Cannibal Tadpoles Aid in Understanding Digestive Evolution

A genetic study of two types of frog tadpoles - a cannibalistic carnivore and a humble algae eater - may play a role in furthering our understanding of the evolution and development of digestive organs, according to researchers at North Carolina State University.

The research focused on tadpoles of the African clawed frog, an algae-eating tadpole, and Budgett's frog, an aggressive species of frog which is carnivorous - and cannibalistic - in the tadpole stage. (See Photo.) 

The African clawed frog's long digestive tract in unable to process protein until they become adult frogs. As well as a different diet, the tadpoles last shared a common ancestor about 110 million years ago, the researchers report.

Based on a prior understanding that some tadpoles have evolved shorter guts to digest protein much earlier in the development stage, Nascone-Yoder exposed African clawed frog embryos to a compound that inactivated a variety of genes to see if the clawed frogs would develop a more carnivore-like digestive tract.

And indeed, the molecule compound she applied to the embryos caused the African clawed frog embryos to develop guts similar to the carnivorous Budgett's tadpoles. 

In a strange biological twist, Nascone-Yoder also found that if she applied a molecule compound with the opposite effects as the first compound to Budgett's frogs and found that they developed guts similar to the African clawed frog.

"Essentially, these molecules are allowing us to tease apart the processes that play a key role in gut development," Nascone-Yoder said in a statement. "Understanding how and why the gut develops different shapes and lengths to adapt to different diets and environments during evolution gives us insight into what types of processes can be altered in the context of human birth defects, another scenario in which the gut also changes its shape and function."

These findings may also shed light on universal rules of organ development that could lead to better diagnosis and prevention of intestinal birth defects.

The research appears in the journal Evolution and Development.