PDF(Pubmed)
Abstract：
Aratus pisonii and Minuca rapax are two brachyuran crabs living with bacterial ectosymbionts located on gill lamellae. One previous study has shown that several rod-shaped bacterial morphotypes are present and the community is dominated by Alphaproteobacteria and Bacteroidota. This study aims to identify the mode of transmission of the symbionts to the new host generations and to identify the bacterial community colonizing the gills of juveniles. We tested for the presence of bacteria using PCR with universal primers targeting the 16S rRNA encoding gene from gonads, eggs, and different larval stages either obtained in laboratory conditions or from the field. The presence of bacteria on juvenile gills was also characterized by scanning electron microscopy, and subsequently identified by metabarcoding analysis. Gonads, eggs, and larvae were negative to PCR tests, suggesting that bacteria are not present at these stages in significant densities. On the other hand, juveniles of both species display three rod-shaped bacterial morphotypes on gill lamellae, and sequencing revealed that the community is dominated by Bacteroidota and Alphaproteobacteria on A. pisonii juveniles, and by Alphaprotobacteria, Bacteroidota, and Acidimicrobia on M. rapax juveniles. Despite the fact that juveniles of both species co-occur in the same biotope, no shared bacterial phylotype was identified. However, some of the most abundant bacteria present in adults are also present in juveniles of the same species, suggesting that juvenile-associated communities resemble those of adults. Because some of these bacteria were also found in crab burrow water, we hypothesize that the bacterial community is established gradually during the life of the crab starting from the megalopa stage and involves epibiosis-competent bacteria that occur in the environment.
摘要：
Aratuspisonii和Minucarapax是两种短尾蟹，它们与位于g薄片上的细菌外共生体一起生活。先前的一项研究表明，存在几种杆状细菌形态类型，并且该群落以α变形杆菌和拟杆菌属为主。这项研究旨在确定共生体向新宿主世代的传播方式，并确定在幼体g中定植的细菌群落。我们使用PCR测试了细菌的存在，使用通用引物靶向性腺16SrRNA编码基因，鸡蛋,以及在实验室条件下或从田间获得的不同幼虫阶段。通过扫描电子显微镜还可以表征幼鱼上细菌的存在，随后通过元编码分析识别。性腺,鸡蛋,幼虫PCR检测呈阴性，这表明细菌在这些阶段并不以显著的密度存在。另一方面,这两个物种的幼虫在g薄片上都显示出三种杆状细菌形态，测序显示，该群落主要由比松杆菌属幼体上的拟杆菌和阿尔法变形杆菌，通过阿尔法原细菌，拟杆菌,和酸性微生物对M.rapax青少年。尽管两个物种的幼体在同一生物群落中共存，未发现共有的细菌表型.然而,成人中存在的一些最丰富的细菌也存在于同一物种的少年中，这表明与青少年相关的社区类似于成年人。因为这些细菌中的一些也在螃蟹洞穴水中发现，我们假设，细菌群落是在蟹的生命过程中逐渐建立的，从megalopa阶段开始，并涉及环境中出现的具有表观生能力的细菌。
