Research

I am interested in neuroendocrinology, physiology, behavioral biology, biotechnology, and genetics. Broadly speaking, my graduate studies focus on how the brain integrates and converts social information into reproductive responses.

Under the advisement of Dr. John Godwin, I am researching the potential involvement of the hypothalamic kisspeptin system in socially-induced sex change in a coral reef fish, as well as the kisspeptin system’s potential interaction with other neuropeptide systems in the brain to promote sex change. Kisspeptin is produced in the brains of other vertebrates as well, including mammals, amphibians, and reptiles. Kisspeptin helps to initiate puberty and maintain reproductive function during adulthood. I am testing whether kisspeptin also plays a role in sex change in sex-changing fishes.

For this research, I study the bluehead wrasse (Thalassoma bifasciatum), a diandric (two male phenotypes) protogynous (female-to-male) sex-changing coral reef fish from the Caribbean. Females and initial phase (IP) sneaker males are capable of undergoing sex change and role change, respectively, to become terminal phase (TP) males.

A territorial TP male. Photo courtesy of John Godwin and Bill Tyler.

A territorial TP male

A gravid female. Photo courtesy of John Godwin and Bill Tyler.

A gravid female

An IP male or female and a non-territorial TP male. Photo courtesy of John Godwin and Bill Tyler.

An IP male or female and a non-territorial TP male on the edge of the reef

There is a strong drive for females and IP males to become TP males to increase their reproductive success. The dominant, aggressive TP males court and spawn with females, and can spawn multiple times a day. The most prolific TP males can spawn over 100 times in a 2-3 hour spawning period! By contrast, females spawn once during the daily spawning period (two out of every three days, on average). IP males resort to group spawning with females on larger reefs in groups of 5-20 IP males to one female, or IP males may try to sneak in on a pair spawn between a female and TP male.

We can induce sex change in females on patch reefs by removing TP males

The largest females can undergo behavioral sex change within minutes to hours after removing TP males. In some cases, behavioral sex change takes longer to appear. The ovaries begin to break down a couple days into sex change, testis tissue starts to appear as early as 4-5 days, by 8-10 days the testes produce mature sperm, and by 3 weeks the sex-changed female has the complete TP male coloration.

A female, sex changer, and TP male.

A female, sex changer, and TP male.

Females typically show changes in behavior (increased aggression, courtship, and other TP male-typical behaviors) before the gonads change from ovaries to testes. We are testing whether vasotocin, a neuropeptide necessary for behavioral changes, communicates with neuropeptide systems that may be controlling gonadal changes, such as kisspeptin.