Figure 7. — Spermatophore of the blue 

 shark (xlOO). 







FISHERY BULLETIN: VOL. 77. NO- 2 



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phore formation in the basking shark. He specu- 

 lated that spermatophores preserve the sperm 

 from loss in leakage to the surrounding water dur- 

 ing copulation. Blue shark spermatophores break 

 down in seawater, liberating individual sper- 

 matozoa, so rapid transfer is necessary. The sper- 

 matophore may simply be an efficient way to store 

 spermatozoa in the male's ductus deferens. 



Indicators of Sexual Maturity in Males 



The simplest technique to determine maturity 

 is to compare external secondary sexually dimor- 

 phic characteristics that occur in large animals 

 with those same characters as they appear in less 

 developed members of the species. In male elas- 

 mobranchs changes in relative size, hardness, and 

 development of the claspers is the most frequently 



4,50 



employed method for determining sexual matur- 

 ity. Clark and von Schmidt (1965) considered a 

 male mature when: 1) the distal end of the clasper 

 and rhipidion are fully formed and can be spread 

 open on a fresh specimen, 2) the clasper proximal 

 to the head is rigid due to calcification of the sup- 

 porting cartilage, 3) the base of the clasper rotates 

 easily and the clasper can be directed anteriorly, 

 and 4) the siphon sacs are fully elongated. Aasen 

 (1966, footnote 5) used clasper length exclusively 

 as a maturity index in his work on blue and por- 

 beagle sharks. Springer (1960) noted that the 

 claspers of the sandbar shark become hardened or 

 calcified at about the same time that the testes 

 enlarge. 



^Aasen. O. 1961. Some observations on the biology of the 

 porbeagle sharkLamna nasus. Bonnaterre. Int. Counc. Kxplor. 

 Sea, CM. 1961, 109:1-7. 



