A recent study has revealed that a single gene regulating testosterone levels in a unique species of shore bird influences the development of three distinctly different male types. Ruffs, the focus of this research, have intrigued scientists due to their three male morphs, which showcase striking differences in both appearance and mating behaviors.
A recently conducted international study, which included researchers from Simon Fraser University, has determined that a single gene that manages testosterone levels in a particularly unique species of shore bird plays a key role in the formation of three very different male types.
Scientists have long been captivated by ruffs, which exhibit three male morphs that are vastly different from one another in both looks and mating practices.
A new article published in the journal Science this month has revealed that these morphs arise from a powerful enzyme (HSD17B2) found in the birds’ blood, capable of managing testosterone levels and quickly breaking down this hormone that is typically linked to male dominance and aggression.
“The species is fascinating, featuring three types of males that look and behave in remarkable ways,” states David Lank, a biologist at SFU who has dedicated 40 years to studying ruffs and was part of the team that first discovered variations in testosterone levels among the morphs. “This research provides significant insights into the genetic and physiological processes that govern the emergence of these male types.”
The majority of male ruffs are classified as “independents,” recognized for their impressive darker breeding feathers and their aggressive claims over small territories to attract females, who are solely responsible for parental duties. On the other hand, “satellites” are smaller males with lighter plumage who form partnerships with independents to display together for females. Although they cooperate to some degree, each male still aims to mate with as many females as possible.
The third type, known as “faeders,” adopts a clever strategy by completely forgoing display behavior and distinctive plumage, allowing them to impersonate females and sneak into mating areas without attracting attention.
For both satellites and faeders, whose mating strategies do not involve aggressive behavior, excess testosterone is detrimental. Previous research has indicated that these two male types have significantly lower levels of testosterone in their blood.
The new study pinpointed the specific gene responsible for producing the enzyme that regulates testosterone throughout the body, excluding the testes, where testosterone remains essential for generating competitive sperm.
Lank notes that ruffs are remarkable due to having three male morphs and exhibiting chromosomal inversions; however, the hormonal mechanisms discovered apply broadly across all vertebrates, including humans.
He also mentions that a special variant of the steroid hormone gene identified in this research could potentially have future therapeutic applications for humans, although more research is necessary.
“HSD17B2 is three to four times more effective at converting testosterone into androstenedione,” he explains. “This raises possibilities for treating individuals with certain hyper-testosterone conditions using this version of the enzyme or a synthetic enzyme modeled after its structure.”
This study was conducted by researchers at the Max Planck Institute for Biological Intelligence in Germany, in collaboration with scientists from SFU, FU Berlin, the University of Vienna, and Helmholtz Munich.
