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Development of the Olfactory and Terminalis Systems in Whales and Dolphins

  • Helmut A. Oelschläger

Abstract

In the early ontogenesis of mammals, the chemoreceptor systems of the nose (olfactory and accessory olfactory complex) originate from the olfactory placode together with the terminalis system (Oelschläger and Buhl, 1985a, b; Buhl and Oelschläger, 1986; Oelschläger, 1988, 1989). The embryonal chemoreceptor epithelia send axons and possibly Schwann cells to the rostrobasal part of the telencephalon. Here they induce the formation of an olfactory bulb, which is apparent in an evagination of the telencephalic wall, and of an accessory olfactory bulb, which may be reduced later together with the vomeronasal nerve and Jacobson’s organ. The terminalis system, however, the functional implications of which are only imperfectly known, is represented by neuroblasts which migrate from the olfactory placode to the rostromedial extremity of the basal telencephalic hemisphere, adjacent to the olfactory bulb. While the terminalis neuroblasts send out central processes to the brain wall, they obviously retain connections with the dorsomedial part of the olfactory placode. In the adult stage of mammals the terminalis system, which consists of a ganglionated fiber plexus, connects the olfactory and respiratory mucosa of the nasal septum with rostral and basal parts of the prosencephalon. The neurons belong to at least two subpopulations of cells which differ in the size of their perikarya and nuclei. Whether these two types of neurons are identical with cell populations characterized with histochemical and immunocytochemical methods (Bojsen-Møller, 1975; Wirsig and Leonard, 1986; Silverman and Krey, 1978; Oelschläger and Burda, this volume; Oelschläger and Northcutt, 1991, submitted), however, is not clear. Taken as a whole, the terminalis system may innervate arteries of the basal forebrain and of glands and blood vessels in the mucous membrane lining the septal wall of the nasal cavity (Johnston, 1914; Larsell, 1918, 1950). A fraction of mostly bipolar termina-lis neurons immunoreactive for luteinizing hormone-releasing hormone (LHRH) obviously are involved in the establishment and maturation of the brainpituitary-gonadal circuit (Jennes and Stumpf, 1980; Schwanzel-Fukuda et al., 1981, 1985; Oelschläger and Northcutt, 1991, submitted). In the ontogenesis of rats, LHRH immunoreactivity first appears in peripheral (nasal) and central (meningeal) ganglion cells of the nervus terminalis (Jennes and Stumpf, 1980; Schwanzel-Fukuda and Silverman, 1980; Schwanzel-Fukuda et al., 1985, 1988; Jennes, 1989). Correspondingly, after the establishment of the hypothalamohypophyseal-gonadal axis in rat and mouse, the number of LHRH neurons seems to decrease from late fetal stages onward (Schwanzel-Fukuda et al., 1987; Schwanzel-Fukuda and Pfaff, 1989).

Keywords

Olfactory Bulb Cribriform Plate Harbor Porpoise Baleen Whale Accessory Olfactory Bulb 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Buhl, E.H., and Oelschläger, H.A., 1986, Ontogenetic development of the nervus terminalis in toothed whales. Evidence for its non-olfactory nature, Anat.Embryol. 173: 285–294.PubMedCrossRefGoogle Scholar
  2. Demski, L.S., Ridgway, S.H., and Schwanzel-Fukuda, M., 1990, The terminal nerve of dolphins: Gross structure, histology and luteinizing hormone–releasing hormone immunocytochemistry, Brain Behay.Evol. 36: 249–261.CrossRefGoogle Scholar
  3. Heyning, J.E., and Mead, J.G., 1990, Evolution of the nasal anatomy of cetaceans, in: “Sensory Abilities of Cetaceans”, J. Thomas and R. Kastelein, eds. (NATO ASI Series A, Vol. 196 ) Plenum Press, New York, pp. 67–79.Google Scholar
  4. Oelschläger, H.A., 1988, Persistence of the nervus terminalis in adult bats: A morphological and phylogenetical approach, Brain Behay.Evol. 32: 330339.Google Scholar
  5. Oelschläger, H.A., 1989, Early development of the olfactory and terminalis systems in baleen whales, Brain Behay.Evol. 34: 171–183.CrossRefGoogle Scholar
  6. Oelschläger, H.A., 1990, Evolutionary morphology and acoustics in the dolphin skull, in: “Sensory Abilities of Cetaceans, J.Thomas and R.Kastelein, eds. (NATO ASI Series A, Vol. 196 ) Plenum Press, New York, pp. 137–162.Google Scholar
  7. Oelschläger, H.A., and Buhl, E.H., 1985b, Development and rudimentation of the peripheral olfactory system in the harbor porpoise Phocoena phocoena (Mammalia: Cetacea), J.Morphol. 184: 351–360.CrossRefGoogle Scholar
  8. Oelschläger, H.A., and Burda, H. (this volume), LHRH-immunocytochemistry in the nervus terminalis of mammals.Google Scholar
  9. Oelschläger, H.A., und Northcutt, R.G., 1991, Luteinisierendes Hormon–Releasing Hormon (LHRH) in Nervus terminalis und Vorderhirn der Fledermaus Eptesicus fuscus. Eine immuncytochemische Untersuchung. Verh.Anat.Ges. 84 (Anat.Anz.Suppl. 168): 499–500.Google Scholar
  10. Oelschläger, H.A., and Northcutt, R.G., 1991, Immunocytochemical localization of luteinizing hormone-releasing hormone (LHRH) in the nervus terminalis and brain of the big brown bat, Eptesicus fuscus (Journal of Comparative Neurology, in press).Google Scholar
  11. Oelschläger, H.A., Buhl, E.H., and Dann, J.F., 1987, Development of the nervus terminalis in mammals including toothed whales and humans, in: “The Terminal Nerve (Nervus Terminalis). Structure, Function and Evolution”, L.S. Demski and M. Schwanzel-Fukuda, eds., Ann.NY Acad.Sci. 519: 447–464.Google Scholar
  12. Ridgway, S.H., Demski, L.S., Bullock, T.H., and Schwanzel-Fukuda, M., 1987, The terminal nerve in odontocete cetaceans, in: “The Terminal Nerve (Nervus Terminalis). Structure, Function and Evolution”, L.S. Demski and M. Schwanzel-Fukuda, eds., Ann.NY Acad.Sci. 519: 201–212.Google Scholar
  13. Sinclair, J.G., 1951, The terminal olfactory complex in the porpoise. Tex. J.Sci. 3: 251.Google Scholar
  14. Sinclair, J.G., 1966, The olfactory complex of dolphin embryos, Tex.Rep.Biol. Med. 24: 426–431.PubMedGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1992

Authors and Affiliations

  • Helmut A. Oelschläger
    • 1
  1. 1.Dept.of AnatomyJ.W.Goethe-UniversityFrankfurt am Main 70Germany

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