|
|
Reep, Roger Lyons; Gaspard, Joseph C., III; Sarko, Diana K.; Rice, Frank L.; Mann, David A.; Bauer, Gordon B.
(detail)
|
| |
|
2011 |
Manatee vibrissae: evidence for a "lateral line" function.
Annals of the New York Academy of Sciences DOI: 10.1111/j.1749-6632.2011.05992.x. Apr. 2011.
–Aquatic mammals use vibrissae to detect hydrodynamic stimuli over a range from 5 to 150 Hz, similar to the range detected by lateral line systems in fishes and amphibians. Manatees possess ?5,300 vibrissae distributed over the body, innervated by ?209,000 axons. This extensive innervation devoted to vibrissae follicles is reflected in enlarged, elaborate somatosensory regions of the gracile, cuneate, and Bischoff's brain-stem nuclei, ventrobasal thalamus, and presumptive somatosensory cortex. Our preliminary psychophysical testing indicates that in Florida and Antillean manatees the Weber fraction for detection thresholds for grating textures ranges from 0.025 to 0.14. At the lower end of this range, sensitivity is comparable to human index finger thresholds. For hydrodynamic stimuli of 5–150 Hz, detection threshold levels for manatees using facial or postfacial vibrissae were substantially lower than those reported for harbor seals and similar to reports of sensitivity for the lateral line systems of some fish. Our findings suggest that the facial and postfacial vibrissae are used to detect hydrodynamic stimuli, whereas only the facial vibrissae are used for direct contact investigation.
|
|
|
Bauer, Gordon B.; Gaspard, Joseph C., III; Colbert, Debborah E.; Leach , Jennifer B.; Stamper , Sarah A.; Mann, David; Reep, Roger Lyons
(detail)
|
| |
|
2012 |
Tactile discrimination of textures by Florida manatees (Trichechus manatus latirostris).
Mar. Mamm. Sci. 28(4): E456-E471. 4 figs. DOI: 10.1111/j.1748-7692.2012.00565.x Oct. 2012 (first published online June 13, 2012).
–ABSTRACT: Two male Florida manatees (Trichechus manatus latirostris) demonstrated sensitive tactile discrimination in a two-alternative forced choice task, using a modified staircase method. Stimuli were acrylic plates with vertical gratings of ridges and grooves. The standard stimulus, present on every trial, had 2 mm gratings and the comparison stimuli had wider gratings. The blindfolded subjects were trained to demonstrate discrimination by pressing the target with wider gratings. Discrimination thresholds (75% correct) for the subjects were 2.05 mm and 2.15 mm, corresponding to Weber fractions of 0.025 and 0.075, respectively. These results indicate thresholds on similar stimuli comparable to humans (index finger tasks) and better than harbor seals, Phoca vitulina, and the closely related Antillean manatee, Trichechus manatus manatus. Memory for the tactile task was quite stable for both subjects, over 2 yr in the case of one of the subjects. Video analysis of responses indicated that bristle-like hairs, perioral bristles, and skin on the oral disk were involved in the discrimination response.
|
|
|
Gaspard, Joseph C., III; Bauer, Gordon B.; Reep, Roger L.; Dziuk, Kimberly; Read, LaToshia; Mann, David A.
(detail)
|
| |
|
2013 |
Detection of hydrodynamic stimuli by the Florida manatee (Trichechus manatus latirostris).
Jour. Comp. Physiol. A - Neuroethology Sensory Neural & Behav. Physiol. 199(6): 441-450. 4 tabs. 5 figs. DOI: 10.1007/s00359-013-0822-x. May 10, 2013.
