Senckenberg am Meer, German Centre for Marine Biodiversity Research, Südstrand 44, 26382, Wilhelmshaven, Germany.
BMC Evol Biol. 2020 Mar 14;20(1):36. doi: 10.1186/s12862-020-1594-x.
The family Aegisthidae is known as typical component of deep-sea hyperbenthic waters that gradually colonized other marine environments. The phylogenetic relationships within this family have been examined here including hyperbenthic, planktonic, benthic forms and two associated Aegisthidae species.
Ninety four specimens belong to 14 genera were studied using 18S and 28S rRNA and COI mtDNA. Bayesian analysis supports the monophyly of 10 genera whereas Andromastax, Jamstecia, Nudivorax and Aegisthus revealed to be paraphyletic. The first offshoot of the phylogenetic tree is a clade consists of the undescribed genus Aegisthidae gen.1 sister to the two monophyletic genera Cerviniella and Hase, whereas the other Cerviniinae members (represented by Cervinia and Expansicervinia) assemble a monophylum, sister to the hyperbenthic and planktonic aegisthid genera, resulting in the paraphyly of the subfamily Cerviniinae. Hence, we defined the new subfamily Cerviniellinae subfam. nov. encompassing the three benthic genera Cerviniella, Hase and Eucanuella. The subfamily Cerviniinae has been re-defined to include Cervinia, Expansicervinia and Paracerviniella. Members of the subfamily Pontostratiotinae were clustered into two clades, one consists of the genus Stratiopontotes sister to an undescribed genus + Cerviniopsis and Siphonis. The second contains Pontostratiotes sister to the members of the planktonic subfamily Aegisthinae, resulting in the paraphyly of the Pontostratiotinae. Therefore, the Pontostratiotinae has been re-defined to include only members of the genus Pontostratiotes; whereas the subfamily Cerviniopseinae has been re-erected and re-defined containing Stratiopontotes, Cerviniopsis, Siphonis, Aegisthidae gen. 2, Herdmaniopsis, Hemicervinia and Tonpostratiotes. Within this subfamily, the associated Siphonis clusters as sister to the Cerviniopsis represents an example of convergent evolution in which the possession of a stylet-like mandible and an oral cone reminiscent of the Siphonostomatoida. The planktonic Aegisthus, Andromastax, Jamstecia, Nudivorax and Scabrantenna confirm the monophylom Aegisthinae, sister to the Pontostratiotinae.
Our DNA based phylogeny reveals the deep-sea origin of Aegisthidae by placing benthic Aegisthidae gen.1 and Cerviniellinae subfam. nov. as the most basal lineages. Secondary adaptations to hyperbenthic and planktonic realms, as well as associated lifestyle were discovered here by the derived positions of Pontostratiotinae, Aegisthinae and Siphonis respectively.
Aegisthidae 科被认为是深海海底生物的典型组成部分，它们逐渐占领了其他海洋环境。本研究对该科内的系统发育关系进行了研究，包括深海海底生物、浮游生物、底栖生物和两种相关的 Aegisthidae 物种。
使用 18S 和 28S rRNA 和 COI mtDNA 研究了 94 个属于 14 个属的标本。贝叶斯分析支持 10 个属的单系性，而 Andromastax、Jamstecia、Nudivorax 和 Aegisthus 被证明是并系的。系统发育树的第一个分支是一个由未命名的 Aegisthidae gen.1 属组成的分支，与两个单系属 Cerviniella 和 Hase 姐妹关系，而其他 Cerviniinae 成员（以 Cervinia 和 Expansicervinia 为代表）则形成一个单系群，与深海和浮游的 aegisthid 属姐妹关系，导致 Cerviniinae 亚科的并系性。因此，我们定义了新的 Cerviniellinae 亚科 nov.，包括 Cerviniella、Hase 和 Eucanuella 三个底栖属。Cerviniinae 亚科被重新定义为包括 Cervinia、Expansicervinia 和 Paracerviniella。Pontostratiotinae 亚科的成员聚类为两个分支，一个分支由 Stratiopontotes 属与一个未命名的属+Cerviniopsis 和 Siphonis 组成姐妹关系。第二个分支包含 Pontostratiotes，与浮游亚科 Aegisthinae 的成员姐妹关系，导致 Pontostratiotinae 的并系性。因此，Pontostratiotinae 被重新定义为仅包括 Pontostratiotes 属的成员；而 Cerviniopseinae 亚科被重新建立并重新定义，包括 Stratiopontotes、Cerviniopsis、Siphonis、Aegisthidae gen.2、Herdmaniopsis、Hemicervinia 和 Tonpostratiotes。在这个亚科中，相关的 Siphonis 聚类为 Cerviniopsis 的姐妹关系，这是趋同进化的一个例子，其中具有类似于 Siphonostomatoida 的颚状下颚和口腔锥体。浮游的 Aegisthus、Andromastax、Jamstecia、Nudivorax 和 Scabrantenna 证实了 Aegisthinae 的单系性，与 Pontostratiotinae 姐妹关系。
我们的 DNA 系统发育揭示了 Aegisthidae 的深海起源，将底栖的 Aegisthidae gen.1 和 Cerviniellinae 亚科 nov. 置于最基础的分支。深海海底生物、浮游生物以及相关的生活方式的次生适应性在这里分别通过 Pontostratiotinae、Aegisthinae 和 Siphonis 的衍生位置被发现。
