Kalmar "Genus Uca" tana nufin jinsin kaguwa da aka fi sani da fiddler crabs. Wannan jinsin na dangin Ocypodidae ne kuma ya haɗa da nau'ikan kanana sama da 100, ƙananan kaguwar ƙasa waɗanda ake samu a yankuna masu tsaka-tsaki tare da gaɓar teku a duniya. Waɗannan kaguwar suna da siffa ta musamman ta ƙwanƙolin asymmetric, tare da katsa ɗaya ya fi ɗayan girma. Ana amfani da mafi girman farantin don sadarwa, jawo hankalin abokan aure, da kuma don tsaro.