Data from: The microbiota of diapause: how host-microbe associations are formed after dormancy in an aquatic crustacean

1. A critical question in symbiosis research is where and how organisms obtain beneficial microbial symbionts in different ecological contexts. Microbiota of juveniles are often derived directly from their mother or from the immediate environment. The origin of beneficial symbionts, however, is less obvious in organisms with diapause and dispersal stages, such as plants with dormant seeds and animals in ephemeral or strongly seasonal habitats. In these cases, parents and offspring are separated in time and space, which may affect opportunities for both vertical and horizontal transmission of symbionts. 2. The planktonic crustacean Daphnia produces long-lasting resting eggs to endure winter freezing and summer droughts and requires microbiota for growth and reproduction. It is unknown how hatchlings from resting stages form associations with microbial consorts after diapause. 3. Using natural samples of D. magna resting eggs after several years of storage, we show that the total bacterial community derived from both the exterior and interior of the eggs’ ephippial cases is sufficiently beneficial to ensure normal Daphnia functioning in otherwise bacteria-free conditions. We do not find direct evidence that the required bacteria are of maternal origin, though sequencing reveals that the resting stage is accompanied by bacterial taxa previously found in association with adult animals. 4. These findings suggest that while Daphnia are strongly dependent on environmental bacteria for normal functioning, host-bacteria associations are somewhat general and availability of specific bacteria is not a strong constraint on host ecology. Nevertheless, animals and microbes may be ecologically linked through co-dispersal.

1. 共生研究的核心议题之一，是不同生态背景下生物体如何以及从何处获取有益的微生物共生体（microbial symbionts）。幼体的微生物群通常直接来源于母体或其紧邻的环境，但对于存在滞育与扩散阶段的类群而言——例如拥有休眠种子的植物，以及栖息在短命或强季节性生境中的动物——其有益共生体的来源往往不甚明晰。这类物种的亲代与子代在时间与空间上存在隔离，这可能会影响共生体垂直传播与水平传播的潜在机会。
2. 浮游甲壳动物水蚤（Daphnia）可产生持久的休眠卵以抵御冬季冰冻与夏季干旱，其生长与繁殖依赖于共生微生物群。目前学界尚未明确，滞育阶段结束后孵化的幼体，如何与微生物群落建立共生关联。
3. 本研究以储存数年的大型溞（D. magna）休眠卵自然样本为实验材料，结果显示，从卵鞍外壳内外分离得到的完整细菌群落，足以在无菌培养条件下保障水蚤正常的生理功能。尽管测序分析揭示，滞育阶段的卵伴随有此前在成体水蚤体内发现的细菌类群，但研究未发现所需细菌为母源的直接证据。
4. 上述发现表明，尽管水蚤的正常生理功能高度依赖环境中的细菌，但其与细菌的共生关系具有一定的普遍性，特定细菌的可获得性并不会对宿主的生态特征构成强约束。不过，动物与微生物仍可能通过共同扩散形成生态关联。