Data from: Genetic and environmental effects on the morphological asymmetry in the scale-eating cichlid fish, Perissodus microlepis

The scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika are a well-known example of an asymmetry dimorphism because the mouth/head is either left-bending or right-bending. However, how strongly its pronounced morphological laterality is affected by genetic and environmental factors remains unclear. Using quantitative assessments of mouth asymmetry, we investigated its origin by estimating narrow-sense heritability (h2) using midparent–offspring regression. The heritability estimates [field estimate: h2 = 0.22 ± 0.06, P = 0.013; laboratory estimate: h2 = 0.18 ± 0.05, P = 0.004] suggest that although variation in laterality has some additive genetic component, it is strongly environmentally influenced. Family-level association analyses of a putative microsatellite marker that was claimed to be linked to gene(s) for laterality revealed no association of this locus with laterality. Moreover, the observed phenotype frequencies in offspring from parents of different phenotype combinations were not consistent with a previously suggested single-locus two-allele model, but they neither were able to reject with confidence a random asymmetry model. These results reconcile the disputed mechanisms for this textbook case of mouth asymmetry where both genetic and environmental factors contribute to this remarkable case of morphological asymmetry.来自坦噶尼喀湖（Lake Tanganyika）的食鳞慈鲷（scale-eating cichlid fish，*Perissodus microlepis*）是不对称二态性（asymmetry dimorphism）的知名范例，其口部与头部呈现左偏或右偏的形态特征。然而，其显著的形态侧向性（morphological laterality）受遗传与环境因素的影响程度目前仍未明确。本研究通过对口腔不对称性开展定量评估，采用双亲-后代回归法（midparent–offspring regression）估算狭义遗传力（narrow-sense heritability，h²），以此探究该性状的起源。遗传力估算结果[野外估算：h² = 0.22 ± 0.06, P = 0.013；实验室估算：h² = 0.18 ± 0.05, P = 0.004]表明，尽管侧向性变异存在一定的加性遗传组分，但该性状仍受环境因素的强烈影响。针对此前声称与侧向性相关基因连锁的推定微卫星标记（microsatellite marker）进行家系水平关联分析，结果未发现该位点与侧向性存在关联。此外，不同表型组合亲本的后代所观测到的表型频率，与此前提出的单基因双等位基因模型（single-locus two-allele model）并不相符，但也无法确切驳斥随机不对称模型（random asymmetry model）。本研究结果为这一经典教科书级口腔不对称案例的争议机制提供了调和依据——遗传与环境因素共同参与塑造了这一极具特色的形态不对称现象。