Challengerids, phaeogromids rhizarian protists, are emblematic protists of the deep sea but are also enigmatic as they occur in very low concentrations. In previous studies, we reported on temporal changes in abundance at a near-shore mesopelagic site, but only as part of sampling of the entire microplankton assemblage, not well-suited for examining phaeogromids. Consequently, we turned to using a closing plankton net to provide material from large volumes of seawater, thus allowing for more robust estimates of concentrations and material for observations of living cells, to our knowledge the first made. Here, we report our results on the four most commonly occurring species: Challengeranium diadon, Challengereron willemoesii, Challengeria xiphodon, and Euphysetta lucani. In contrast to our previous report, we found that changes in concentrations were not related to water column stratification, and the four species roughly co-varied with time. Observations of live cells revealed that all four species deploy tentacle-like pseudopods and also very large unstructured webs of fine pseudopods. The similarities in feeding webs suggest similar prey are exploited, and the similar temporal changes in abundances suggest a common factor or factors (unknown at this time) govern their concentrations. Films of live cells are provided in Supplementary Files.

中文翻译：

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中远洋海洋浮游生物的 Phaeogromids：浓度的时间变化和地中海中远洋四种物种摄食结构的观察

Challengerids，phaeogromids rhizarian 原生生物，是深海的标志性原生生物，但也很神秘，因为它们的浓度非常低。在以前的研究中，我们报告了近岸中远洋地点丰度的时间变化，但仅作为整个微型浮游生物组合的一部分，不太适合检查 phaeogromids。因此，据我们所知，我们转而使用封闭的浮游生物网从大量海水中提供材料，从而可以更可靠地估计浓度和用于观察活细胞的材料。在这里，我们报告了四种最常出现的物种的结果：Challengeranium diadon、Challengereron willemoesii、Challengeria xiphodon和Euphysetta lucani。与我们之前的报告相反，我们发现浓度的变化与水柱分层无关，并且这四种物种大致随时间共同变化。对活细胞的观察表明，所有四种物种都部署了触手状伪足和非常大的非结构化细伪足网。喂食网的相似性表明类似的猎物被利用，丰度的相似时间变化表明一个或多个共同因素（目前未知）控制着它们的浓度。补充文件中提供了活细胞的电影。