title: The sea lamprey has a primordial accessory olfactory system.
abstract: BACKGROUND
  A dual olfactory system, represented by two anatomically distinct but spatially proximate chemosensory epithelia that project to separate areas of the forebrain, is known in several classes of tetrapods. Lungfish are the earliest evolving vertebrates known to have this dual system, comprising a main olfactory and a vomeronasal system (VNO). Lampreys, a group of jawless vertebrates, have a single nasal capsule containing two anatomically distinct epithelia, the main (MOE) and the accessory olfactory epithelia (AOE). We speculated that lamprey AOE projects to specific telencephalic regions as a precursor to the tetrapod vomeronasal system.
  
  
  RESULTS
  To test this hypothesis, we characterized the neural circuits and molecular profiles of the accessory olfactory epithelium in the sea lamprey (Petromyzon marinus). Neural tract-tracing revealed direct and reciprocal connections with the dorsomedial telencephalic neuropil (DTN) which in turn projects directly to the dorsal pallium and the rostral hypothalamus. High-throughput sequencing demonstrated that the main and the accessory olfactory epithelia have virtually identical profiles of expressed genes. Real time quantitative PCR confirmed expression of representatives of all 3 chemoreceptor gene families identified in the sea lamprey genome.
  
  
  CONCLUSIONS
  Anatomical and molecular evidence shows that the sea lamprey has a primordial accessory olfactory system that may serve a chemosensory function.
authors: Department of Fisheries and Wildlife, Michigan State University, 480 Wilson Road, East Lansing, MI 48824, USA. liweim@msu.edu.
authors: Steven
authors: S
authors: Chang
authors: Yu-Wen
authors: YW
authors: Chung-Davidson
authors: Scot V
authors: SV
authors: Libants
authors: Kaben G
authors: KG
authors: Nanlohy
authors: Matti
authors: M
authors: Kiupel
authors: C Titus
authors: CT
authors: Brown
authors: Weiming
authors: W
authors: Li
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology; D007031:Hypothalamus / Q000502:physiology; D007798:Lampreys / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D009833:Olfactory Pathways; D059467:Transcriptome; D019147:Vomeronasal Organ / Q000378:metabolism
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