Abstract

Obligate endoparasitic oomycetes are known to ubiquitously occur in marine and freshwater diatoms, but their diversity is still largely unexplored. Many of these parasitoids are members of the early-diverging oomycete lineages (Miracula, Diatomophthora), others are within the Leptomitales of the Saprolegniomycetes (Ectrogella, Lagenisma) and some have been described in the Peronosporomycetes (Aphanomycopsis, Lagenidium). Even though some species have been recently described and two new genera were introduced (Miracula and Diatomophthora), the phylogeny and taxonomy of most of these organisms remain unresolved. This is contrasted by the high number of sequences from unclassified species, as recently revealed from environmental sequencing, suggesting the presence of several undiscovered species. In this study, a new species of Miracula is reported from a marine centric diatom (Minidiscus sp.) isolated from Skagaströnd harbor in Northwest Iceland. The morphology and life cycle traits of this novel oomycete parasite are described herein, and its taxonomic placement within the genus Miracula is confirmed by molecular phylogeny. As it cannot be assigned to any previously described species, it is introduced as Miracula islandica in this study. The genus Miracula thus contains three described holocarpic species (M. helgolandica, M. islandica, M. moenusica) to which likely additional species will need to be added in the future, considering the presence of several lineages known only from environmental sequencing that clustered within the Miracula clade.

摘要

众所周知，专性内寄生卵菌普遍存在于海洋和淡水硅藻中，但它们的多样性在很大程度上仍未得到探索。许多这些寄生蜂是早期发散卵菌谱系（成员Miracula，Diatomophthora），其他都是中Leptomitales中的Saprolegniomycetes（Ectrogella，Lagenisma）和一些已经在被描述Peronosporomycetes（Aphanomycopsis，链壶）。尽管最近描述了一些物种并引入了两个新属（奇迹属和硅藻属）)，大多数这些生物的系统发育和分类学仍未解决。这与来自未分类物种的大量序列形成鲜明对比，正如最近从环境测序中揭示的那样，这表明存在几种未被发现的物种。在这项研究中，从冰岛西北部 Skagaströnd 港口分离的海洋中心硅藻 ( Minidiscus sp.)报告了一种新的奇迹。本文描述了这种新型卵菌寄生虫的形态和生命周期特征，其在Miracula属中的分类位置由分子系统发育证实。由于它不能分配给任何先前描述的物种，因此在本研究中将其作为Miracula islandica引入。属Miracula因此包含三个描述的全果种（M. helgolandica , M. islandica , M. moenusica），考虑到存在几个仅从环境测序中已知的谱系聚集在Miracula内，未来可能需要添加其他物种进化枝。