More than a decade after the Fukushima nuclear disaster, Japanese scientists have managed to unravel the mystery of the evolution of the hybrid pigs that roam the radioactive evacuation zone.
The story began in 2011 when domestic pigs escaped from abandoned farms after the evacuation of residents and began interbreeding with native wild boars. The result: a new generation of hybrid pigs carrying a heavy radioactive genetic legacy.
Previous tests have shown that the level of cesium-137 in some of these animals exceeded the safe limit by 300 times.
With no new pigs entering the area and almost no human activity, the area has become a natural laboratory for understanding the hybridization of domestic pigs with their wild counterparts.
This type of hybridization between domestic and wild animals is a growing concern globally, particularly in areas where wild boars increasingly interact with their domesticated counterparts, and is often associated with environmental damage. However, the biological mechanisms behind these changes remain poorly understood.
In a recent study, geneticists from Fukushima examined this rare phenomenon. The new study analyzed samples from 191 wild boars and 10 domestic pigs collected between 2015 and 2018. The team examined two types of DNA: nuclear DNA inherited from both parents, and mitochondrial DNA inherited only from the mother, allowing them to trace the maternal lineage separately.
The findings revealed that the genes of domestic pigs weaken rapidly across generations, faster than scientists had anticipated. Successive generations have become more like wild pigs than domestic pigs.
But surprisingly, despite the decline in the genetic makeup of domestic pigs, their ability to reproduce rapidly remained in hybrid pigs. Wild pigs mate only once a year, while domestic pigs reproduce year-round and in larger numbers. This trait has remained firmly established.
Scientists obtained these results by tracing mitochondrial DNA, finding that the offspring of domestic pig mothers continued to carry their genetic imprint for approximately five generations. This means that the hybrid pigs continued to interbreed with wild boars, but the rapid breeding cycle remained in place.
The team says this mechanism is not limited to Fukushima, but likely occurs in any area where there is crossbreeding between domestic and wild pigs.
