Attachment and Release of Water Fleas' Ephippia on a Medium-Sized Waterfowl's Leg for Migration

Planktonic crustaceans of the genus Daphnia live in aquatic environments. Although they lack walking and flying capabilities, they have developed adaptations that facilitate the dispersal of their dormant forms, ephippia, to cross terrestrial barriers and reach neighborhood water bodies. It increases the survival rate of their species. It is reported that one of the ways this spread occurs is the transport of their ephippia through waterfowls' legs. Yet, little is known about how these ephippia are initially attached to the waterfowls' legs. In this work, using the legs of American Pekin ducks as test samples, we found that a "coating" mechanism might play a significant role in this attachment and that surface tension-induced attraction might have a secondary effect on it. Furthermore, we demonstrated that, no matter whether a duck's leg was inserted into water at a high or low speed, an ephippium could be released from the leg.