EXPRESSION OF FOS-LIKE IMMUNOREACTIVITY IN THE HYPOTHALAMUS OF THE RING DOVE (STREPTOPELIA-RISORIA) AT THE ONSET OF INCUBATION

Fos immunocytochemistry was used in the ring dove (Streptopelia risoni a) to identify areas in the forebrain and hypothalamus which might be involved in the expression of incubation behaviour and the associated changes in neuroendocrine function. In this species, both sexes partic ipate in incubation which becomes fully established after laying the s econd egg in the two egg clutch. The eggs hatch after 14-15 days incub ation. Observations were made in both sexes 16-18 h after laying the f irst egg, 3-5 h after laying the second egg, and after 12-14 days of i ncubation. Non-breeding birds were used as controls. Fos-labelled cell s were observed in several forebrain areas in both sexes irrespective of reproductive status but their numbers did not change during incubat ion. In the hypothalamus, very few fos-labelled cells were seen in non -breeding birds but appeared in both sexes in the nucleus preopticus m edialis after egg laying and after 12-14 days of incubation. Fos-label led cells also appeared in the nucleus tuberis (=arcuate nucleus) in b oth sexes after laying the first or second egg and less abundantly, af ter 12-14 days incubation. Additionally, in males only, fos-labelled c ells were seen after the laying of the first and second eggs in the ro stral area of the nucleus tuberis close to the walls of the third vent ricle. These observations suggest that the fos-labelled cells in the n ucleus preopticus medialis may be involved in the expression of incuba tion behaviour while those in the nucleus tuberis may be involved in t he regulation of gonadotrophin or prolactin secretion.