Diet induces phenotypic plasticity of Percichthys trucha (Valenciennes, 1833) (Perciformes, Percichthyidae) in Patagonia

The South American fish genus Percichthys, due to its great morphological variation, has included several nominal species throughout a long history. However, current genetic analyses signal the existence of only two extant species, Percichthys melanops Girard in Chile (west of the Andes) and P. trucha (Valenciennes) in Chile and Argentina (west and east of the Andes). Here the morphological variation of free embryos, larvae, and juveniles of P. trucha was analyzed using linear measurements and geometric morphometrics. Early morphological variation and compensatory growth were examined using sibling free embryos and larva. Morphological consequences of experimentally controlled food treatments were explored in juveniles. Our results showed individual variation in the size of the yolk-sac of free embryos and in the duration of the mixed feeding period. Phenotypic convergence of the upper jaw length from larva to juveniles and adults, and the causal relationship between diet and head shape was found to change as a consequence of controlled feeding. Embryonic, larval, and juvenile morphological variation and phenotypic plasticity observed in P. trucha pinpoint a possible cause for the shape variation observed in the wild. Phenotypic plasticity allows P. trucha to exploit different trophic resources and to occupy different habitats in low biodiversity lakes of Patagonia, being a major factor taking part in the past and present success of P. trucha.