Fine Michael L, Lahiri Shweta, Sullivan Amanda D H, Mayo Mark, Newton Scott H, Sismour Edward N
Department of Biology, Virginia Commonwealth University, Richmond, Virginia, 23284.
Evolution. 2014 Jul;68(7):2102-7. doi: 10.1111/evo.12379. Epub 2014 Mar 20.
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 likely accounts for smaller pectoral growth in domesticated Channel Catfish. Decreasing spine growth in older fish suggests anti-predator functions are most important in smaller fish. Additionally, growth of the appendicular and axial skeleton is controlled differentially, and mechanical properties of the spine and not just its length are an important component of this defensive adaptation.
斑点叉尾鮰的胸鳍硬棘长度超过鱼体宽度的两倍，这使得口裂有限的捕食者在吞食时变得复杂。硬棘与胸带相连，胸带是一个坚固的结构，用于固定硬棘。本研究表明，硬棘和胸带均呈现负异速生长，并且养殖斑点叉尾鮰的胸鳍硬棘和胸带比野生斑点叉尾鮰的更轻。这一发现可以通过驯化过程中硬棘生长选择压力的变化来解释，或者通过一种表观遗传效应来解释，即野生鱼类暴露于捕食者会刺激胸鳍生长。我们通过将养殖的斑点叉尾鮰幼鱼暴露于大口黑鲈捕食者13周来检验表观遗传假说。幼鱼的硬棘和胸带呈等速生长，回归分析表明，对照鱼和暴露于捕食者的鱼在胸鳍生长比例上没有差异。因此，选择压力的变化可能是养殖斑点叉尾鮰胸鳍生长较小的原因。老龄鱼硬棘生长的减少表明反捕食功能在幼鱼中最为重要。此外，附肢骨骼和轴向骨骼的生长受到不同的控制，硬棘的机械性能而非仅仅其长度是这种防御适应的重要组成部分。
