Lesions of gonadotropin-releasing hormone-immunoreactive terminal nerve cells: effects on the reproductive behavior of male dwarf gouramis.

Functions of the terminal nerve (TN) are largely unknown. To examine whether gonadotropin-releasing hormone (GnRH)-immunoreactive TN cells (TN-GnRH cells) are involved in the control of reproductive behavior, effects of lesions of TN-GnRH cells were studied in male dwarf gouramis, Colisa lalia. After bilateral electrolytic lesion, a characteristic impairment was observed in one of the repertoires of male reproductive behavior, nest-building. The occurrence of mating trials in which males showed no nest-building was increased. However, the incidence of nest-building behavior during postoperative trials was not affected by the lesion. No impairment was observed in other reproductive repertoires. These results suggest that (1) TN-GnRH cells are involved in the control of the threshold for nest-building behavior initiation and (2) TN-GnRH cells are not a prerequisite for other aspects of reproductive behavior in the male gouramis.