Evidence that primer pheromones do not cause social suppression of reproduction in male and female naked mole-rats (Heterocephalus glaber)

in Reproduction

The role of chemical cues in mediating the reproductive suppression of nonbreeding males and females in colonies of naked mole-rats (Heterocephalus glaber) was examined by comparing reproductive activation in isolated nonbreeders with that of isolated nonbreeders maintained in olfactory and gustatory contact with their parent colony. Animals were either removed from their colony and paired directly with a member of the opposite sex from the same colony, or were removed, housed singly for 40 days, and then paired with a member of the opposite sex from the same parent colony that had also been housed singly for 40 days. Approximately half of these separated animals received a daily transfer of soiled bedding and litter from their parent colony. In females, there was no significant difference between the control and bedding transfer group, in the time taken from separation to the first sustained increase of urinary progesterone above 2 ng mg−1 Cr indicative of the luteal phase of an ovarian cycle (7.8 ± 2.6 versus 9.4 ± 2.0 days, respectively). In both control and bedding transfer groups, singly-housed females commenced ovarian cyclicity, revealing that the presence of a male was not required for reproductive activation and ovulation. In males, concentrations of both urinary testosterone and plasma LH increased after separation from their parent colonies in both control and bedding transfer groups, to reach values equivalent to those of breeding males. The mean time between separation and a rise in urinary testosterone to amounts observed in breeding males (24 ng mg−1 Cr) was not significantly different between control and bedding transfer groups (5.0 ± 1.4 versus 4.4 ± 1.7 days, respectively). There was no significant difference in either plasma LH or urinary testosterone concentrations between the control and bedding transfer groups before or after separation from their parent colonies. These results suggest that primer pheromones from urine, or other secretions contained in soiled bedding and litter, do not play a major role in the suppression of reproduction in nonbreeding male or female naked mole-rats.

 

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