The pathological alterations of enamel structure in the teeth of wild boars from fluoride polluted areas in N-Bohemia (Czech Republic) and S-Saxony (Germany) were studied on a macroscopic and a microscopic level. Mandibular bone fluoride concentration (mg F Ϫ /kg, dry wt; mean Ϯ SD, individuals Ͻ24 months of age) in the specimens from N-Bohemia (754.3 Ϯ 149.6) and S-Saxony (490.8 Ϯ 135.1) was significantly higher than that of controls (free of dental fluorosis), originating from the western part of Germany (304.7 Ϯ 91.0). Fluoride content in bulk enamel (mg F Ϫ /kg, ash wt) of fluorotic permanent teeth from N-Bohemia (382.1 Ϯ 165.2) and S-Saxony (125.0 Ϯ 38.3) was likewise significantly increased over that of non-fluorotic control teeth from W-Germany (33.6 Ϯ 26.7). Macroscopically, fluorosed wild boar enamel exhibited opacity and discoloration of varying extent, accentuated perikymata as well as hypoplastic and posteruptive surface defects. Microradiographic and scanning electron microscopic analyses revealed enamel subsurface hypomineralization, accentuated Retzius lines and occurrence of broad, hypomineralized incremental bands of abnormal structure underlying hypoplastic enamel surface defects. The presence of zones of aprismatic enamel was associated with these bands. Incremental bands with altered enamel structure and enamel surface hypoplasias, both denoting a severe disturbance during the secretory stage of amelogenesis, have previously been observed in rodents following acute parenteral fluoride dosing. It is concluded that in the chronically fluoride exposed wild boars periods of especially elevated plasma fluoride levels exerted an acute toxic effect on the secretory ameloblasts. A feature not previously reported from fluorosed enamel was the occurrence of canal-like structures that originated at the broad incremental bands and extended into the external enamel. The presence of these canals presumably results from a delay in the resumption of secretory activity by groups of ameloblasts following a fluoride insult. Based on experimental evidence in domestic pigs and in sheep, the overall subsurface hypomineralization of fluorosed wild boar enamel is attributed to a disturbance of enamel maturation. The distribution of fluorotic enamel changes within the dentition of the wild boars could be related to the developmental sequence of tooth formation in the species. Teeth whose crown formation took place prenatally (deciduous teeth) or largely pre-weaning (permanent first molars) exhibited no or only moderate fluorotic enamel alterations. Based on the extension of enamel surface hypoplasias along the coronoapical axes of the tooth crowns, the timing of excess fluoride exposure that caused a marked disruption of enamel matrix secretion was estimated in specimens with a known date of death. The results indicate that the wild boars had been exposed to a particularly severe fluoride impact during autumn and winter of their first year of life. Anat Rec 259:12-24, 2000.

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SUMMARYEvidence for magnetoreception in mammals remains limited. Magnetic compass orientation or magnetic alignment has been conclusively demonstrated in only a handful of mammalian species. The functional properties and underlying mechanisms have been most thoroughly characterized in Ansellʼs mole-rat, Fukomys anselli, which is the species of choice due to its spontaneous drive to construct nests in the southeastern sector of a circular arena using the magnetic field azimuth as the primary orientation cue. Because of the remarkable consistency between experiments, it is generally believed that this directional preference is innate. To test the hypothesis that spontaneous southeastern directional preference is a shared, ancestral feature of all African mole-rats (Bathyergidae, Rodentia), we employed the same arena assay to study magnetic orientation in two other mole-rat species, the social giant mole-rat, Fukomys mechowii, and the solitary silvery mole-rat, Heliophobius argenteocinereus. Both species exhibited spontaneous western directional preference and deflected their directional preference according to shifts in the direction of magnetic north, clearly indicating that they were deriving directional information from the magnetic field. Because all of the experiments were performed in total darkness, our results strongly suggest that all African mole-rats use a lightindependent magnetic compass for near-space orientation. However, the spontaneous directional preference is not common and may be either innate (but species-specific) or learned. We propose an experiment that should be performed to distinguish between these two alternatives.Supplementary material available online at