Shift in bacterial taxa precedes morphological plasticity in a larval echinoid

Morphological plasticity is an adaptive response to heterogenous environments when a fitness advantage is conferred. Larval sea urchins, for example, increase individual fitness in dilute feeding environments by elongating their feeding structure. Morphological plasticity for larval sea urchins is also coupled with significant shifts in the associated bacterial community, but whether this response occurs before, during, or following the expression of plasticity is unclear. Using the sea urchin Lytechinus variegatus, we define the temporal pattern of the associated bacterial community throughout the expression of morphological plasticity. From prefeeding through plasticity, we observed that L. variegatus larvae exhibit a four-stage successional pattern and the relatedness of the larval-associated bacterial community directly reflects morphological plasticity and does so prior to expression of the environmental-specific morphology. Based on the structure of the larval-associated bacterial...形态可塑性（Morphological plasticity）是当生物获得适合度优势时，对异质环境产生的适应性响应。例如，海胆幼虫可通过延长取食结构，在稀薄饵料环境中提升个体适合度。海胆幼虫的形态可塑性还会伴随其共生细菌群落的显著变化，但目前尚不清楚这类响应是发生在可塑性表达之前、期间还是之后。本研究以杂色海胆（Lytechinus variegatus）为实验材料，明确了形态可塑性表达全过程中其共生细菌群落的时间动态模式。从预取食阶段至可塑性表达阶段，我们观察到杂色海胆幼虫的共生细菌群落呈现四阶段演替模式，且幼虫共生菌群的亲缘关系直接反映了形态可塑性——这一关联甚至早于环境特异性形态的表达。基于幼虫共生细菌群落的结构……