Exploring tadpole swimming strategies and dynamics

Tadpoles are some of the simplest swimming animals, capable of fast and agile movement with little more than a head and a tail. These creatures could serve as a template for robotic microswimmers, but first, it is important to understand the mechanics of tadpole motion and recreate that motion numerically.

Jiang et al. constructed a numerical model of a free-swimming tadpole using the immersed boundary-lattice Boltzmann method (IB-LBM). Their model explores the efficiency of multiple swimming behaviors inside a narrow channel.

“The IB-LBM is good at dealing with complex motion boundaries and fluid-structure coupling problems,” said author Yuan-Qing Xu. “In a specific fluid, we use periodic forces to generate tail oscillation, so that the tail movement is flexible, and the tadpole can swim freely.”

The authors based their model on the tadpole form of the dark-spotted frog, a common species in the Korean peninsula. A lattice structure forms the body and tail of the model, which is controlled by varying the angle and amplitude of the tail swing.

Using this model, the researchers found that a narrower swimming channel results in a slower swimming speed, while speeds too fast or too slow lead to instability. They incorporated a simple perception-response strategy for directional movement and demonstrated the tadpole’s ability to navigate obstacles and follow a path.

“Our next plan is to develop the group swimmer model and discover the mechanism of collaborative swimming,” said Xu. “The long-term goal is to update this model to 3D and develop experimental devices, applying them in performing desired underwater tasks.”

Source: “A free-swimming tadpole model based on immersed boundary-lattice Boltzmann method and its application,” by Si-Ying Jiang, Jun Yu, Jun Wang, Dong-Fang Li, and Yuan-Qing Xu, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0161749 .