A giant crayfish discovered in Kentucky prompted an investigation into the upper size limits of North American crayfish. Caitlin Bloomer, a teaching assistant professor at the University of Illinois Urbana-Champaign, initially believed her catch was the largest ever documented. When a colleague challenged that claim, she contacted biologists and museum curators nationwide. Using precision measuring instruments called calipers, researchers compiled a list of 20 exceptionally large specimens representing 18 species. Bloomer's catch qualified and was the only burrowing crayfish included. The findings appeared in the journal Ecology.
The record-holder was a Tennessee bottlebrush crayfish preserved at West Liberty University in West Virginia. Collected in 2011 by Dr Zac Loughman and university students, it had a main body measuring 86.6 millimetres, excluding its tail, claws and antennae. Despite differences between species and environments, the largest specimens generally approached 80 millimetres in the measurement used. That apparent ceiling contrasts with the much greater size attained by crayfish elsewhere, including the Tasmanian giant freshwater crayfish.
Neither geographical location, oxygen availability nor habitat type showed a clear relationship with maximum body size. The researchers therefore proposed that biological characteristics, rather than environmental conditions alone, might constrain growth. Differences in exoskeleton structure or muscle anatomy are possible explanations, although further investigation is required to test them. Beyond identifying unusually large animals, the project demonstrated how preserved museum collections can support research into fundamental biological questions.
