Date of Award

Spring 5-7-2016

Degree Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Matthew Grober

Second Advisor

Dr. Aaron Roseberry

Third Advisor

Dr. Walter Walthall


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 develop into mini-nesting males in a laboratory setting. We tested whether or not some of the small males in the wild are actually mini-nesting males by comparing the content of the accessory gonadal structure (AGS), a prostate-like gland that is known to have different functions in nesting and mini-males. Over half of the mini-males had AGS contents typical of nesting males as well as larger dorsal fins and longer genital papillae than the alternative males. These findings add to our understanding of the role of the environment in regulating sexual phenotype in L. dalli.