The hunt for Crawzilla
It all started with a bit of friendly office banter. Caitlin Bloomer, a teaching assistant professor at the University of Illinois Urbana-Champaign, found a massive crayfish in a Kentucky mud puddle. She dubbed it “Crawzilla” and was convinced she had snagged the biggest one ever. When she brought her trophy to a colleague, he wasn't having it. Real talk: he claimed he’d caught much bigger ones himself.
That disagreement turned into a nationwide search. Bloomer teamed up with researchers across the country to measure preserved crayfish specimens from museum collections using high-precision calipers. The team analyzed 20 of the largest specimens representing 18 different species to see who really held the crown.
The record-holder
So, did Crawzilla win? Not quite. While Bloomer's find made the top 20 list—and was notably the only burrowing crayfish to qualify—the top spot went to a Tennessee bottlebrush crayfish from a collection at West Liberty University in West Virginia. This absolute unit of a crawdad was collected way back in 2011 by Dr. Zac Loughman and his students. It measured about 3.4 inches (86.6 millimeters) just for its body, excluding the tail and claws. Its carapace alone is roughly the size of a credit card. It’s giving main character energy.
The big biological question
Beyond the competition, the data revealed something wild: North American crayfish seem to max out at around 80 millimeters. This is a total mystery because, in other parts of the world, crayfish like the Tasmanian giant freshwater crayfish can grow way bigger.
The researchers looked for reasons—like oxygen levels, geography, or habitat—that might explain why North American species stop growing when they do. They didn’t find any clear patterns. The current theory? It might come down to their own biology, like their exoskeleton structure or muscle anatomy, acting as a physical limit. It’s a hypothesis for now, but scientists are stoked to dive into the physiology to see if their shells are holding them back.
Why it matters
We’ve all caught crawfish in a creek as kids, but it’s honestly wild how much we still don’t know about them. This study proves that museum collections are lowkey gold mines for science, allowing researchers to study history that’s already sitting on a shelf. The team is now planning to dig deeper into why these creatures hit their growth ceiling, proving that even the most common backyard critters still have secrets left to tell.
