Penile spines affect copulatory behaviour in a primate ( Callithrix jacchus)

Androgen-dependent, keratinized “spines” occur on the glans penis in many rodents, primates and other mammals. Since penile spines overlie dermal tactile receptors, they may play a role in copulatory behaviour. An experiment was conducted to test this hypothesis. Sixteen sexually experienced adult male marmosets were paired with ovariectomized females before, and after, removal of penile spines (using thioglycollate cream applied to the glans under anaesthesia) or a sham operation. Spine removal resulted in an increased duration of preintromission pelvic thrusting (mean±s.e.m. from 6.87±1.09 to 14.94±3.32 s, p=0.05) and of intromitted thrusting (from 1.73±0.11 to 2.0±0.11 s, p