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Long term diet differences between morphs in trophically polymorphic Percichthys trucha (Pisces: Percichthyidae) populations from the southern Andes
- LOGAN, MATTHEW S., IVERSON, SARA J., RUZZANTE, DANIEL E., WALDE, SANDRA J., MACCHI, PATRICIO J., ALONSO, MARCELO F., CUSSAC, VICTOR E.
- Biological journal of the Linnean Society 2000 v.69 no.4 pp. 599-616
- Percichthyidae, diet, digestive system, eating habits, fatty acid composition, freshwater fish, lakes, larvae, morphs, muscle tissues, natural selection, unsaturated fatty acids, Andes region, South America
- Divergent natural selection is often believed to be the driving force behind phenotypic differentiation in characters related to resource acquisition, leading to trophic polymorphism in fishes. Here we use variation in the fatty acid composition of adipose and muscle tissues to look at differences in resource use by two recently described sympatric morphs of Percichthys trucha, a common freshwater fish of the Andean and Patagonian regions of South America. Because dietary fatty acids are often stored in carnivorous animals with litde modification after consumption, they can be used to infer information about dietary habits of individuals. We found that the two morphs differed in the overall composition of fatty acids in both adipose and muscle tissue, but that there were some differences in how die morphs differed in lakes from the northern vs southern part of the range. Furthermore, we found that certain fatty acids were correlated with diet as determined by gut content analysis. Consumption of anisopteran larvae was highly correlated widi 14:0 in adipose and muscle tissue; and higher levels of longer chain unsaturated fatty acids (i.e. 20 and 22 carbons) were correlated with die presence offish and also amphipods in die diets. Taken togetiier, die results suggest that diere are marked differences in die foraging ecology of die two morphs of P. trucha inhabiting southern Andean lakes.