PRATT REPRODUCTION IN BLUE SHARKS 



vagina during copulation. The siphon sacs origi- 

 nate on the surface of the pelvic fin at the proximal 

 end of the clasper and extend anteriorly under the 

 dermis to end blindly just short of the pectoral 

 girdle. They are approximately 25 mm in diameter 

 and 60 cm long. 



Spermatoza 



Sperm cells (Figure 5) develop in expendable 

 spheres of germinal tissue, the seminiferous am- 

 pullae described by Romer (1962). They form ra- 

 dially, then clump together in groups of 60-70 (Fig- 

 ure 6). When the sperm mature the ampullae 

 disintegrate, liberating individual spermatozoa 

 into the interstitial spaces of the testis. They pass 

 through the ductus efferens (Figure 2) and into the 

 epididymis. Secretions from the accessory glands 

 flow into the epididymis and form a matrix which 

 supports the individual spermatozoa. Sper- 

 matozoa are stored in the epididymis which usu- 

 ally appears swollen in adult males. This is the 

 most convenient location to obtain a sperm smear. 

 In the lower epididymis the spermatozoa again 

 aggregate, with heads aligned parallel until 



groups of 60-70 are formed in the anterior section 

 of the ductus deferens. Hundreds of these packets 

 then aggregate into spermatophores (Figure 7), 

 which are stored in the expanded terminal am- 

 pulla of the ductus deferens. 



Spermatophores 



In mature males the entire lumen of the lower 

 ductus deferens is usually turgid with seminal 

 products. Most noticeable macroscopically are 

 snow-white clumps of a gelatinous substance 3-4 

 mm in diameter and containing no spermatozoa. 

 This evidently is a supportive and possibly nutri- 

 tive material for the smaller spermatophores. The 

 blue shark spermatophore (Figure 7) is an ivory 

 white ovoid, 0.5-2.0 mm across its largest diame- 

 ter. When the ampulla is cut at midkidney, sper- 

 matophores flow freely and copiously from the 

 incision and are interspersed with the white gel- 

 atinous clumps. Several hundred milliliters may 

 be expressed from the two ductus deferens of an 

 adult male. 



Matthews (1950) gave a good account of the 

 structures and functions involved in spermato- 



FIGURE 6. — Spermatozoa in seminifer- 

 ous ampullae of the blue shark 

 (X 1,600). 



449 



