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Reep, Roger Lyons; Gaspard, Joseph C., III; Sarko, Diana K.; Rice, Frank L.; Mann, David A.; Bauer, Gordon B.
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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.
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Sarko, Diana K.; Rice, Frank L.; Reep, Roger Lyons
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2011 |
Mammalian tactile hair: divergence from a limited distribution.
Annals of the New York Academy of Sciences 1225: 90-100. 4 figs. DOI:10.1111/j.1749-6632.2011.05979.x. Apr. 2011.
–ABSTRACT: Mammalian species use tactile hairs to address a variety of perceptual challenges in detecting and responding appropriately to environmental stimuli. With a wide range of functional roles that range from object detection, to fine texture discrimination, to hydrodynamic trail perception, tactile hairs have been adapted for a variety of environmental niches to enhance survival through optimizing detection of somatosensory cues. Because the high level of innervation associated with tactile hairs requires a commensurately high dedication of neural resources, their distribution is restricted to specific regions of the body that encounter stimuli of interest--commonly, the face. However, several species--namely bats, naked mole-rats, hyraxes, manatees, and dugongs--are rare exceptions, with tactile hair distribution that has expanded to cover the entire body. This review examines the behavioral advantages conferred by this unusual trait, the neuroanatomical adaptations that accompany it, and how this pattern might have evolved.
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Bibliography and Index of the Sirenia and Desmostylia 