The research described here characterizes a unique neuromuscular system involved in reproductive behavior – the foam production system of the male Japanese quail (Coturnix japonica). Male quail produce a large amount of foam that is transferred to the female during copulation, enhancing male fertilization success. The source is the foam gland complex, a large sexually dimorphic, androgen sensitive, external protuberance of the dorsal cloaca, consisting of glandular units interdigitated with striated muscle fibers of the sphincter cloacae muscle (mSC). Electromyographic (EMG) analysis of mSC activity in freely moving males interacting with females revealed different characteristics of the EMG signal during copulation, voiding of excreta, and other mSC movement. The amount of mSC activity and also the amount of foam produced were greatly increased by the presence of a female behind a screen. Denervation of mSC eliminated normal mSC movement and also abolished foam production, confirming that mSC activity is the mechanism for foam production. The spinal cord locations of the motoneurons innervating the major cloacal muscles, including mSC, were determined by injecting cholera-toxin conjugated horseradish peroxidase into each muscle. Labelled somata with multiple primary dendrites were located in Area IX of the lateral motor column of synsacral segments 7, 8, or 9 or 8, 9, and 10. The motoneurons serving mSC were intermingled with those projecting to the other cloacal muscles, but there were differences in the rostral-caudal placement of these neural populations. Thus mSC activity is an integral part of the male’s reproductive behavior, mSC activity can be socially stimulated, and mSC activity occurring in anticipation of copulation is likely to be functionally significant. Continued investigation of this highly accessible system has the potential to shed light on the mechanisms by which complex motor acts are produced and hormonally regulated.

In order to determine the critical period(s) during which estrogen alters sexually dimorphic behavior and neuroanatomy in zebra finches (Poephila guttata), nestlings were injected daily with 20 micrograms estradiol benzoate (EB) during posthatching week 1, week 2, week 3, or weeks 1, 2, and 3. At 7 months of age, birds were implanted with testosterone propionate and tested with female partners for singing, dancing, and copulatory mounting. Brains were subsequently processed for morphometry, and the volumes of the song system nuclei HVC, area X, and RA and the soma sizes and densities of neurons in RA were determined. Males given EB during week 1 failed to mount. Females given EB during week 1 were fully masculinized with respect to dancing and RA neuron soma size and density, and were partially masculinized with respect to song nuclei volumes and singing. Treatment beginning after week 1 was ineffective or less effective for all measures. Only for RA neuron measures was treatment for all three weeks more effective than week 1 treatment. Thus the first post-hatching week is the most influential period of those tested for effects of exogenous estrogen on sexual differentiation in this species, and is a period during which both masculinization of females and demasculinization of males is possible.