Department of Biology, University of Florence, 50019, Sesto Fiorentino, Italy.
The Swire Institute of Marine Science, The University of Hong Kong, Hong Kong, Hong Kong SAR, People's Republic of China.
Sci Rep. 2023 Nov 29;13(1):21033. doi: 10.1038/s41598-023-48308-w.
Transitions to physically different environments, such as the water-to-land transition, proved to be the main drivers of relevant evolutionary events. Brachyuran crabs evolved remarkable morphological, behavioral, and physiological adaptations to terrestrial life. Terrestrial species evolved new respiratory structures devoted to replace or support the gills, a multifunctional organ devoted to gas exchanges, ion-regulation and nitrogen excretion. It was hypothesized that microorganisms associated with respiratory apparatus could have facilitated the processes of osmoregulation, respiration, and elimination of metabolites along this evolutionary transition. To test if crab species with different breathing adaptations may host similar microbial communities on their gills, we performed a comparative targeted-metagenomic analysis, selecting two marine and six terrestrial crabs belonging to different families and characterised by different breathing adaptations. We analysed anterior and posterior gills separately according to their different and specific roles. Regardless of their terrestrial or marine adaptations, microbial assemblages were strongly species-specific indicating a non-random association between the host and its microbiome. Significant differences were found in only two terrestrial species when considering posterior vs. anterior gills, without any association with species-specific respiratory adaptations. Our results suggest that all the selected species are strongly adapted to the ecological niche and specific micro-habitat they colonise.
过渡到物理性质不同的环境，如从水到陆的过渡，被证明是相关进化事件的主要驱动因素。短尾类螃蟹进化出了显著的形态、行为和生理适应来适应陆地生活。陆生物种进化出了新的呼吸结构，用于替代或支持鳃，鳃是一个多功能器官，用于气体交换、离子调节和氮排泄。据推测，与呼吸器官相关的微生物可能促进了渗透调节、呼吸和代谢物排泄的过程，从而促成了这种进化过渡。为了测试具有不同呼吸适应能力的螃蟹物种是否可能在其鳃上拥有相似的微生物群落，我们进行了一项比较靶向宏基因组分析，选择了两种海洋蟹和六种陆地蟹，它们属于不同的科，具有不同的呼吸适应能力。我们根据不同的功能和特定角色分别分析了前鳃和后鳃。无论它们是适应陆地还是海洋，微生物群落都具有很强的物种特异性，表明宿主与其微生物组之间存在非随机关联。仅在考虑后鳃和前鳃时，在两种陆地物种中发现了显著差异，但与物种特异性呼吸适应无关。我们的结果表明，所有选定的物种都强烈适应其栖息的生态位和特定的小生境。
