They marveled at it for a few minutes, took a picture and released it. Calloway hoped to identify the species, so he sent a picture of the crayfish to his former internship supervisor, Carl Williams, who works at the Tennessee Wildlife Resources Agency.

That night, Williams recalled texting Calloway: “Did you keep it?”

Williams had also never seen a blue crayfish with orange claws, so he wanted to inspect the students’ discovery. He thought it could be a new species.

Calloway and Mathes found another blue crayfish the next day, and Williams collected a DNA sample, which he plans to mail soon to scientists at Yale University. He said that in his roughly 44-year career, this was the first time he was aware of Tennessee students potentially discovering a new species.

Mathes told The Washington Post that she never would’ve expected to check off this type of achievement in college.

“The shock really hasn’t set in for me,” Mathes said. “ … People really think this is a big deal, and me and Joe were just excited to have found something pretty.”

Calloway, 33, and Mathes, 21, are both from Tennessee and started studying wildlife at Tusculum University later than some of their peers. Calloway was a used-car dealer before studying environmental science; Mathes was on the premedical track when she discovered her passion for wildlife during an internship with the U.S. Forest Service last year.

The duo received the class assignment to study frog habitats in February and soon headed to a pond on the Greeneville, Tenn., campus’s nature trail.

State researchers have found crayfish — freshwater crustaceans that belong to the same biological group as lobsters — in a creek on the trail. But the crayfish Calloway and Mathes encountered lived underground. Plus, it differed in color from other crayfish, which typically have green, brown, orange or red bodies.

So Calloway texted Williams, a fisheries technician for the resources agency, where Calloway interned last year.

“We turned it loose to begin with, because we were like, ‘Oh, he’s just going to tell us what it is,’ ” Calloway said.

But that night, Calloway grew stressed when Williams asked whether he still had the crayfish. Calloway called Mathes, saying they needed to return to the pond to find it.

The next afternoon, Calloway and Mathes lifted rocks and leaves and studied the water for about three hours. They couldn’t find the crayfish, so they sat on a picnic table, ready to give up for the day. Then, they heard rustling.

They saw a blue crayfish climbing out of the ground on the side of a creek. They sat still for a few minutes, and when the crayfish emerged, they jumped up and grabbed it.

Calloway and Mathes put the roughly two-inch crayfish in a fish tank, which they filled with mud, leaves, sticks and insect debris to form a small habitat. They stored the tank in the school’s environmental science lab for a few days, checking on it often while they waited for a wildlife expert to examine it.

Williams visited the campus from his Morristown, Tenn., office in March. Not only were the crayfish’s colors unique, but Williams said its rostrum — an extension of the crayfish’s shell — was shorter than usual. Williams, 62, laid traps near the pond and creek in April to catch more.

Later that month, Williams cut a few of the crayfish’s legs — which the species can regenerate — for DNA samples. He placed the legs in ethanol, a compound that preserves DNA, and stored them in a refrigerator in his office while he waited to collect other specimens.

Williams said he is collecting DNA samples from other crayfish species in the state and will soon send them to Yale University for DNA extraction and analysis. He said scientists will need two to three years to determine whether the crayfish species was previously discovered. More than 90 crayfish species have been identified in Tennessee to date.

Calloway graduated from Tusculum University in May with a bachelor’s degree in environmental science and is seeking a permanent job. Mathes, a senior studying environmental science and biology, plans to share a presentation about her discovery with her classes this semester.

Both want to study animals as careers but are uncertain of their futures. However, they already have one thing they’re looking forward to: the crayfish’s DNA test results.

“It’s worth the wait to find out,” Mathes said.