title: Detection of hydrodynamic stimuli by the postcranial body of Florida manatees (Trichechus manatus latirostris).
abstract: Manatees live in shallow, frequently turbid waters. The sensory means by which they navigate in these conditions are unknown. Poor visual acuity, lack of echolocation, and modest chemosensation suggest that other modalities play an important role. Rich innervation of sensory hairs that cover the entire body and enlarged somatosensory areas of the brain suggest that tactile senses are good candidates. Previous tests of detection of underwater vibratory stimuli indicated that they use passive movement of the hairs to detect particle displacements in the vicinity of a micron or less for frequencies from 10 to 150 Hz. In the current study, hydrodynamic stimuli were created by a sinusoidally oscillating sphere that generated a dipole field at frequencies from 5 to 150 Hz. Go/no-go tests of manatee postcranial mechanoreception of hydrodynamic stimuli indicated excellent sensitivity but about an order of magnitude less than the facial region. When the vibrissae were trimmed, detection thresholds were elevated, suggesting that the vibrissae were an important means by which detection occurred. Manatees were also highly accurate in two-choice directional discrimination: greater than 90% correct at all frequencies tested. We hypothesize that manatees utilize vibrissae as a three-dimensional array to detect and localize low-frequency hydrodynamic stimuli.
authors.affiliation: Science and Conservation, Pittsburgh Zoo & PPG Aquarium, 1 Wild Place, Pittsburgh, PA, 15206, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Gaspard
authors.affiliation: Division of Social Sciences, New College of Florida, 5800 Bay Shore Rd., Sarasota, FL, 34243, USA. bauer@ncf.edu.|Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, FL, 34236, USA. bauer@ncf.edu.
authors.forename: Gordon B
authors.identifier: http://orcid.org/0000-0002-7833-1489
authors.initials: GB
authors.lastname: Bauer
authors.affiliation: Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, FL, 34236, USA.|Loggerhead Instruments, 6576 Palmer Park Circle, Sarasota, FL, 34238, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Mann
authors.affiliation: Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, FL, 34236, USA.
authors.forename: Katharine
authors.initials: K
authors.lastname: Boerner
authors.affiliation: Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, FL, 34236, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Denum
authors.affiliation: Division of Social Sciences, New College of Florida, 5800 Bay Shore Rd., Sarasota, FL, 34243, USA.
authors.forename: Candice
authors.initials: C
authors.lastname: Frances
authors.affiliation: Department of Physiological Sciences, Aquatic Animal Health Program, University of Florida, College of Veterinary Medicine, Gainesville, FL, 32610, USA.
authors.forename: Roger L
authors.initials: RL
authors.lastname: Reep
mesh_terms: D000818:Animals; D005431:Florida; D057446:Hydrodynamics; D008297:Male; D014110:Touch / Q000502:physiology*; D020457:Trichechus manatus / Q000502:physiology*; D014732:Vibration; D014738:Vibrissae / Q000502:physiology*
keywords: Hydrodynamic; Manatee; Sirenian; Tactile; Vibrissae