Gregarines, a polyphyletic group of apicomplexan parasites infecting mostly non‐vertebrates hosts, remains poorly known at taxonomic, phylogenetic and genomic levels. However, it represents an essential group for understanding evolutionary history and adaptive capacities of apicomplexan parasites to the remarkable diversity of their hosts. Because they have a mostly extracellular lifestyle, gregarines have developed other cellular developmental forms and host–parasite interactions, compared with their much better studied apicomplexan cousins, intracellular parasites of vertebrates (Hemosporidia, Coccidia, Cryptosporidia). This review highlights the promises offered by the molecular exploration of gregarines, that have been until now left on the side of the road of the comparative –omic exploration of apicomplexan parasites. Elucidating molecular bases for both their ultrastructural, functional and behavioural similarities and differences, compared with those of the typical apicomplexan models, is expected to provide entirely novel clues on the adaptive capacities developed by Apicomplexa over evolution. A challenge remains to identify which gregarines should be explored in priority, as recent metadata from open and host‐associated environments have confirmed how underestimated is our current view on true gregarine biodiversity. It is now time to turn to gregarines to widen the currently highly skewed view we have of adaptive mechanisms developed by Apicomplexa.

中文翻译：

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为什么 Apicomplexa 的组学未来应该包括 Gregarines

Gregarines 是一种多系群的顶复门寄生虫，主要感染非脊椎动物宿主，在分类学、系统发育和基因组水平上仍然知之甚少。然而，它代表了理解顶复门寄生虫对其宿主显着多样性的进化历史和适应能力的重要群体。由于它们主要是细胞外生活方式，因此与它们更好地研究的顶复类表亲、脊椎动物的细胞内寄生虫（血孢子虫、球虫、隐孢子虫）相比，群居动物已经发展出其他细胞发育形式和宿主 - 寄生虫相互作用。这篇综述强调了对 gregarines 的分子探索所带来的希望，直到现在，它们仍被搁置在对顶复门寄生虫进行比较组学探索的道路上。与典型的 apicomplexan 模型相比，阐明其超微结构、功能和行为异同的分子基础有望为 Apicomplexa 在进化过程中开发的适应能力提供全新的线索。一个挑战仍然是确定应该优先探索哪些群落，因为最近来自开放和宿主相关环境的元数据证实了我们目前对真正的群落生物多样性的看法被低估了。现在是时候转向 gregarines 来扩大我们目前对 Apicomplexa 开发的自适应机制的高度倾斜的看法。预计将为 Apicomplexa 在进化过程中开发的适应能力提供全新的线索。一个挑战仍然是确定应该优先探索哪些群落，因为最近来自开放和宿主相关环境的元数据证实了我们目前对真正的群落生物多样性的看法被低估了。现在是时候转向 gregarines 来扩大我们目前对 Apicomplexa 开发的自适应机制的高度倾斜的看法。预计将为 Apicomplexa 在进化过程中开发的适应能力提供全新的线索。一个挑战仍然是确定应该优先探索哪些群落，因为最近来自开放和宿主相关环境的元数据证实了我们目前对真正的群落生物多样性的看法被低估了。现在是时候转向 gregarines 来扩大我们目前对 Apicomplexa 开发的自适应机制的高度倾斜的看法。