Early holobiont-level divergence and adaptation across seafloor geochemical contrasts in the deep-sea squat lobster Shinkaia crosnieri.

Deep-sea squat lobster Shinkaia crosnieri shows early-stage divergence driven by habitat-specific host genomics and symbiont composition across geochemical contrasts.

• Why it matters: Understanding how environmental geochemistry and host-microbe interactions jointly influence evolutionary processes in chemosynthetic ecosystems remains limited, hindering insights into biodiversity in extreme habitats.
• What they did: The study combined host genomics, population resequencing, and episymbiont metagenomics in S. crosnieri populations from hydrothermal vents and methane seeps, revealing genetic divergence and habitat-specific symbiont recruitment.
• The result: Findings suggest that holobiont-wide adaptation, involving host genomic plasticity and symbiont metabolic specialization, underpins early divergence driven by geochemical gradients, enabling niche partitioning and energy metabolism differentiation.