Larval cichlid fish (Oreochromis mossambicus) were kept at hypergravity (hg; centrifuge) for 6 h. Following the transfer to 1 g (i.e. stopping the centrifuge), animals were separated into normally and abnormally (kinetotic) swimming individuals (the latter were swimming kinetotically, i.e. performing spinning movements). Subsequently, carbonic anhydrase- (CA-) reactivity was histochemically demonstrated and densitometrically determined in inner ear maculae. It was found that both the total macular CA-reactivity as well as the difference in reactivates between left and right maculae were significantly lower in normally swimming hg-animals as compared to the kinetotically behaving hg-fish (P<0.0001). This result is in complete agreement with closely related studies carried out on the calcium incorporation of inner ear otoliths and indicates that a regulatory mechanism, which adjusts otolithic calcium carbonate incorporation towards the gravity vector, acts via activation/deactivation of macular CA.

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http://dx.doi.org/10.1016/s0304-3940(02)01151-5DOI Listing

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