German Donovan P, Nagle Brett C, Villeda Jennette M, Ruiz Ana M, Thomson Alfred W, Contreras Balderas Salvador, Evans David H
Department of Biology, University of Florida, Gainesville, Florida 32611, USA.
Physiol Biochem Zool. 2010 Jan-Feb;83(1):1-18. doi: 10.1086/648510.
We constructed a phylogeny for 10 minnow species (family Cyprinidae) previously revealed to be members of sister genera with different dietary affinities and used the phylogeny to examine whether the evolution of digestive tract size and physiology is correlated with the evolution of diet in these fishes. We studied a total of 11 taxa: four herbivorous species in the genus Campostoma and six largely carnivorous species in the genus Nocomis, including two populations of Nocomis leptocephalus, the carnivorous Chattahoochee River drainage population and the herbivorous Altamaha River drainage population. Thus, we were able to compare digestive tract size and physiology among sister genera (Campostoma and Nocomis) and among sister taxa (N. leptocephalus Chattahoochee and N. leptocephalus Altamaha) in dietary and phylogenetic contexts. The herbivorous taxa had longer digestive tracts and higher activity of the carbohydrases amylase and laminarinase in their guts, whereas the carnivorous species had higher chitinase activity. Phylogenetic independent-contrast analysis suggested that the evolution of amylase and chitinase activities was correlated with the evolution of diet in these species, whereas trypsin and lipase activities showed no pattern associated with diet or phylogenetic history. Concentrations of short-chain fatty acids were low in all taxa, indicating that these fishes rely largely on endogenous digestive mechanisms to subsist on their respective diets. Subtle differences in tooth shape were observed between species in the two genera. Overall, our results suggest that dietary specialization can be observed on the level of anatomy and physiology of the digestive tracts of fishes but that such differences are most appropriately viewed in comparisons of closely related species with different diets.
我们构建了一个系统发育树，涉及10种米诺鱼（鲤科），先前已揭示它们是具有不同食性的姐妹属的成员，并利用该系统发育树来研究这些鱼类消化道大小和生理机能的进化是否与饮食进化相关。我们总共研究了11个分类单元：Campostoma属的4种草食性物种和Nocomis属的6种主要肉食性物种，包括Nocomis leptocephalus的两个种群，即肉食性的查塔胡奇河排水区种群和草食性的阿尔塔马哈河排水区种群。因此，我们能够在饮食和系统发育背景下，比较姐妹属（Campostoma和Nocomis）之间以及姐妹分类单元（查塔胡奇河的N. leptocephalus和阿尔塔马哈河的N. leptocephalus）之间的消化道大小和生理机能。草食性分类单元的消化道更长，肠道中碳水化合物酶淀粉酶和海带多糖酶的活性更高，而肉食性物种的几丁质酶活性更高。系统发育独立对比分析表明，淀粉酶和几丁质酶活性的进化与这些物种的饮食进化相关，而胰蛋白酶和脂肪酶活性则未显示出与饮食或系统发育历史相关的模式。所有分类单元中的短链脂肪酸浓度都很低，这表明这些鱼类在很大程度上依赖内源性消化机制来依靠各自的食物生存。在这两个属的物种之间观察到牙齿形状的细微差异。总体而言，我们的结果表明，在鱼类消化道的解剖学和生理学水平上可以观察到饮食特化，但这种差异在比较具有不同饮食的近缘物种时最能得到恰当的体现。
