Microbial symbionts are a common life-history character of marine invertebrates and their developmental stages. Communities of bacteria that associate with the eggs, embryos, and larvae of coastal marine invertebrates tend to be species specific and correlate with aspects of host biology and ecology. The richness of bacteria associated with the developmental stages of coastal marine invertebrates spans four orders of magnitude, from single mutualists to thousands of unique taxa. This understanding stems predominately from the developmental stages of coastal species. If they are broadly representative of marine invertebrates, then we may expect deep-sea species to associate with bacterial communities that are similar in diversity. To test this, we used amplicon sequencing to profile the bacterial communities of invertebrate larvae from multiple taxonomic groups (annelids, molluscs, crustaceans) collected from 2500 to 3670 m in depth in near-bottom waters near hydrothermal vents in 3 different regions of the Pacific Ocean (the East Pacific Rise, the Mariana Back-Arc, and the Pescadero Basin). We find that larvae of deep-sea invertebrates associate with low-diversity bacterial communities (~30 bacterial taxa) that lack specificity between taxonomic groups. The diversity of these communities is estimated to be ~7.9 times lower than that of coastal invertebrate larvae, but this result depends on the taxonomic group. Associating with a low-diversity community may imply that deep-sea invertebrate larvae do not have a strong reliance on a microbiome and that the hypothesized lack of symbiotic contributions would differ from expectations for larvae of coastal marine invertebrates.

中文翻译：

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深海无脊椎动物幼虫拥有低多样性细菌群落

微生物共生体是海洋无脊椎动物及其发育阶段的共同生活史特征。与沿海海洋无脊椎动物的卵、胚胎和幼虫相关的细菌群落往往具有物种特异性，并与宿主生物学和生态学的各个方面相关。与沿海海洋无脊椎动物的发育阶段相关的细菌丰富度跨越四个数量级，从单一的共生者到数千种独特的分类群。这种理解主要源于沿海物种的发育阶段。如果它们广泛代表海洋无脊椎动物，那么我们可能会期望深海物种与多样性相似的细菌群落相关联。为了测试这个，我们使用扩增子测序分析了来自多个分类群（环节​​动物、软体动物、甲壳类动物）的无脊椎动物幼虫的细菌群落，这些分类群是从 2500 到 3670 米深的太平洋（东部）热液喷口附近的近底水域收集的太平洋隆起、马里亚纳弧后弧和佩斯卡德罗盆地）。我们发现深海无脊椎动物的幼虫与在分类群之间缺乏特异性的低多样性细菌群落（约 30 个细菌分类群）相关联。这些群落的多样性估计比沿海无脊椎动物幼虫的多样性低约 7.9 倍，但这一结果取决于分类群。