Genome of World's Largest Shark to Be Sequenced
The whale shark's mouth can be up to 5 feet (1.5 m) wide, lots of room for scooping up ocean snacks.
Credit: Mote Marine Laboratory

The whale shark is a creature of many mysteries. Now, researchers hope to answer a few by sequencing the complete genome of the world's largest fish.

Researchers at Emory University and the Georgia Aquarium are working to create a complete library of whale shark DNA, sequencing the genomes of the aquarium's captive sharks, which come from Taiwan, and comparing them with wild whale sharks in Mexico

"Mapping the genome is like an encyclopedia of life — it gives scientists the ability to ask questions," study leader Tim Read of Emory said in a statement. "In the architecture of the genome, it's a bit like archeology. We can see the history of the whale shark in its tissue."

The genome sequencing project will take months to complete, but when it's done, researchers hope it will help them answer questions about the whale sharks' little-understood lifestyle. No one knows, for example, what genes are responsible for the whale shark's enormous size, which can top out at 40 feet (12 meters) long. The study may also help researchers understand where the giant filter feeders fit into the entire family of sharks, according to the Georgia Aquarium. 

In addition to sequencing the animal's genome, other groups of scientists hope to study some odd behaviors to find answers to whale-shark questions. An odd feeding frenzy in the waters off the Yucatan Peninsula has long puzzled marine scientists. Every year for the past few years, the blue, plankton-rich waters have become an all-you-can-eat haven for hundreds of giant whale sharks, an annual event known as "afuera."

Observations there have already shed light on the sharks' eating habits: The afuera occurs where a type of tuna called the little tunny spawns. The whale sharks scoop up the eggs that rise to the water's surface, researchers say.

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