GRAHAM: HEAT EXCHANGE IN SCOMBRIDS 



Figure 2.-Central heat exchanger of 

 Thunnus albacares. (Top right, scale 

 = 6.5 cm): Transverse sections show- 

 ing the position of red muscle (rm) 

 and the central heat exchanger (che). 

 (Top left, scale = 1.5 cm): Transverse 

 section of the che showing the dorsal 

 aorta (da), posterior cardinal vein 

 (pcv), and retia (r). (Middle right, scale 

 = 2 cm): A close view of the che 

 showing the da, pcv, and two wing- 

 shaped retia that proceed supra- 

 laterally from the vessels. (Middle 

 left, scale = 1.2 cm): A ventrolateral 

 view of the da, pcv, and the sheet of 

 vessels (v) outside the haemal arch 

 that penetrate red muscle. (Bottom, 

 scale = 2.0 cm): Ventrolateral view 

 showing the che on the left and the 

 thin sheet of vessels in red muscle. 



hypaxial and epaxial red muscle reach the ver- 

 tebrae. Longitudinally, shape as well as thickness 

 of red muscle varies at different points (cf. 

 Kishinouye 1923, Plate XVII). Generally, red 

 muscle in K. pelamis appears to have more 



ligaments than T. albacares. In both species the 

 myomeres are continuous through red and white 

 muscle (Figures 2, 3), but red and white muscle are 

 easily distinguished and separate with slight 

 teasing. 



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