Ant Reproduction: Ancient Genetic Components Determine Sex Of Offspring

Throughout the animal kingdom gender is largely based on genetic information passed down by mom and dad. The Y chromosome triggers male development in humans, for instance, but that doesn't seem to be the case for ants, wasps and bees, according to researchers from the Okinawa Institute of Science and Technology Graduate University (OIST). 

For ants, sex is determined by a system called haplodiploidy, in which a mechanism known as complementary sex determination controls genetic recombination. While females are diploid, meaning they have two complementary versions of sex-determining genes – one set inherited from the mother and another from the father – males, on the other hand, are haploid, which means they have only a single version of these genes, according to a news release. It follows then that inbreeding produces sterile diploid males since close family members are likely to share the same genetic variants. This creates a problem for male ants since their primary responsibility is reproduction; females preform other work-related functions.

In an attempt to better understand which genes are involved in complementary sex determination, the OIST team of researchers analyzed a species of ants from Japan known as Vollenhovia emeryi. For their study, genetic crosses were conducted between brothers and sisters in order to induce the production of sterile males. This allowed them to narrow down which genomic regions are associated with complementary sex determination.

So what did they find? In the case of Vollenhovia emeryi, researchers discovered two separate genetic sex determination regions cause 25 percent of inbreed males to become sterile. While one of the sex determination regions has been passed down through ant lineages for more than 100 million years and is also involved in honeybee sex determination, the other region is new to science and requires further study. 

"Sex determination systems are believed to evolve rapidly, but these data suggest that elements of the sex determination system used by bees and ants actually date to the time of the dinosaurs. These findings also show that there is still much more to learn about the molecular diversity of sex determination mechanisms," Professor Alexander S. Mikheyev, leader of the study from the university's Ecology and Evolution Unit, explained.

Their study was recently published in the journal PLOS Genetics.

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