Zusammenfassung Es wurde erstmals für Echinodermen primär polykristalliner Calcit nachgewiesen, und zwar im Cortex der Primärstacheln der Cidaridae, dem sekundären Zahnskelet von Clypeaster und in den akzessorischen Kalkstrukturen, die im Kauabschnitt die Furche der Diadematiden-Zähne ausfüllen. Es gibt bei anderen Seeigelfamilien keine Bildungen, die dem Cidariden-Cortex oder den akzessorischen Kalkstrukturen der Diadematiden homolog sind. Das polykristalline sekundäre Zahnskelet von Clypeaster ist dagegen dem monokristallinen sekundären Zahnskelet anderer Seeigel homolog.Der Mg-Gehalt des Calcits liegt in den feinkristallinen Zonen (mit Ausnahme des Cortex) im allgemeinen höher; die höchsten Werte finden sich in den Steinteilen der Zähne, gleichgültig ob das sekundäre Zahnskelet mono- oder polykristallin ist.Polykristalline Teile sind im allgemeinen härter als monokristalline Teile. Die Steinteile der Seeigelzähne sind die härtesten Skeletteile von Echinodermen überhaupt; ihre VickersHärte übertrifft weit diejenige von solidem Calcit. Im Steinteil ist das feinkristalline Gefüge von Calcit eng mit organischer Matrix verbunden, und es wird vermutet, daß darauf die besonders hohe Härte der Steinteile beruht.
Polycristalline calcite in sea urchins
Summary For the first time primary polycrystalline calcite in Echinoderms is shown in the cortex of primary spines of Cidaridae, in the secondary tooth skeleton of Clypeaster and in the accessory calcareous structures filling the crevice fold in the chewing areas of Diadematoidae teeth. Other Echinoid families lack formations homologous to the cortex of Cidaridae and accessory calcareous structures of Diadematoidae. On the other hand the polycrystalline secondary tooth skeleton of Clypeaster is homologous to the monocrystalline one of the other sea urchins.With the exception of cortex the Mg-content in calcite—analyzed by microprobe and X-ray powder method—is generally greater in macrocrystalline parts. The highest Mg-contents are found in the stone parts of teeth irrespective of whether the secondary tooth skeleton is monocrystalline or polycrystalline.Polycrystalline parts are usually harder than monocrystalline ones. The stone parts of Echinoid teeth are the hardest skeleton parts of Echinoderms on the whole; their hardness is much greater than that of solid calcite. It is supposed that the strong interlacing of the microcrystalline calcite and organic matter causes the enormous hardness of the stone part.
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft. 相似文献
Within the framework of the Sicily Mummy Project, the orofacial complex of a significant sample of individuals (n = 111) from the Capuchin Catacombs of Palermo, Italy, was inspected. The heads and dentitions of the mummies were documented and the recorded findings described: the state of preservation of skeletal and soft tissues; dental pathologies such as carious lesions and alveolar bone loss; enamel hypoplasia; and ante- and post-mortem tooth loss. Despite limitations in data collection, the oral health of these mummies was assessed and the frequencies of pathologies were compared to those of similar populations. From their position within the corridors of the Catacombs, sex and social status of the mummies were also inferred, allowing the dental pathologies to be specified in the social and historical context. Most interestingly, the rate of oral health problems did not differ between the groups of the members of the Capuchin Order and the laymen of the city of Palermo, despite their different lifestyles. 相似文献
Teeth resection is a method of controlling the injurious effects of the aggression displayed when newborn piglets fight to establish a teat order. Recent European legislation discourages the practice. The objective of this study was to assess the effect of clipping and grinding piglets’ needle teeth, compared to leaving them intact, on the welfare of piglets in farrowing crates.
Six days pre-partum, 60 sows were assigned to one of three treatments. Litters had their teeth clipped (C), ground (G) or left intact (I) at birth. The time taken to carry out each procedure was recorded. Piglet weights and facial lesions, which were scored according to severity, were recorded on days 1, 4, 11, 18 and 27. Piglet weights were also recorded at birth. Mouth lesions were recorded on days 1, 4 and 27. Instantaneous scan samples of piglet behaviour were carried out for 30 min post-teeth resection procedure (1 min intervals), and for 6 h on days 1, 4, 8, 14, 21 and 26 (5 min intervals). One male and one female piglet per litter were chosen as focal animals and observed for 5 min each post-procedure and for 10 min each twice per day on days 1, 5, 12, 20 and 26. Mortalities were recorded throughout lactation.
Grinding took significantly longer than clipping the teeth or leaving them intact (F = 638.87, P < 0.001). I piglets had higher facial lesion scores than C and G piglets (F = 10.58, P < 0.001). A smaller proportion of piglets in I litters than C and G litters and a smaller proportion of piglets in G litters than C litters had at least one mouth lesion (F = 4.74, P < 0.001). During 30 min post-procedure, I piglets were active on the heatpad in more observations than C and G piglets (F = 3.49, P < 0.05). During 5 min post-procedure C piglets spent longer chomping than I piglets (F = 5.92, P = 0.05). On day 21, I piglets were active in more observations than G piglets (F = 2.11, P < 0.05). On day 26, G piglets were inactive in more observations than C and I piglets (F = 5.02, P < 0.05). On days 14 and 26, C piglets were sleeping in more observations than G piglets (F = 2.87, P = 0.05). There was a tendency for a larger proportion of I than C piglets to die due to overlying (F = 2.68, P = 0.08).
In conclusion, although all three options were associated with welfare problems, grinding can be recommended in preference to clipping or leaving the teeth intact. 相似文献
This study employs dental microwear texture analysis to reconstruct the diets of two families of subfossil lemurs from Madagascar, the archaeolemurids and megaladapids. This technique is based on three-dimensional surface measurements utilizing a white-light confocal profiler and scale-sensitive fractal analysis. Data were recorded for six texture variables previously used successfully to distinguish between living primates with known dietary differences. Statistical analyses revealed that the archaeolemurids and megaladapids have overlapping microwear texture signatures, suggesting that the two families occasionally depended on resources with similar mechanical properties. Even so, moderate variation in most attributes is evident, and results suggest potential differences in the foods consumed by the two families. The microwear pattern for the megaladapids indicates a preference for tougher foods, such as many leaves, while that of the archaeolemurids is consistent with the consumption of harder foods. The results also indicate some intraspecific differences among taxa within each family. This evidence suggests that the archaeolemurids and megaladapids, like many living primates, likely consumed a variety of food types. 相似文献
We investigated the state of dental eruption in specimens of Macroscelides proboscideus and Erinaceus europaeus of known age. When M. proboscideus reaches adult size and sexual maturity, few or none of its replaced permanent cheek teeth have erupted. The approximate sequence
of upper tooth eruption is P1, [I3, C, M1], [I1–2], M2, P4, [P2, P3]. Chronologically, E. europaeus erupts its molars and most premolars prior to M. proboscideus; but its first two upper incisors erupt after those of M. proboscideus, and its canines erupt around the same time. The approximate sequence of upper tooth eruption in E. europaeus is [M1, M2, P2, I3], C, M3, P4, P3, I2, I1. Unlike M. proboscideus, E. europaeus does not reach adult size until all permanent teeth except for the anterior incisors have erupted. While not unique among
mammals, the attainment of adult body size prior to complete eruption of the permanent cheek teeth is particularly common
among macroscelidids and other afrotherians. 相似文献