FISHERY BULLETIN: VOL. 86, NO. 3 



Figure 3e.— A laminar pattern of crystalline growth on the medial face of the irregular lobe. Scale bar = 10 fxm. 



edge of this lobe, a laminar crystalline growth pat- 

 tern develops, adding to the overall variation of 

 crystal structures on the medial surface (Fig. 3e). 

 Other studies of otolith ultrastructure present the 

 otolith as homogeneous in crystal form, composed 

 almost entirely of monoclinal aragonite crystals 

 (Degens et al. 1969). The complex crystallinity of 

 the oreo otoliths resembles that of the mollusc shell, 

 v^hich, although aragonitic, often has a pattern of 

 complex variation in crystal habit (Carriker et al. 

 1980). 



Within the broken otolith, the nucleus lies at the 

 center of a spherical primordium (Fig. 4a). Crystals 

 grow outwards from the primordium and epitaxial 

 (Degens 1976) growth patterns exist (Fig. 4b). Com- 

 plex leaf-shaped crystals occur in areas directly 

 beneath the lateral surface of the fractured irregular 

 lobe (Fig. 4c). Beneath the medial surface, a remark- 

 able series of hexogonal crystals of calcite occur as 

 large rectangular blocks embedded within the 

 otolith (Fig. 4d). Calcitic prisms have been described 

 in molluscs as resulting from the regeneration of 

 broken shells (Watabe 1983). It is difficult to imagine 

 otoliths being broken and regenerated in situ. 



Major and minor check rings similar to those 



described (Gaul die 1987) for otoliths from the orange 

 roughy, a deepwater species from the same habitat, 

 occur (Fig. 4e). When polished and etched, the check 

 rings become clearly visible with deep etched checks 

 occurring between the less deeply etched checks 

 analagous to microscopic growth increments in 

 other species (Fig. 4f). At a higher magnification the 

 finer increments become obscured by the coarseness 

 of the underlying crystal type (Fig. 4g). Those fine 

 increments that are visible occur irregularly and 

 have varying widths. 



Large-scale rings analogous to opaque/hyaline an- 

 nual zones were observed in the regular lobe. The 

 mean width of these zones, measured using 

 transmitted light (Fig. lb), was 0.34 mm (±0.06). 

 The concentric ridges observed by SEM on the 

 lateral surface of the regular lobe (Fig. Ic) have a 

 mean width of 0.27 mm (±0.06). These two struc- 

 tures, opaque/hyaline zones and surface ridges, have 

 about the same width with no statistically signifi- 

 cant differences between them. 



Examination of otolith cross sections reveals 

 widely spaced, large rings with many finer rings in 

 between (Fig. 4h). When examined in greater detail, 

 the demarcation between the large and finer rings 



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