Phenotypic plasticity in female naked mole-rats after removal from reproductive suppression

Abstract

Naked mole-rats are fossorial African rodents that live in large, eusocial groups. Adult subordinate female mole-rats are reproductively suppressed by the dominant breeding female in their colonies. As a result, subordinate females remain reproductively quiescent for their entire lives unless they are removed from the suppressive presence of the dominant female. This makes subordinate female mole-rats a tractable model for studying phenotypic plasticity. We measured skeletal growth of subordinate, suppressed females as they changed reproductive status. After housing subordinate female mole-rats separately from their home colonies, these animals experienced a growth surge that dramatically increased their body mass and length. After removal from reproductive suppression, females showed an 82% increase in body mass and a 37% increase in the length of their lumbar spines. The lumbar vertebrae were the only skeletal structures that exhibited this puberty-like growth. After colony separation, body mass and lumbar vertebrae growth rates peaked and remained elevated for several weeks before returning to control levels--suggestive of a puberty-like 'growth spurt'. Although previous studies have characterized pregnancy-induced lumbar spine elongation in female mole-rats, we demonstrate a significant change in the body morphology of female mole-rats after removal from reproductive suppression but before the first pregnancy.