Meeting Abstract
All turtles have a higher mortality risk as juveniles due to their smaller, less ossified, and weaker shells. Thus juveniles must use other strategies such as concealment or escape to avoid predation. Previous research has hinted that juvenile aquatic turtles hatch with relatively hydrodynamic shells, and only develop stronger shapes as they grow. However, these ideas have never been examined across multiple species. We collected data from 8 emydid species, both terrestrial and aquatic. 3D landmark data was used to analyze the relationship between shell shape and size. We predicted that juvenile’s shells in aquatic, but not terrestrial, species will be more streamlined than adults. Relationships between size and shape, species and shape, and their interactions were significant. Juvenile turtles have more circular shells in dorsal view, with flatter carapaces and greater distances between carapace and plastron; shells become more ovate and domed with growth. These changes are consistent with decreased hydrodynamic efficiency, as predicted. However, in contrast to predictions, terrestrial turtles share these same general trends. Box turtles show the strongest deviation from this pattern, most likely due to their hinged shells. We find strong consistency of patterns of shell growth, independent of habitat, perhaps indicating a lack of time for early developmental changes to accumulate in terrestrial lineages, lack of selective pressure for changes in hatchling shell shape, or constraints imposed by the need to fit inside an egg during development. By understanding juvenile turtle shell ontogeny, conservation efforts can be developed to protect turtles in their most vulnerable stage.
