Oomycetes infecting diatoms are biotrophic parasitoids and live in both marine and freshwater environments. They are ubiquitous, but the taxonomic affinity of many species remains unclear and the majority of them have not been studied for their molecular phylogeny. Only recently, the phylogenetic and taxonomic placement of some diatom-infecting, early-diverging oomycetes was resolved, including the genera Ectrogella, Miracula, Olpidiopsis, and Pontisma. A group of holocarpic diatom parasitoids with zoospores swarming within the sporangium before release were found to be unrelated to the known genera with diatom-infecting species, and were re-classified to a new genus, Diatomophthora. However, about a dozen species of holocarpic diatom parasitoids with unclear affinity remained unsequenced, which includes a commonly occurring species so far identified as Ectrogella perforans. However, this assignment to Ectrogella is doubtful, as the species was not reported to feature a clear-cut diplanetism, a hallmark of Ectrogella s. str. and the whole class Saprolegniomycetes. It was the aim of the current study to clarify the phylogenetic affinities of the species and if the rather broad host range reported is correct or a reflection of cryptic species. By targeted screening, the parasitoid was rediscovered from Helgoland Roads, North Sea and Oslo Fjord, Southern Norway and investigated for its phylogenetic placement using small ribosomal subunit (18S) sequences. Stages of its life cycle on different marine diatoms were described and its phylogenetic placement in the genus Diatomophthora revealed. A stable host-parasite axenic culture from single spore strains of the parasitoid were established on several strains of Pleurosigma intermedium and Coscinodiscus concinnus. These have been continuously cultivated along with their hosts for more than 2 years, and cultural characteristics are reported. Cross-infection trials revealed the transferability of the strains between hosts under laboratory conditions, despite some genetic distance between the pathogen strains. Thus, we hypothesise that D. perforans might be in the process of active radiation to new host species.

中文翻译：

---

全掌卵菌硅藻硅藻的系统发育和栽培。十一月，海洋硅藻的内寄生物

感染硅藻的卵菌是生物营养性寄生虫，生活在海洋和淡水环境中。它们无处不在，但许多物种的分类学亲和力仍不清楚，并且大多数分子的系统发育尚未进行研究。直到最近，进化和一些硅藻感染，早期发散卵菌分类地位得到了解决，其中包括属Ectrogella，Miracula，Olpidiopsis和Pontisma。发现一组散发在孢子囊内的游动孢子的全硅藻硅藻类寄生虫与已知的硅藻感染种无关，并被重新分类为新属硅藻。。然而，大约十二种具有不清楚亲和力的全硅藻硅藻类寄生虫仍未排序，其中包括一种迄今被鉴定为穿孔小球藻的常见物种。但是，这种对小球藻的鉴定是值得怀疑的，因为据报道该物种没有明显的双行星现象，这是小球藻的标志。s。海峡 和整个类的腐生菌。当前研究的目的是弄清该物种的系统进化亲和力，以及所报道的相当宽的寄主范围是正确的还是隐性物种的反映。通过有针对性的筛选，从北海的Helgoland Roads和挪威南部的奥斯陆峡湾重新发现了该类寄生虫，并使用小的核糖体亚基（18S）序列对其寄生虫进行了系统发育研究。描述了其在不同海洋硅藻上的生命周期阶段，并揭示了其在硅藻属属中的系统发育位置。在几种中间球孢菌和协球菌上建立了稳定的寄主寄生虫寄生虫厌氧菌培养物。。这些与它们的寄主一起被连续种植了两年多，据报道其文化特征。交叉感染试验表明，尽管病原体之间存在一定的遗传距离，但它们在实验室条件下仍可在宿主之间转移。因此，我们假设D. perforans可能正在向新的寄主物种主动辐射。