桃瘾社区

The growing invasion of Brazilian pepper trees in Tampa Bay is distressing native crabs to the point of cannibalism more than ever before.

That鈥檚 the hypothesis of Jessie Wahlers 鈥�25, a marine biology major studying Aratus pisonii, also known as the mangrove tree crab, a keystone species and a vital part of Florida鈥檚 natural ecosystem.

鈥淭hey're one of the major connections between the water and the air when it comes to mangrove communities,鈥� Wahlers said. 鈥淭hey contribute to so many different little things that add up to 鈥楬ey! Really important!鈥欌��

So when Wahlers learned from biology Assistant Teaching Professor Kristian Taylor that the shiny, black, tree-clinging creatures were chowing down on their own in greater numbers, she wanted to know why. She found four scholarly articles that mentioned the species鈥� cannibalism, but none explored why the behavior appears to be getting more prevalent.

鈥淲e did the preliminary research,鈥� she said, and 鈥渋t was like, 鈥極h yeah, by the way, I saw a couple eat each other.鈥�

鈥淚t was an afterthought.鈥�

According to the National Park Service, the Brazilian peppertree first invaded Florida in the middle of the 19th century, imported for use as Christmas decorations. Now they鈥檙e here all year.

Wahlers had a hunch about the crabs鈥� behavior and their changing habitat. So after securing the necessary permissions, she went to work.

She collected 45 crabs from Tampa Bay鈥檚 Gandy Beach, Picnic Island and Cypress Point Park and distributed them evenly into three GoPro-equipped, habitat-mimicking tanks set up in a campus lab: one full of invasive peppertree, one with native mangroves and one with both.

Wahlers first measured the crabs, determined their genders and numbered their backs with an oil-based Sharpie. She handled the crabs carefully.

鈥淭he larger ones (20-25 millimeters across), those guys got claws,鈥� she said. 鈥淚 found you have to grab them right at the edge where their abdomen and their top meet. Normally, I have longer nails 鈥� I found that helps because it's like a shield,鈥� Wahlers said.

She鈥檇 also put sticks in their claws to keep them occupied.

She monitored the tanks and the resident crabs for 10 weeks and recorded her work.

Each Saturday, Wahler took a crab census. Then, survival of the fittest played out over the ensuing days. She took each week鈥檚 survivors back to the bay before restarting the cycle.

She noticed the attacks on each other seemed to be motivated by size 鈥� and more crabs perished in the peppertree-only tank. Sometimes, up to half of them would have been cannibalized.

鈥淚t's definitely causing more deaths. 鈥� It could be the nutrient difference, that there鈥檚 something with the nitrogen or carbon in the Brazilian peppertree leaves.鈥�

Wahlers doesn鈥檛 want her research to stop at a science paper.

鈥淚鈥檇 love to turn this into an awareness campaign,鈥� Wahlers said. 鈥淓specially for Florida, one of the big issues is native plants versus invasive. It's messing with things 鈥� Come on!鈥