Teasing apart socially‐induced infertility in non‐reproductive female Damaraland mole‐rats, Fukomys damarensis (Rodentia: Bathyergidae)

Abstract

The Damaraland mole-rat is a subterranean mammal exhibiting extreme reproductive skew with a single reproductive female in each colony responsible for procreation. Non-reproductive female colony members are physiologically suppressed while in the colony exhibiting reduced concentrations of plasma luteinizing hormone (LH) and a decreased response of the pituitary, as measured by the release of bioactive LH, to an exogenous dose of gonadotrophin releasing hormone (GnRH). Removal of the reproductive female from the colony results in an elevation of LH and an enhanced response of the pituitary to a GnRH challenge in non-reproductive females comparable to reproductive females, implying control of reproduction in these individuals by the reproductive female. The Damaraland mole-rat is an ideal model for investigating the physiological and behavioural mechanisms that regulate the hypothalamopituitary-gonadal axis. In contrast, we know less about the control of reproduction at the level of the hypothalamus. The immunohistochemistry of the GnRH system of both reproductive and non-reproductive female Damaraland mole-rats has revealed no significant differences with respect to morphology, distribution or numbers of immunoreactive GnRH perikarya. We

The challenge hypothesis across taxa: social modulation of hormone titres in vertebrates and insects

“…Many studies have found that subordinate status per se, rather than correlates of subordinate status such as age or condition, is responsible for the reduced hormone titres in subordinates (birds: Brouwer et al, 2009;Peters, Astheimer, & Cockburn, 2001;Reyer, Dittami, & Hall, 1986;fish: Kustan, Maruska, & Fernald, 2012;mammals: Bennett, 2011;Young, Oosthuizen, Lutermann, & Bennett, 2010). Furthermore, subordinates will often rapidly upregulate hormone titres when the dominant is removed (Bennett, 2011;Brouwer et al, 2009;Kustan et al, 2012), suggesting that the presence of the dominant causes the prolonged reduction in subordinate hormone titres.…”

The long-lived queen: reproduction and longevity in female eusocial Damaraland mole-rats (Fukomys damarensis)

“…Reproductive suppression in Damaraland mole-rats is due to two factors: incest avoidance and social environment (Cooney & Bennett 2000;Bennett 2011), and subordinate females possess functionally developed ovaries, but do not ovulate (Bennett 1994;Bennett et al 1994;Molteno & Bennett 2000). Although some individuals disperse and found new colonies, most non-reproductive members stay in their natal colony ; it is estimated that 90% of the population never breed (Faulkes & Bennett 2001).…”

The Long-Lived Queen: Reproduction and Longevity in Female Eusocial Damaraland Mole-Rats (Fukomys damarensis)

“…The social structure of naked mole-rats is analogous to eusocial ant, termite and some bee species (Jarvis 1981), and it has been argued that the only other mammal that exhibits this extreme type of sociality is another bathyergid species, the Damaraland mole-rat (Fukomys damarensis; . Reproductive suppression in Damaraland mole-rats is due to two factors: incest avoidance and social environment (Cooney & Bennett 2000;Bennett 2011), and subordinate females possess functionally developed ovaries, but do not ovulate (Bennett 1994;Bennett et al 1994;Molteno & Bennett 2000). Although some individuals disperse and found new colonies, most non-reproductive members stay in their natal colony ; it is estimated that 90% of the population never breed (Faulkes & Bennett 2001).…”