Fukomys anselli, also known as Ansell's mole rat, is a subterranean, highly social (so-called eusocial) rodent that lives in Africa. These mole rats typically form multigenerational families consisting of a single monogamous breeding pair and their nonreproductive offspring. Research on other mammals suggests that oxytocin (OT) and vasopressin (VP) as well as the distribution of OT- and VP-receptors may influence social behavior and pair bonding. Recent studies on eusocial naked mole rats have shown a possible relation between sociality and OT-immunoreactive (OT-ir) processes. In this study, we examined expression patterns of OT and VP in the brains of F. anselli and the common Sprague-Dawley (SD) laboratory rat. As in other species, the majority of OT-ir and VP-ir neurons was found in the paraventricular (Pa) and supraoptic (SO) nuclei, and scattered labeling throughout the preoptic and anterior hypothalamic areas. We found no difference in either quality or quantity of OT- and VP-ir neurons between individuals of different social and reproductive ranks. Equally unexpected was the finding of specific OT-immunoreactivity in neurons of the mammillary complex of F. anselli that was not found in SD rats. Further studies are needed to determine whether these mammillary OT-ir neurons are causally related to monogamy in F. anselli and whether these correlates of monogamy are found in other species.
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