PRATT REPRODUCTION IN BLUE SHARKS 



diameter, the seminiferous ampullae (Figure 3). 

 The only other macroscopic structures are suppor- 

 tive partitions of connective tissue radiating in- 

 ternally from a band on the mediolateral surface of 

 the testes. A double mesorchia suspends the testes 

 from the midline of the dorsal body wall. The duc- 

 tus efferens is a series of fine tubules which crosses 

 the mesorchium at its anterior edge and com- 

 municates with the head of the epididymis. 



Epididymis 



Above the testes on the dorsal abdominal wall 

 lie the paired epididymides. They are attached on 

 either side of the dorsal aorta in the hollow of the 

 ventrolateral processes of the vertebral column. In 

 the adult blue shark the epididymis is approxi- 

 mately 3 cm wide, 30 cm long, and 0.5 cm thick. In 

 sharks captured from March to November it is 

 turgid with spermatozoa in a matrix of supportive 

 tissue secreted by accessory glands on the dorsal 

 surface. The epididymis originates just forward of 

 and adjacent to the testes as a firm subspherical 

 "head" which narrows to a short "neck" and then 

 expands to form a long straplike organ (Figure 2). 

 The tubules of this organ describe a path of con- 

 volutions so complex that its surface appears cere- 

 briform. Tubule diameters range from 1.5 to 1.75 

 mm adjacent to the testes, expanding to >2 mm at 



the junction of the ductus deferens. Here it enters 

 Leydig's gland, the modified anterior section of the 

 mesonephric kidney. At this level the function of 

 the ductus changes from spermatozoa storage to 

 spermatophore formation and storage. 



Ductus Dctcrens 



The ductus deferens (Figure 4) is the storage 

 organ for male seminal products. The ductus 

 gradually increases in diameter as it penetrates 

 the kidney, finally enlarging in strong convolu- 

 tions to form the ampulla ductus deferens which is 

 10-15 mm in diameter in the adult blue shark. The 

 ampullae are lined with partitions or septa similar 

 to those noted by Matthews ( 1950) in the basking 

 shark, Cetorhtnus maximus. The thin-walled ure- 

 ter becomes entwined with the ductus deferens in 

 the last 20 cm of its length and roughly parallels 

 its sinuous course. The ureter and ductus deferens 

 terminate in a common double papilla which pro- 

 jects into the anterior wall of the urogenital sinus. 

 The ductus occupies the central orifice of the 

 papilla and is closed by a sphincter muscle. The 

 ureter has a crescent-shaped sphincterless duct on 

 the dorsal edge of the cone of the papilla. The 

 urogenital sinus vents into the common cloaca by 

 means of a single large (2 cm) papilla that projects 

 from the dorsal bodv wall. 



^ 



^s^' 



Figure 3. — Seminiferous ampullae of 

 mature testes in the blue shark ( ■< 160). 

 Spermatozoa arranged radially inside 

 spheres (seen in cross section). 



vx„.--- 





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447 



