A cleaning interaction between sailfin mollies ( Poecilia latipinna ) and humans in Lake Vouliagmeni, Greece

Here, I report an unexpected interaction between the introduced fish species, Poecilia ( Mollienesia ) latipinna and humans in Lake Vouliagmeni, Greece. In this lake, I observed the normally skittish P. latipinna approach and graze on the exposed skin of bathing humans, presumably removing dead skin cells in what amounts to an exfoliating process. The natural occurrence of this phenomenon in Lake Vouliagmeni is likely a product of multiple contingencies, including the introduction of P. latipinna sometime around the mid-twentieth century, and the fairly unique ecological circumstances. I suggest and discuss several conditions that must be met for such a cleaning interaction to develop, including an appropriate fish species being present, an environment in which fish are able to safely approach humans without being captured or otherwise harmed, and human tolerance—even enjoyment—of the behavior. Finally, I point out a number of remaining questions including whether both species receive a net benefit, if there has been any behavioral or physiological feeding specialization, and whether similar phenomena occur elsewhere in the world.