The long axes of aragonite fibrils (level 2), which are about 1.5 mm in length
(Fig. 6.6d), are arranged along x-direction; the layers (level 3) accumulate along
z-direction and extend along y-direction. The three directions are vertical to each
other and form the three-dimensional sticklike structure. The long axis of the stick
which is tens of microns in length is along y-direction.
Level 5: the domain structure
Based on the investigations of the morphology in a single ring structure, it is
proposed that there exists a domain structure of the stick (level 4) orientation in the
lapillus. Within micron range, hundreds of sticks appear to be arranged at the same
orientation and make up the domain structure. The black circle whose diameter is
about 100 mm in Fig. 6.6e is the area of a domain and the arrow shows the direction
of the sticks’ arrangement.
Level 6: the domain arrays
Level 6 pattern is essentially the combination of Level 5 structure into hundreds
of microns and even millimeter scale. All these domains appear in the same ring.
Level 6 structure represents one daily increment. According to Fig. 6.6f, the long
axis direction of the stick is not inside the daily increment layer and most of the
neighboring domains have the similar direction.
Level 7: the daily increments
The daily ring structure is shown in Fig. 6.6g. The width of each daily increment
(the transparent area in the pattern) is between 1 and 2 mm and the absent area is the
proteins which were etched. Figure 6.6h is the digital camera photograph of a pair
of lapilli.
6.2.1.2 Hierarchical Structure of Sagitta
The aragonite crystals of a sagitta have the same structure of level 1 as a lapillus
(Fig. 6.7a). The hierarchical structure of a sagitta is much more simple than that of a
lapillus. Figure 6.7b shows the transect of single increment where we can distinguish clearly the aragonite fibril, which is about 1.5 mm in length and 250 nm in
diameter (level 2). The aragonite fibrils in sagitta are larger than those in lapillus,
but sagitta has not as many multilevels as lapillus. The aragonite fibrils are the
direct building blocks for the daily increment and the direction of the fibrils is
vertical to the daily increment layers (Fig. 6.7c). Figure 6.7d shows clearly the daily
growth structure of sagitta. Because the core is not in the center of the transect, the
width in different parts of the same daily increment is quite different. Figure 6.7e is
a schematic illustration of the daily increment structure of a sagitta which has only
one core (sometimes there are two or three cores in the otolith). Figure 6.7f is the
digital camera photograph of a whole sagitta.
Fig. 6.6 (continued) structure, (e) Level 5: SEM micrograph of an orientation domain, (f) Level 6:
SEM micrograph of interior structure of a daily increment, (g) Level 7: SEM micrograph of daily
increments, bar ¼ 10 mm, and (h) digital camera graph of the lapillus, bar ¼ 5 mm
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Q. Feng
(Fig. 6.6d), are arranged along x-direction; the layers (level 3) accumulate along
z-direction and extend along y-direction. The three directions are vertical to each
other and form the three-dimensional sticklike structure. The long axis of the stick
which is tens of microns in length is along y-direction.
Level 5: the domain structure
Based on the investigations of the morphology in a single ring structure, it is
proposed that there exists a domain structure of the stick (level 4) orientation in the
lapillus. Within micron range, hundreds of sticks appear to be arranged at the same
orientation and make up the domain structure. The black circle whose diameter is
about 100 mm in Fig. 6.6e is the area of a domain and the arrow shows the direction
of the sticks’ arrangement.
Level 6: the domain arrays
Level 6 pattern is essentially the combination of Level 5 structure into hundreds
of microns and even millimeter scale. All these domains appear in the same ring.
Level 6 structure represents one daily increment. According to Fig. 6.6f, the long
axis direction of the stick is not inside the daily increment layer and most of the
neighboring domains have the similar direction.
Level 7: the daily increments
The daily ring structure is shown in Fig. 6.6g. The width of each daily increment
(the transparent area in the pattern) is between 1 and 2 mm and the absent area is the
proteins which were etched. Figure 6.6h is the digital camera photograph of a pair
of lapilli.
6.2.1.2 Hierarchical Structure of Sagitta
The aragonite crystals of a sagitta have the same structure of level 1 as a lapillus
(Fig. 6.7a). The hierarchical structure of a sagitta is much more simple than that of a
lapillus. Figure 6.7b shows the transect of single increment where we can distinguish clearly the aragonite fibril, which is about 1.5 mm in length and 250 nm in
diameter (level 2). The aragonite fibrils in sagitta are larger than those in lapillus,
but sagitta has not as many multilevels as lapillus. The aragonite fibrils are the
direct building blocks for the daily increment and the direction of the fibrils is
vertical to the daily increment layers (Fig. 6.7c). Figure 6.7d shows clearly the daily
growth structure of sagitta. Because the core is not in the center of the transect, the
width in different parts of the same daily increment is quite different. Figure 6.7e is
a schematic illustration of the daily increment structure of a sagitta which has only
one core (sometimes there are two or three cores in the otolith). Figure 6.7f is the
digital camera photograph of a whole sagitta.
Fig. 6.6 (continued) structure, (e) Level 5: SEM micrograph of an orientation domain, (f) Level 6:
SEM micrograph of interior structure of a daily increment, (g) Level 7: SEM micrograph of daily
increments, bar ¼ 10 mm, and (h) digital camera graph of the lapillus, bar ¼ 5 mm
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156
Q. Feng