Abstract:
Naked mole-rats occur in large colonies where usually a single queen monopolizes reproduction.
Queen succession occurs from within usually as a result of aggressive encounters with subordinate
females that queue for reproductive succession following colony instability, which inevitably
results in death of either the queen or the challenging conspecific. We monitored a queen
succession following the death of the breeding male in a colony of the naked mole-rat,
Heterocephalus glaber, prior to, during as well as after replacement of the original breeding
female. The response of the pituitary luteotrophs was investigated in the non-reproductive
females during this period of instability by the administration of endogenous gonadotrophin
releasing hormone (GnRH) and evaluating the subsequent luteinising hormone (LH) response
in the blood. Larger and older non-breeding females engaged in aggressive encounters that
culminated in death. The new breeding successor which arose from within the colony was
a large female who continued to procreate. The six non-breeding females that were killed
during reproductive takeover were larger and older females which exhibited elevated basal
circulating LH concentrations as well as increased pituitary sensitivity as measured by the
amount of releasable LH to an exogenous GnRH challenge. By contrast, non-breeding females
that survived the succession were smaller and younger animals with reduced basal and GnRH
challenged LH concentrations. Likewise, five non-breeding males which were heavier and older
than those non-breeding males which survived were killed. These animals did not, however,
show elevated basal or exogenous GnRH challenged LH concentrations when compared to the
surviving males. The non-breeding animals of both sexes which survived the reproductive
takeover event represented individuals which posed a minimal threat to the new successor and
hence promoted the continuation of the marked reproductive skew that is prevalent in this
highly inbred colonial subterranean hystricomorph.
