.
The complete mitogenomes of M. hemirhamphi and R. laterospinosus are 17,272 bp and 13,567 bp in length, which both include 36 genes, containing 12 PCGs (missing atp8), 22 transfer RNA (tRNA) genes, and two ribosomal RNAs (rrnS and rrnL), plus two noncoding regions. Additionally, several tRNA gene rearrangement events occurred in the mitogenomes of both M. hemirhamphi and R. laterospinosus. Phylogenetic results supported the traditional rhadinorhynchid genus Micracanthorhynchina as a distinct lineage from Rhadinorhynchidae and Cavisomatidae.
The mitogenome of M. hemirhamphi represents the largest mitogenome of acanthocephalan reported so far. The mitogenome of R. laterospinosus is the smallest mitogenome of the order Echinorhynchida, which also represents the first mitogenomic data for the genus Rhadinorhynchus and also for the Rhadinorhynchidae sensu stricto. Comparative mitogenomic analyses revealed the gene arrangements of R. laterospinosus and M. hemirhamphi represent two new types of mitochondrial gene arrangement reported in Acanthocephala. Moreover, mitogenomic phylogenies further confirmed the validity of the family Micracanthorhynchinidae and suggested a sister relationship Micracanthorhynchinidae + (Rhadinorhynchidae + Cavisomatidae) within Echinorhynchida.
放射吻钩科是一类常见的棘头虫，寄生于各种海洋和淡水鱼类。目前关于放射吻钩科棘头虫线粒体基因组进化模式的了解仍然极为有限。放射吻钩科的单系性及其所含几个属和亚科的系统发育地位仍存在争议。
首次基于分别从亚洲铅笔鱼Hyporhamphus intermedius（坎托）（颌针鱼目：鱵科）和扁舵鲣Auxis thazard（拉塞佩德）（鲭形目：鲭科）采集的标本，对半吻小棘吻虫Micracanthorhynchina hemirhamphi和侧棘放射吻钩虫Rhadinorhynchus laterospinosus的完整线粒体基因组进行了测序和注释。基于线粒体基因组12个蛋白质编码基因（PCG）的串联氨基酸序列，分别使用最大似然法（ML）和贝叶斯推断法（BI）对棘头虫进行系统发育分析。
半吻小棘吻虫和侧棘放射吻钩虫的完整线粒体基因组长度分别为17,272 bp和13,567 bp，均包含36个基因，包括12个PCG（缺少atp8）、22个转运RNA（tRNA）基因和两个核糖体RNA（rrnS和rrnL），外加两个非编码区。此外，半吻小棘吻虫和侧棘放射吻钩虫的线粒体基因组中均发生了几处tRNA基因重排事件。系统发育结果支持传统的放射吻钩科属半吻小棘吻虫属作为一个与放射吻钩科和腔吻科不同的谱系。
半吻小棘吻虫的线粒体基因组是迄今为止报道的棘头虫中最大的线粒体基因组。侧棘放射吻钩虫的线粒体基因组是棘吻目最小的线粒体基因组，这也代表了放射吻钩虫属以及狭义放射吻钩科的首个线粒体基因组数据。比较线粒体基因组分析表明，侧棘放射吻钩虫和半吻小棘吻虫的基因排列代表了棘头虫中报道的两种新的线粒体基因排列类型。此外，线粒体基因组系统发育进一步证实了半吻小棘吻虫科的有效性，并表明在棘吻目中半吻小棘吻虫科 + （放射吻钩科 + 腔吻科）为姐妹关系。
