Figure 37.9: Investigating the Mechanism of Sex Change In contrast to the anemonefish, females of the blackeye goby (Coryphopterus nicholsii) sometimes become males. Investigators have been studying the mechanism by which this occurs. By simply describing blood hormones, the investigators have found that the female-to-male transition is accompanied by a decline in the blood concentration of the female sex steroid 17β-estradiol and an increase in the concentration of the male sex steroid 11-ketotestosterone (11-KT). But do these changes in hormones cause the sex change? Are they sufficient to make a female change into a male? To find out, the investigators artificially manipulated the hormone levels.a