Flotation of Aquatic Worms

The California blackworm L. variegatus generally lives underwater but it can extend its posterior end to the water surface to breathe. Little is known about the flotation forces it achieves through this process. In this experimental study, we visualize the meniscus shape for blackworms and cylindrical rods and compare them to theoretical predictions from Vella, Lee and Kim (2006). We measure the Bond number and specific gravity for blackworms, leeches, and other common invertebrates that inhabit the water surface. Using this theoretical framework, we calculate the factor of safety for flotation of blackworms and other organisms.