Researcher(s)
- Caitlin Bailey, Marine Science, University of Delaware
Faculty Mentor(s)
- Jennifer Wyffels, Center for Bioinformatics & Computational Biology, University of Delaware
Abstract
Several species of shark exhibit tooth morphology changes throughout their lifespan that may reflect changes in diet as they grow. Sand tiger shark (Carcharias taurus) tooth morphology has not been examined throughout its lifespan despite a rare requirement for teeth during embryonic development. Sand tiger sharks are viviparous but not placental and use a reproductive mode termed adelphophagy. In this reproductive mode, developing embryos use precocious dentition to break out of their egg case to seek out and kill other developing embryos. Females have paired uteri and ovulate eggs for the first half of gestation as a source of nutrition for the surviving embryo in each uterus. Gestation lasts approximately ten months and when born, neonates are nearly a meter in length, half the size of the female.
Sand tiger neonates must hunt for prey on their own after parturition because there is no parental care for sharks. Changes in prey that occur as sharks grow and mature may be reflected by changes in tooth shape. To better understand how tooth shape relates to prey for sand tiger sharks, teeth from various life stages were imaged using microtomography (micro-CT) and reconstructed in 3D using NRecon, DataViewer, and Amira. Once reconstructed, a suite of morphological measurements were collected for each tooth and compared across adult, juvenile, and neonatal teeth. One of the most obvious changes is the presence of lateral cusplets which first appear in juvenile specimens and are retained in adult teeth. These findings contribute to a deeper understanding of tooth development and reproductive adaptations of sand tiger sharks.