ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Two nurse sharks (Ginglymostoma cirratum) were trained to respond to the galvanic dipole fields of steel spheres with and without a background electric field. Detection ranges were increased by a factor of 1.6 with background-field-on over background-field-off for dc fields in the range of 0.01 μV/cm to 0.04 μV/cm independent of background field strength. No increase in detection range was found for a background field strength of 0.005 μV/cm. Similar results were obtained for an ac background field of 0.005 μV/cm zero-to-peak at frequencies from 0.2 Hz to 1.6 Hz. These results indicate that threshold sensitivity was increased by a factor of 4 with the background field on. Further observations made on one shark, electric dipoles, and a dc background field of 0.02 μV/ cm, are consistent with the factor of four increase in threshold sensitivity with the background field on found using the steel balls. The reason for the observed increase in sensitivity is unknown.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00610854
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