RESUMO
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.
Assuntos
Cyprinidae/fisiologia , Evolução Molecular , Trato Gastrointestinal/fisiologia , Amilases/fisiologia , Animais , Celulases/fisiologia , Quitinases/fisiologia , Cyprinidae/anatomia & histologia , Cyprinidae/genética , Citocromos b/química , Citocromos b/genética , DNA/química , DNA/genética , Fenômenos Fisiológicos do Sistema Digestório/genética , Proteínas do Olho/química , Proteínas do Olho/genética , Conteúdo Gastrointestinal/química , Conteúdo Gastrointestinal/enzimologia , Trato Gastrointestinal/anatomia & histologia , Trato Gastrointestinal/enzimologia , Microscopia Eletrônica de Varredura , Filogenia , Reação em Cadeia da Polimerase , Proteínas de Ligação ao Retinol/química , Proteínas de Ligação ao Retinol/genética , Rodopsina/química , Rodopsina/genética , Análise de Sequência de DNA , Dente/anatomia & histologia , Dente/ultraestruturaRESUMO
Dr. Contreras Balderas is Professor Emeritus in the Department of Biology at Universidad Autonoma de Nuevo Leon (Monterrey, Mexico). He received a Master's degree and Ph.D. in Biological Sciences from Tulane University (New Orleans, LA) and wrote his dissertation on Ichthyology. He was awarded the President's Excellence Award of the American Fisheries Society. Dr. Contreras Balderas is Founder, President, and Honorary Member of the Mexican Society of Zoology, the Ichthyological Society of Mexico, and the Desert Fishes Council, is an ex-officio member of the Coalition for the Sustainable Development of the Rio Grande/Rio Bravo, U.S. & Mexico, and is a member of the U.S. Fish and Wildlife's Rio Grande Fishes Recovery Team. Dr. Contreras Balderas's areas of expertise include fish faunas, fishes at risk, exotic species, aquatic restoration, environmental impacts as detected by fishes, integral conservation, integral basin/ecosystem management, and ecological evaluation of integrity in basins.
