A Sex Pheromone System in Goldfish: Is the Nervus Terminalis Involved?" J. G. DULKA, N. E. STACEY, P. W. SORENSEN, G. J. VAN DER KRAAK, AND T. A. MARCHANT zy Department of Zoology University of Alberta Edmonton, Alberta T6G 2E9. Canada INTRODUCTION zyxw Recently the nervus terminalis (NT) has attracted considerable attention as a putative chemosensory system which may mediate responses to sex pheromones in vertebrates.' This proposed function of the NT is based on correlations between anatomical and neurobehavioral studies conducted primarily on goldfish and other teleost fish. Anatomic findings suggest that the NT serves a function distinct from that of the classical olfactory system. In goldfish, NT ganglion cells in the olfactory nerve and bulb send peripheral processes to the olfactory epithelium.'.' and central processes, via the medial olfactory tracts (MOT), to telencephalic and preoptic nuclei'.'" that control a variety of reproductive functions."" In addition, some NT cells project to the retina and are immunoreactive for gonadotropin-releasing hormone (GnRH)?"-'' A number of neurobehavioral studies provide indirect evidence that the NT could be involved with pheromone reception in goldfish. However, the function of the NT has been proposed on the basis of its anatomic association with the MOT, which contain both secondary olfactory fibers and projections of the NT. Selective stimulation of the MOT evokes sperm release in goldfish, possibly through activation of the NT.'.14 Brain lesions that destroy the MOT and NT terminal fields in the ventral telencephalon and preoptic area (POA) reduce male spawning behavior in g~ldfish?~.'~.'~ Because male sexual behavior is triggered by the release of a female sex pheromone," the lesions may reduce behavior by disrupting the pheromone input. However, it has not been determined whether the behavioral deficits resulting from lesions of the MOT or specific brain sites are due to destruction of the terminalis system or of secondary olfactory fibers in the MOT.'* One major impediment in identifying NT functions has been an inadequate un- derstanding of fish pheromone systems. In most cases in which pheromones are suggested to operate, neither the chemical identity of the putative pheromone nor the 'This research was supported by the Alberta Heritage Foundation for Medical Research and the Natural Sciences and Engineering Research Council of Canada. zyxw 411