Abascal et al.: Testicular development in Thunnus thynnus 



411 



L , tf K *.T<£W*. »5r * .'50 ufk 



Figure 4 



Spermatocysts in the testis proliferative region of bluefin tuna (Thunnus thynnus) from Barbate 

 (A and B) and the Balearic Islands (C and D). All stages of spermatogenesis are present in both 

 cases, although spermatid cysts containing late spermatids and spermatozoa (asterisks) are 

 somewhat more abundant in specimens from the Balearic Islands. Arrow = dividing sperma- 

 tocytes; sc = spermatocytes; sd = spermatids; sg = primary spermatogonion; sz = spermatozoa. 

 Plastic-embedded sections (A-D) were stained with toluidine blue. 



germ cell line were present in the gonads. In addition, 

 large amounts of spermatozoa had accumulated in the 

 central system of ducts and in the main sperm duct, 

 both of which appear to function as reservoirs of sperm. 

 In specimens from Barbate, spermatocytes and sper- 



matids were abundant (Fig. 4B), whereas in most tuna 

 collected in the Balearic area spermatids predominated 

 over spermatocytes. Cysts containing late spermatids 

 and spermatozoa were particularly common (Fig. 4, C 

 and D). 



