The Role of Magnetic Statoconia in Dogfish (Squalus Acanthias)

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Abstract
Mineralogical and magnetic properties of the otolithic mass in the sacculus of dogfish, Squalus acanthias, were investigated. The endogenous statoconia were found to be either rhombohedral crystals of calcite or spherical particles of other calcium carbonate polymorphs. From 20 to 60% of the total otolithic mass consisted of exogenous material, sea sand, which had a high content of heavy mineral particles, some of which were magnetic. The concentration of the heavy particles was greater than that typically found in marine sand, and it is proposed that this could result from a separation process in the endolymphatic duct.A calculation of the acceleration of the otolithic mass in the sacculus caused by the geomagnetic field showed that the maximum linear acceleration due to magnetic forces would be one or two orders of magnitude smaller than the minimum sensitivity to acceleration in the auditory frequency range. This makes it unlikely that the magnetic particles are involved in detection of the geomagnetic field.The exogenous material raises the mass and density of the otolithic mass in the sacculus, thus increasing the sensitivity of this otolith organ.

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