Sexual inhibition in a prosimian primate: a pheromone-like effect

Area of Science:

• Primate reproductive endocrinology
• Olfactory communication in mammals
• Social behavior and physiology

Background:

• Microcebus murinus exhibits photoperiod-dependent sexual cycles with significant testosterone level variations.
• Captive grouping of this species leads to social hierarchies and reproductive dysfunction in non-dominant males.
• Olfactory cues are crucial for social structure in this primate species.

Purpose of the Study:

• To investigate the impact of dominant urine odor on plasma testosterone and cortisol levels in male Microcebus murinus.
• To determine if dominant urine odor alone can induce sexual inhibition in conspecific males.
• To assess the reversibility of these endocrine changes upon removal of the dominant odorant signal.

Main Methods:

• Measuring plasma testosterone and cortisol levels in male Microcebus murinus under different olfactory conditions.
• Exposing non-dominant males to dominant urine odor and observing subsequent hormonal changes.
• Isolating males from dominant urine odor to assess the recovery of hormone concentrations.

Main Results:

• Exposure to dominant urine odor significantly decreased plasma testosterone and increased plasma cortisol levels.
• Dominant urine odor alone was sufficient to induce these endocrine modifications.
• Removal of dominant urine odor led to the normalization of testosterone and cortisol levels, even in naive individuals.

Conclusions:

• A pheromone-like mechanism likely mediates sexual inhibition in male Microcebus murinus exposed to dominant urinary signals.
• The endocrine response to social olfactory cues is modulated by seasonal reproductive cycles and other factors.
• Olfactory signals play a critical role in regulating reproductive physiology and social dynamics in this primate species.