Non-additive dietary interactions between plant and animal material in juvenile slider turtles, Trachemys scripta.
Bouchard, Sarah*,1, 1 Otterbein College, Westerville, OH
ABSTRACT- Non-additive dietary interactions occur when energy and nutrient gains from a mixed diet are greater than or less than that predicted by summing the gains from individual diet items. Both positive and negative interactions have been documented in a wide variety of species, including adult slider turtles, Trachemys scripta. Such non-additive interactions may be critical to the nutritional ecology of juvenile T. scripta, because, like many turtle species, they experience an ontogenetic diet shift from carnivory to herbivory. During this transition, they consume varying ratios of plant to animal material. The purpose of this study was to determine if juveniles experience non-additive effects similar to those found in adults and if these effects are related to differences in diet transit time as has been suggested. Fifty juvenile turtles were maintained on one of five diets for six weeks: 100% duckweed, Lemna minor, 100% cricket, Acheta domesticus, or one of three mixed diets containing 33.8% duckweed and 66.2% cricket, 60.6% duckweed and 39.4% cricket, and 79.1% duckweed and 20.9% cricket. Turtle growth rates were measured on these diets, as well as diet transit times. A non-additive effect was demonstrated in growth on the 79.1% duckweed diet, but not on the other mixed diets. Transit times varied significantly between the plant and animal diets and may contribute to the observed effect. Quantifying these effects on juvenile nutrition is important to our understanding of turtle ecology because juvenile growth rates are linked to survivorship and future reproductive success.
Key words: non-additive diet effects, Trachemys scripta, physiological ecology
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