Data from: Neglected patterns of variation in phenotypic plasticity: age- and sex-specific antipredator plasticity in a cichlid fish

The ability of organisms to plastically respond to changing environments is well studied. However, variation in phenotypic plasticity during ontogeny is less well understood despite its relevance of being an important source of phenotypic variation in nature. Here, we comprehensively study ontogenetic variation in morphological antipredator plasticity across multiple traits in Pelvicachromis taeniatus, a Western African cichlid fish with sexually dimorphic ornamentation. In a split-clutch design, fish were raised under different levels of perceived predation risk (conspecific alarm cues or distilled water). Morphological plasticity varied substantially across ontogeny: it was first observable at an early juvenile stage where alarm cue-exposed fish grew faster. Subsequently, significant plasticity was absent until the onset of sexual maturity. Here, alarm-cue-exposed males were bigger than control males, which led to deeper bodies, longer dorsal spines, bigger caudal
peduncles and increased eye diameters. Sexual ornamentation emerged delayed in alarm cue-exposed males. In later adulthood, the plastic responses receded. Despite small effect sizes, these responses represent putative adaptive plasticity as they are likely to reduce predation risk. In females, we did not observe any plasticity. In accordance with theory, these results suggest fine-tuned expression of plasticity that potentially increases defenses during vulnerable developmental stages and reproductive output.

生物对变化环境的塑性响应能力已得到充分研究。然而，尽管表型可塑性（phenotypic plasticity）是自然界表型变异的重要来源，个体发育（ontogeny）过程中的表型可塑性变异却仍未得到充分阐释。本研究以西非慈鲷鱼类饰带桨鳍丽鱼（Pelvicachromis taeniatus）——一种具有性二态装饰特征的物种——为研究对象，全面解析其多性状形态学反捕食可塑性的个体发育变异。本研究采用分窝实验设计（split-clutch design），将实验鱼饲养于两种不同感知捕食风险的环境中：分别施加同类告警信号（conspecific alarm cues）或蒸馏水作为对照。形态学可塑性的表达随个体发育进程存在显著差异：该可塑性最早可在早期幼体阶段被观测到，此时暴露于告警信号的幼鱼生长速度更快。此后直至性成熟前，均未观测到显著的形态学可塑性变化。在性成熟阶段，暴露于告警信号的雄性个体体型大于对照组雄性，具体表现为躯体更深、背鳍棘更长、尾柄（caudal peduncle）更粗壮以及眼径更大。暴露于告警信号的雄性个体，其性二态装饰的出现时间延迟。在成年后期，这类塑性响应逐渐消退。尽管效应量较小，但这类响应属于推定的适应性可塑性（adaptive plasticity），因其可有效降低被捕食风险。而在雌性个体中，未观测到任何形态学可塑性变化。本研究结果与理论预期一致，表明可塑性的表达受到精细调控：该调控机制可在个体发育的脆弱阶段提升防御能力，并可能促进繁殖产出。