These four images show the sequence of tadpole vortex formation in Mexican Spadefoot toad tadpoles, Spea multiplicata.
Vortices form when tadpole density reaches a critical threshold. The flow generated causes detritus matter at the bottom of ponds to be disturbed, facilitating feeding. Therefore the mechanisms leading to the formation of the vortex structure could be a collective foraging strategy.
Initially, individual tadpoles are orientated randomly in space (first panel), but after the detection of food, tadpoles begin to aggregate (second panel). The tadpoles beat their tails quickly and swim into the current generated by others (third panel) until a vortex is fully formed (fourth panel).