Scaling of Dentition and Prey Size in the California Moray (Gymnothorax mordax)
Physical and Biological Sciences
Mehta Lab
Teeth are a great way for scientists to obtain a general understanding of an animal’s diet. Long pointy teeth are good for piercing, while hard flat teeth are ideal for crushing prey. Organisms can also drastically change the shape of their teeth as they grow. By changing tooth shape over time, organisms can vary their diet and take advantage of new resources. For example, when the American Alligator is a juvenile, it uses its needle-like teeth to capture and kill fish and insects; over ontogeny, the teeth become thicker and blunt so that the alligator can crush the shells of large turtles and the bones of large mammals. Smaller vertebrates such as black water fishes, found in the Amazon Basin, consume microcrustaceans and insects when they are young and transition to eating scales when they are adults. This transition to scale eating is accompanied by a transformation from small needle-like teeth to more specialized larger and rounder teeth. To document the relationship between teeth and long-term dietary strategies, multiple individuals over a large range of sizes are usually sampled. With a size range of individuals, we can measure dentition as it relates to body size, and if possible compare those patterns with stomach contents or other dietary data.
For my project I wanted to investigate whether tooth morphology and diet changed over time in the California moray eel, Gymnothorax mordax. My collaborators and I designed a project where I could measure the dentition of specimens collected from the field and compare these data to the stomach contents of wild individuals . I took measurements for 1,364 teeth spread across 21 moray eels. These eels ranged in size from 383 – 1110 mm total length. I compared the length and width of teeth relative to body size to determine the scaling patterns of dentition over time. I also examined whether the aspect ratio of teeth (length x width) changed over ontogeny. I then paired these data with diet data from a wild populations of morays. I was able to gather prey from the stomachs of 45 individuals with a comparable range in size to my preserved specimens. The results of my analysis show that tooth length and width in the California moray maintain the same shape and grow in proportion to the eel. The data from stomach contents show that over ontogeny, morays eat larger fish prey; however, they still retain small fish prey items in their diet. This means that as morays grow, they expand their diet to include large and small fish prey rather than specializing on a particular prey size. Together, the tooth patterns and dietary data suggests that the California moray does not undergo an ontogenetic shift in prey size over ontogeny.
