Ferreira and Vooren: Age, growth, and structure of vertebra in Galeorhmus galeus 



25 



Figure 10 



Sagittal section of Gnleorhinus galeus 

 vertebra showing contrasting tissue 

 of cone and intermedialia. (Harris's 

 haematoxylin, lOOx) 



Figure 1 1 



Section of vertebral tissue of Gale- 

 orhinus galeus showing the thin chan- 

 nels linking the cells. (Harris's 

 haematoxylin, 400 x) 



Thin vascular channels connecting the cartilage cells 

 were observed in haematoxylin-stained sections of 

 resin-embedded vertebrae. These canaliculi form a net- 

 work in the matrix between cells providing an oppor- 

 tunity for fluids and nutrients to reach the interior from 

 the external medium (Fig. 11). Absence of lipid inclu- 

 sions in the chondrocytes is interpreted as evidence of 

 a healthy and active cellular metabolism. The presence 



of isogenic groups of cells suggests that cells divide in- 

 terstitially and thus effect interstitial growth. 



The widths of translucent and opaque zones varied 

 in individuals. Rings were usually narrower than adja- 

 cent opaque zones, but with increased body size (TL), 

 both attained the same average size (Figs. 12, 13). 

 Width of a male's opaque zones decreases gradually, 

 and after about the 15th ring the two zones are equal 



