The microbiota, the host-associated community of microbes, play important roles in health status and whole body homeostasis of all organisms, including marine species. In bivalves, the microbiota composition has been mainly investigated in adults, whereas little information is available during development.

In this work, the microbiota composition of the first larval stages of Mytilus galloprovincialis was evaluated by 16S rRNA gene-based profiling, at 24 and 48 hours post fertilization in comparison with those of eggs and sperm. The main genera detected in both larvae (Vibrio, Pseudoalteromonas, Psychrobium, Colwellia) derived from eggs. However, a clear shift in microbiota was observed in developing larvae compared to eggs, both in terms of core microbiome and relative abundance of different genera. The results provide a first insight into the composition of the microbial communities associated with gametes and early larvae of mussels.

Moreover, the impact on larval microbiome of estrogenic chemicals that potentially affect Mytilus early development, 17βestradiol-E₂, Bisphenol A-BPA and Bisphenol F-BPF (10 μg/L), was investigated. Exposure to estrogenic chemicals leads to changes in abundance of different genera, with distinct and common effects depending on the compound and larval stage. Both potential pathogens (Vibrio, Arcobacter, Tenacibaculum) and genera involved in xenobiotic biotransformation (Oleispira, Shewanella) were affected. The effects of estrogenic compounds on larval microbiome were not related to their developmental effects: however, the results address the importance of evaluating the impact of emerging contaminants on the microbiota of marine invertebrates, including larval stages, that are most sensitive to environmental perturbations.

微生物群是与宿主相关的微生物群落，在包括海洋物种在内的所有生物的健康状况和全身稳态中起着重要作用。在双壳类动物中，主要在成虫中研究了微生物群组成，而在发育过程中几乎没有信息。

在这项工作中，与受精后的卵和精子相比，在受精后24和48小时通过基于16S rRNA基因的基因分析评估了盖氏菌Mytilus galloprovincialis幼虫第一阶段的微生物群组成。主属在两个幼虫（检测弧菌，假交替单胞，Psychrobium，Colwellia）从鸡蛋衍生。然而，就核心微生物组和不同属的相对丰度而言，与卵相比，发育中的幼虫的微生物群发生了明显变化。结果提供了对与贻贝的配子和早期幼虫有关的微生物群落组成的初步见解。

此外，研究了可能影响Mytilus早期发育的雌激素化学物质对幼虫微生物组的影响，其中17β-雌二醇-E ₂，双酚A-BPA和双酚F-BPF（10μg/ L）。暴露于雌激素化学物质会导致不同属的丰度发生变化，具体取决于化合物和幼虫的阶段，会产生不同而普遍的影响。这两个潜在的病原体（弧菌，弓形，黏着）和属参与外源性生物转化（Oleispira，希瓦氏菌）受到影响。雌激素化合物对幼虫微生物组的影响与它们的发育作用无关：但是，该结果解决了评估新兴污染物对海洋无脊椎动物（包括幼虫阶段）微生物群的影响的重要性，其中，该无脊椎动物对环境扰动最敏感。