The influence of status and the social environment on energy stores in a social fish.

This study explores how muscle and liver energy stores are linked with social status and the social environment in Neolamprologus pulcher, a cooperatively breeding fish that lives in colonies comprised of up to 200 distinct social groups. Subordinate muscle energy stores were positively correlated with the number of neighbouring social groups in the colony, but this pattern was not observed in dominant fish. Further, liver energy stores were smaller in dominants living at the edge of the colony compared to those living in the colony centre, with no differences among subordinates in liver energy stores. Subordinate fish may build up the large energy stores in the muscles to fuel rapid growth after dispersal, which could occur more frequently in high-density environments. Dominant fish may use the more easily mobilized energy stores in the liver to fuel daily activities, which could be more energetically demanding on the edge of the colony as a result of the increased predation defence needed on the edge. Overall, this study demonstrates that both subordinate and dominant physiology in N. pulcher varies with characteristics of the social environment. Further, dominant and subordinate energy storage strategies appear to differ due to status-dependent variation in daily activities and variation in the need to prepare for future reproductive or dispersal opportunities.