212 



Fishery Bulletin 88(1 



1990 



ISl 

 LU 



o 



z 



UJ 

 (T 

 CE 



O 



o 

 o 



70 



60 



50 



40 



30 



20 



10 



Gonad size R * L 



AND 



Meiotic activity R^L 



RELATIVE SIZE AND MEIOTIC ACTIVITY 



Figure 6 



Percentage occurrence of relative level of meiotic activity and relative 

 size of right (R) and left (L) gonads of South Pacific albacore. On 

 the abscissa, upper expression refers to relative gonad size, and lower 

 expression refers to relative level of meiotic activity. 



28 

 26 

 24 

 22 

 20 

 18 

 16 

 14 

 12 

 10 



a 



6 



4 



RIGHT LEFT 

 ROSTRAL 



RIGHT LEFT 

 MEDIAL 



TESTIS SECTION 



RIGHT LEFT 

 CAUDAL 



Figure 7 



Relative abundance of sperm in rostral, medial, and caudal portions 

 of the right and left testes of South Pacific albacore. 



A. 



 J *> 





.• 



-i*'. 



it >t t 



'>^' 





I 





Figure 8 



(A) Empty sperm (iuct of an immature South Pacific albacore; 



(B) sperm duct of a mature albacore filled with sperm. xlOO. 



than for the right testis. The relative abundance of each 

 group of germ cells was highest in the caudal portion 

 and decreased towards the rostral portion in both the 

 left and right testes in all sizes of fish. 



Sperm duct development 



During testicular morjihogenesis, teleost sperm ducts 

 are formed by somatic cells derived from the somatic 

 wall (Nagahama 1983). The main duct is present in im- 

 mature albacore testes (Fig. 8A) in which no sperm are 

 found. In mature albacore, we observed that the sperm 

 duct is located near the center of the testis (Fig. 8B) 

 and that a branching system of tubules radiates toward 

 and end blindly at the testicular periphery. These obser- 



