Facultative cleaning behavior in a western Atlantic sponge goby, Elacatinus xanthiprora (Teleostei: Gobiidae)

There are two large sets of brightly striped gobies of the genus Elacatinus in the warm waters of the western Atlantic Ocean: one that cleans larger fishes at cleaning stations on coral reefs and another set that live in and among sponges and are not known to clean. The two sets of gobies are phylogenetically separate as well, forming two independent monophyletic sets of mtDNA-sequence lineages. At almost all locations there are species of both groups present; however, at the northern temperate limits, along the northern coast of the Gulf of Mexico and along the east coast of the USA at North Carolina (beyond the range of coral reef development), only one species is present and it belongs to the sponge goby group. We report here that the Yellowprow Goby, Elacatinus xanthiprora, a member of the sponge goby group, regularly cleans fishes, both in the northern Gulf of Mexico and off North Carolina. Apparently, the absence of a local cleaner species permits the evolution of facultative cleaning behavior in a species from a group characterized by the absence of that behavior