Ontogeny and plasticity of turtle feeding

Among reptiles, turtles (Chelonia) underwent great radiation, enabling them to conquer every habitat from aquatic to terrestrial, with all intermediate possibilities. The species occupying these diverse habitats are subject to the physical constraints of water or air. These properties also affect feeding. This is reflected in adaptations of the morphological and functional equipment of each species, features that should remain unchanged during ontogeny if the habitat remains constant. The proposed study will examine species which change from one environment to another during ontogeny. The project will therefore focus on whether nutrition and morphology change as well. Two species of the genus Heosemys and selected subspecies of Melanochelys trijuga will be examined, along with Trachemys scripta elegans and Glyptemys insculpta for outgroup comparison. Three ontogenetic stages (juvenile, subadult, adult) of each species will be examined. A broad range of biomechanical techniques (highspeed- and xray-cinematography, bite force measurement, standard anatomy) as well as histological, histochemical and ultrastructural methods will be applied. Combining these techniques will answer questions of function and enable a detailed examination of the morphological features necessary for feeding, with special regard to the ontogeny of the investigated species. This holistic approach, which views form and function as a unity, will provide considerable input to several key research areas: objective data for several models of vertebrate feeding, coupled with new perspectives for interpreting the evolution of this vertebrate group. Importantly, these data will be crucial for our understanding of how turtles are integrated in their particular ecosystem, eminently contributing to the conservation of this globally endangered reptile order.

Among reptiles, turtles (Chelonia) underwent great radiation, enabling them to conquer every habitat from aquatic to terrestrial, with all intermediate possibilities. The species occupying these diverse habitats are subject to the physical constraints of water or air. These properties also affect feeding. This is reflected in adaptations of the morphological and functional equipment of each species, features that should remain unchanged during ontogeny if the habitat remains constant. The proposed study will examine species which change from one environment to another during ontogeny. The project will therefore focus on whether nutrition and morphology change as well. Two species of the genus Heosemys and selected subspecies of Melanochelys trijuga will be examined, along with Trachemys scripta elegans and Glyptemys insculpta for outgroup comparison. Three ontogenetic stages (juvenile, subadult, adult) of each species will be examined. A broad range of biomechanical techniques (highspeed- and xray-cinematography, bite force measurement, standard anatomy) as well as histological, histochemical and ultrastructural methods will be applied. Combining these techniques will answer questions of function and enable a detailed examination of the morphological features necessary for feeding, with special regard to the ontogeny of the investigated species. This holistic approach, which views form and function as a unity, will provide considerable input to several key research areas: objective data for several models of vertebrate feeding, coupled with new perspectives for interpreting the evolution of this vertebrate group. Importantly, these data will be crucial for our understanding of how turtles are integrated in their particular ecosystem, eminently contributing to the conservation of this globally endangered reptile order.