Inside Leatherback Turtle Mouth: What Is the Use of Its Backward-Pointing Teeth?

A leatherback turtle (Dermochelys coriacea) is the largest living turtle and the heaviest non-crocodilian reptile, measuring up to 5.9 feet (1.8 meters) and weighing 1,100 pounds (500 kg). Such a huge body requires a steady diet consisting of soft-bodied invertebrates like jellyfish and tunicates. To help retain and swallow their gelatinous prey, a leatherback's mouth and throat contain hundreds of backward-pointing spikes which look like tunnels of sinister spines.

Structure of Leatherback Turtle Mouth

The spikes found inside the mouth of a leatherback turtle are called papillae. Although they look very sharp, these are not considered as teeth. The vicious spines are not intended to intimidate their prey or to rip them to pieces. Instead, the spikes are used to stop the turtle from releasing all its food.

The primary purpose of the spike is to move the food from the mouth through its digestive system, with the thresher-like tract extending through its unusually long esophagus, past its stomach, and to its rear. It loops back and connects to the stomach like a conveyor belt which catches, stores, and continuously processes food. As described by biologist Helen Kairo, the pointed spines act as anti-vomiting spikes.

Land turtles do not have this set of spines in their throat because they use esophageal muscles to move their food just like humans do. However, sea turtles do not have the privilege of swallowing food on dry land. The leatherback turtle swallows a lot of seawater while eating, making their stomach filled up with food and water. As they vomit out all the water, the food must be trapped and kept from coming out. Therefore, the spikes serve as a kind of reverse filter.

Aside from it, the sharp spikes also protect the sea turtle from dangerous prey. Since jellyfish is the leatherback turtle's favorite food, it is just practical that its body is protected from stings. The backward-facing papillae also prevents the slippery jellyfish from escaping by floating out of the turtle's mouth.

Major Population Threat

Plastic ocean pollution has recently been recognized as having a dangerous effect on leatherback turtles. A 2015 study conducted at the University of Queensland revealed that 52% of the turtles of the world have eaten plastic waste.

Despite the turtle's brilliantly designed digestive system, the turtle is still unable to distinguish between jellyfish and plastic trash that floats on water. For a leatherback turtle, a floating plastic bag resembles a jellyfish, algae, or other species that make up a large part of its diet. Once the poor creature swallows a piece of plastic, the spikes in its mouth make it hard for the turtle to get rid of them.

Leatherback turtles currently face the threat of extinction. In 2013, it was assessed for The IUCN Red List of Threatened Species and was listed as vulnerable. Their population has decreased over the past 20 years as humans collect their eggs for consumption. They also frequently get caught in fishing gears which are intended for other marine animals.

Check out more news and information on Sea Turtle in Science Times.