A recent study has explored the genetic basis of gut length variation in cichlid fish species, revealing that some genetic loci are sex-specific despite males and females having similar gut lengths. This research supports the idea of “sexual conflict,” where evolutionary pressures differ between sexes, potentially affecting gut length evolution.
Reade Roberts, an associate professor at North Carolina State University and corresponding author of the study, explains, “Gut length is an incredibly important trait for animals, and there are consistent trends across different groups of animals where carnivores tend to have short guts, and herbivores tend to have long guts.” However, he notes that little is known about the genetic basis of these differences due to challenges in genetic mapping studies.
The study involved two closely related cichlid species from Lake Malawi in central Africa—one omnivore and one carnivore—that diverged around a million years ago. Researchers compared these species with a hybrid population to identify genetic loci associated with gut length. They found loci impacting both sexes equally but also discovered sex-specific effects across species.
Roberts highlights the complexity by stating, “The question now is why is there a genetic variant only active in females or males.” The differing dietary pressures faced by male and female cichlids could be a factor. Males are territorial with varying food availability while females range more widely but experience starvation periods when holding offspring in their mouths.
“It could be dietary pressure, it could be hormonal – we don’t know,” Roberts adds. He emphasizes that considering sex was crucial for identifying most loci related to gut length.
This research may also inform human health studies. “The basic questions – how did these differences arise and what do they mean for health outcomes – will lead to a better understanding of genetic pathways,” says Roberts.
Published in Genetics on May 26th, this work received support from several organizations including the Arnold and Mabel Beckman Foundation Young Investigator Award; National Science Foundation; U.S. Department of Agriculture; and National Institutes of Health. Aldo Baez from NC State is noted as the first author.
