The sand diver lizardfish opened its mouth to allow the goby inside to clean.

  (Mt. Irvine Extension, Tobago, British West Indies)

fish; lizardfish; sand diver; Chordata; Osteichthyes; Aulopiformes; Synodontidae; Synodus intermedius; cleaning behavior; commensal behavior;

 goby; cleaning goby; Perciformes; Gobiidae; Gobiosoma genie, Caribbean