MYRICK ET AL.: DENTAL LAYERS IN HAWAIIAN SPINNER DOLPHINS 



B 



FIGURE 9.— Comparison of GLG patterns in teeth 

 from dolphin carcass WFP 606 prepared by two 

 methods: A. Untreated thin section (39X). B. De- 

 calcified and stained thin section (39X). 



Pi 



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r 



found in the cementum compared with those in the 

 dentine of the specimens. In the captive-born 

 specimen, WFP 670, with about 25 dentinal labels, 

 the cementum contained only three labels. In 

 specimen WFP 669, only four cemental labels were 

 observed (Fig. 10A) compared with 30 dentinal 

 labels (Fig. 4A). The cementum in the other 

 specimens had either zero or 1 label, despite the 

 numerous dentinal labels observed for each. 



Cemental GLG pattern. — In untreated thin sec- 

 tions, a cemental GLG consisted of a dark layer and a 

 light layer (Fig. 10B). In D/S sections it was com- 

 posed of a dark-stained layer, corresponding to the 

 dark layer in untreated sections, and a lightly stained 

 layer (Fig. 1 1). In both types of preparations, the dark 



layers contained larger concentrations of ceraen- 

 tocytes than did the light layers. 



Calibration of cemental GLGs. — Calibrations of 

 cemental GLGs with those in the dentine were car- 

 ried out using the assumption that cementum is a less 

 sensitive recording structure than dentine (Klevezal' 

 1980) and that labels occurring in the cementum cor- 

 responded only to the brightest and thickest labels or 

 label groups in the dentine. Thus, for example, the 

 four labels detected in the cementum of specimen 

 WFP 669 (Fig. 10A) were flagged with the same let- 

 ters used to identify multiple label concentrations in 

 the dentine (Fig. 4A). 



In some cases, such as in WFP 669, plastic overlays 

 were used to determine that a cemental GLG rep- 



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