Geographic and seasonal variation analysis of digestive morphology in the catfish Iheringichthys labrosus along lower Río Uruguay

Alejandro D'Anatro,¹ Nicolás Vidal,^2–4 Iván González-Bergonzoni,^2–4 Franco Teixeira de Mello,⁴ Jukka Tana,⁵ Daniel E Naya<sup>1

1</sup>Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay; ²Department of Bioscience, Aarhus University, Silkeborg, Denmark; ³Sino-Danish Centre for Education and Research (SDC), Beijing, People's Republic of China; ⁴Grupo de Ecología y Rehabilitación de Sistemas Acuáticos, Departamento de Ecología y Evolución, CURE-Facultad de Ciencias, Universidad de la República, Maldonado, Uruguay; ⁵ÅF-Consult Ltd, Environmental Consulting, Espoo, Finland

Abstract: The study of geographic variation of individual traits is an important component of evolutionary research, in that individual morphological features can be subjected to multiple selective pressures. The present work is aimed to analyze the geographic and seasonal variation in several digestive traits in Iheringichthys labrosus along three localities in the lower Río Uruguay. Statistically significant differences among locations and between seasons were found for all the variables assessed, the most noticeable of differences being observed were intestinal length, intestine weight, and liver weight. In part, these differences could be an adaptive response to changes in food availability and/or in the energetic costs of reproduction. Results obtained herein also suggest that individuals of this species spend enough time in each locality as to show a consistent response to local conditions in their digestive traits morphology.

Keywords: Iheringichthys labrosus, physiological flexibility, Río Uruguay