title: Mucus trail tracking in a predatory snail: olfactory processing retooled to serve a novel sensory modality.
abstract: BACKGROUND
  The rosy wolfsnail (Euglandina rosea), a predatory land snail, finds prey snails and potential mates by following their mucus trails. Euglandina have evolved unique, mobile lip extensions that detect mucus and aid in following trails. Currently, little is known of the neural substrates of the trail-following behavior.
  
  
  METHODS
  To investigate the neural correlates of trail following we used tract-tracing experiments in which nerves were backfilled with either nickel-lysine or Lucifer yellow, extracellular recording of spiking neurons in snail procerebra using a multielectrode array, and behavioral assays of trail following and movement toward the source of a conditioned odor.
  
  
  RESULTS
  The tract-tracing experiments demonstrate that in Euglandina, the nerves carrying mucus signals innervate the same region of the central ganglia as the olfactory nerves, while the electrophysiology studies show that mucus stimulation of the sensory epithelium on the lip extensions alters the frequency and pattern of neural activity in the procerebrum in a manner similar to odor stimulation of the olfactory epithelium on the optic tentacles of another land snail species, Cantareus aspersa (previously known as Helix aspersa). While Euglandina learn to follow trails of novel chemicals that they contact with their lip extensions in one to three trials, these snails proved remarkably resistant to associative learning in the olfactory modality. Even after seven to nine pairings of odorant molecules with food, they showed no orientation toward the conditioned odor. This is in marked contrast to Cantareus snails, which reliably oriented toward conditioned odors after two to three trials.
  
  
  CONCLUSIONS
  The apparent inability of Euglandina to learn to associate food with odors and use odor cues to drive behavior suggests that the capability for sophisticated neural processing of nonvolatile mucus cues detected by the lip extensions has evolved at the expense of processing of odorant molecules detected by the olfactory system.
authors.affiliation: Department of Biology, Delaware State University 1200 North Dupont Highway, Dover, Delaware, 19901.
authors.forename: Kinjal
authors.initials: K
authors.lastname: Patel
authors.affiliation: Department of Biology, Delaware State University 1200 North Dupont Highway, Dover, Delaware, 19901.
authors.forename: Nagma
authors.initials: N
authors.lastname: Shaheen
authors.affiliation: Department of Physical Therapy and Rehabilitation Service, University of Kansas Medical Center Kansas City, Kansas, 66160.
authors.forename: Jessica
authors.initials: J
authors.lastname: Witherspoon
authors.affiliation: Department of Biology, Delaware State University 1200 North Dupont Highway, Dover, Delaware, 19901.
authors.forename: Natallia
authors.initials: N
authors.lastname: Robinson
authors.affiliation: Department of Biology, Delaware State University 1200 North Dupont Highway, Dover, Delaware, 19901.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Harrington
mesh_terms: D000818:Animals; D001245:Association Learning / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D055724:Electrophysiological Phenomena; D017952:Ganglia, Invertebrate / Q000502:physiology*; D006372:Helix, Snails / Q000502:physiology; D008124:Locomotion / Q000502:physiology; D009093:Mucus; D009831:Olfactory Mucosa / Q000502:physiology*; D055696:Olfactory Perception / Q000502:physiology*; D012908:Snails / Q000502:physiology*
keywords: Euglandina; invertebrate model; multielectrode array; olfaction; sensory learning; trail following