Scientists find genetic conflict between mothers and babies in fish

Evolutionary biologists at the University of California - Riverside identified a genetic conflict between mothers and their developing offspring in a species of fish with a placenta.

David Reznick and his team discovered that these fish exhibit genomic imprinting, a process where only one parent's copy of a gene remains active while the other is silenced. This finding suggests that the biological struggle over nutrient distribution during pregnancy exists outside of mammals.

The researchers believe this conflict arises because mothers and developing babies have competing evolutionary interests. A baby benefits from taking as many nutrients as possible to ensure its own survival. However, a mother must conserve enough energy and nutrients to survive and produce additional offspring in the future. Because a baby only shares half its genes with a sibling, the genes inherited from the father may favor the baby's immediate growth, while the mother's genes favor her long-term reproductive success.

To test this, Reznick bred fish family lines through 10 to 12 generations of brother-sister matings before crossing them to distinguish maternal and paternal genes. Collaborators at the Auburn University College of Veterinary Medicine analyzed the placental tissue and found patterns where one parent's genes were more active than the other's. These results indicate that fish and mammals independently evolved similar biological solutions to manage these competing demands over millions of years.