–ABSTRACT: Florida manatees inhabit the coastal and inland waters of the peninsular state. They have little difficulty navigating the turbid waterways, which often contain obstacles that they must circumnavigate. Anatomical and behavioral research suggests that the vibrissae and associated follicle–sinus complexes that manatees possess over their entire body form a sensory array system for detecting hydrodynamic stimuli analogous to the lateral line system of fish. This is consistent with data highlighting that manatees are tactile specialists, evidenced by their specialized facial morphology and use of their vibrissae during feeding and active investigation/manipulation of objects. Two Florida manatees were tested in a go/no-go procedure using a staircase method to assess their ability to detect low-frequency water movement. Hydrodynamic vibrations were created by a sinusoidally oscillating sphere that generated a dipole field at frequencies from 5 to 150 Hz, which are below the apparent functional hearing limit of the manatee. The manatees detected particle displacement of less than 1??m for frequencies of 15–150 Hz and of less than a nanometer at 150 Hz. Restricting the facial vibrissae with various size mesh openings indicated that the specialized sensory hairs played an important role in the manatee's exquisite tactile sensitivity.
|
|
|
Colbert-Luke, Debborah E.; Gaspard, Joseph C., III; Reep, Roger Lyons; Bauer, Gordon B.; Dziuk, Kimberly; Cardwell, Adrienne; Mann, David A.
(detail)
|
| |
|
2015 |
Eight-choice sound localization by manatees: performance abilities and head related transfer functions.
Jour. Compar. Physiol. A 201(2): 249-259. Feb. 2015.
–ABSTRACT: Two experiments investigated the ability and means by which two male Florida manatees (Trichechus manatus latirostris) may determine the direction of a sound source. An eight-choice discrimination paradigm was used to determine the subjects' sound localization abilities of five signal conditions covering a range of frequencies, durations, and levels. Subjects performed above the 12.5 % chance level for all broadband frequencies and were able to localize sounds over a large level range. Errors were typically located to either side of the signal source location when presented in the front 180° but were more dispersed when presented from locations behind the subject. Front-to-back confusions were few and accuracy was greater when signals originated from the front 180°. Head-related transfer functions were measured to determine if frequencies were filtered by the manatee body to create frequency-specific interaural level differences (ILDs). ILDs were found for all frequencies as a function of source location, although they were largest with frequencies above 18 kHz and when signals originated to either side of the subjects. Larger ILDs were found when the signals originated behind the subjects. A shadowing-effect produced by the body may explain the relatively low occurrence of front-back confusions in the localization study.
|
|
|
Gaspard, Joseph C., III; Bauer, Gordon B.; Mann, David A.; Boerner, Katharine; Denum, Laura; Frances, Candice; Reep, Roger Lyons
(detail)
|
| |
|
2017 |
Detection of hydrodynamic stimuli by the postcranial body of Florida manatees (Trichechus manatus latirostris).
Jour. Comp. Physiol. A 203: 111–120. 2 tabs. 4 figs. DOI 10.1007/s00359-016-1142-8. Publ. online Feb. 13, 2017.
–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.
|
|
|
Bauer, Gordon B.; Reep, Roger L.; Marshall, Christopher D.
(detail)
|
| |
|
2018 |
The tactile senses of marine mammals.
International Journal of Comparative Psychology 31: 1-28. https://escholarship.org/uc/item/1vk1c9z1
–ABSTRACT: The successful return of mammals to aquatic environments presented numerous sensory challenges to overcome. Aquatic habitats reduced the utility of vision and the type of chemoreception important in terrestrial perception. In several orders, the sense of touch assumed greater importance, especially when enhanced by the development of vibrissal (sensory hair) systems. Species of two extant orders, Sirenia and Cetacea, lost all of their hairs except for vibrissae. In the former, these hairs cover the entire bodies of the two families, Trichechidae and Dugongidae. Hairs in adult cetaceans are more constrained (e.g., some river dolphins and baleen whales) and are restricted primarily to rostral regions. Pinnipeds and sea otters retained their pelage, but in addition have elaborated their mystacial and other facial vibrissae. High numbers of vibrissal receptors, associated dense innervation, prominence of neural tracts, and hypertrophy of brain areas associated with touch suggest an importance of tactile senses for aquatic mammals. Experimental testing has demonstrated the exquisite tactile sensitivity of many marine mammal species. Sensory hairs contribute to that tactile sensitivity in both haptic and mechanosensory contexts. Several, if not most, pinniped species, seals and sea lions, can track prey based on mechanoreception alone. In this review we will discuss the neurobiological and behavioral evidence for the tactile senses of marine mammals.
|
|
Bibliography and Index of the Sirenia and Desmostylia 