Observations on the Burrow Structures and Larval Behavior of Ephoron shigae (Takahashi, 1924) (Ephemeroptera: Polymitarcyidae) in River Sediments

The larvae of the mayfly Ephoron shigae (Takahashi, 1924) (Ephemeroptera: Polymitarcyidae) inhabit distinctive U‐shaped burrows in river and lake sediments, yet their ecology remains poorly documented. Using newly developed mechatronic technology, we obtained continuous observations that revealed new aspects of larval behavior. The larvae first construct a U‐shaped burrow and then extend it by adding an additional channel without leaving the original structure. This channel branches from the deepest point of the burrow and faces upstream, opposite the river current. Our fluid‐engineering analysis indicates that constructing this branch at an acute angle enhances the inflow of detritus and oxygen, the larvae's primary resources. As bioirrigators, E. shigae larvae may use this upstream‐facing channel to enhance oxygen supply within the burrow, particularly when oxygen levels decline due to the respiration of larvae and microorganisms. Robotic and artificial water‐channel systems now enable automated observation of burrowing mayflies like E. shigae in bottom sediments.