Testing for the Existence of Small Nesting Males in a Natural Population of Bluebanded Gobies, Lythrypnus Dalli.

Joseph Bush


In protogynous fishes, smaller individuals tend to be female and only the largest individuals are male. In Lythrypnus dalli the small population of mini-males that are found in the wild are typically alternative males that mimic females to gain access to the nest. However, recent work has shown that small juveniles can become mini-nesting males in a laboratory setting. We tested whether or not some of the small males in the wild are actually juvenile nesting males by comparing the content of the accessory gonadal structure (AGS), dorsal fin morphology, and genital papilla structure of 11 small males sampled from a natural population. Over half of the mini-males had AGS contents typical of nesting males as well as larger dorsal fins and larger genital papilla than the alternative males. These findings add to our understanding of the role of the environment in regulating sexual phenotype in L. dalli.