Reduction of the pectoral spine and girdle in domesticated Channel Catfish is likely caused by changes in selection pressure

Locked pectoral spines of the Channel Catfish Ictalurus punctatus more than double the fish’s width and complicate ingestion by gape-limited predators. The spine mates with the pectoral girdle, a robust structure that anchors the spine. This study demonstrates that both spine and girdle exhibit negative allometric growth and that pectoral spines and girdles are lighter in domesticated than in wild Channel Catfish. This finding could be explained by changes in selection pressure for spine growth during domestication or by an epigenetic effect in which exposure to predators in wild fish stimulates pectoral growth. We tested the epigenetic hypothesis by exposing domesticated Channel Catfish fingerlings to Largemouth Bass Micropterus salmoides predators for 13 weeks. Spines and girdles grow isometrically in the fingerlings, and regression analysis indicates no difference in proportional pectoral growth between control and predator-exposed fish. Therefore a change in selection pressure likel...斑点叉尾鮰（Ictalurus punctatus）的锁合胸棘（pectoral spines）长度可达其体宽的两倍以上，会使口裂受限的捕食者难以将其吞食。胸棘与胸带（pectoral girdle）相连，胸带是一种稳固的结构，用于固定胸棘。本研究表明，胸棘与胸带均呈现负异速生长（negative allometric growth），且驯养型斑点叉尾鮰的胸棘与胸带重量轻于野生种群。该研究结果可通过两种机制解释：一是驯养过程中胸棘生长相关选择压力的改变，二是表观遗传效应（epigenetic effect）——野生个体暴露于捕食者环境下会刺激胸棘生长。为验证表观遗传假说，本研究将驯养型斑点叉尾鮰稚鱼暴露于大口黑鲈（Micropterus salmoides）捕食环境中长达13周。稚鱼的胸棘与胸带呈等速生长（isometric growth），回归分析显示，对照组与捕食者暴露组的胸棘比例生长并无差异。因此，选择压力的改变很可能……