Peres and Vooren: Sexual maturation, reproductive cycle, and fecundity of Oaleorhinus galeus 



663 



The HSI of adult females varied during the 

 reproductive cycle; the mean was 7.2 in GR 

 females, 10.8 in NGR-1, and 17.2 in NGR-2 fe- 

 males (Fig. 13). In all categories, the mean 

 monthly HSI decreased from a maximum in early 

 winter to a minimum in spring (Fig. 14). 



Discussion 



Body size at attainment of sexual maturity, as a 

 percent of maximum size, and the slope of the 

 linear regression of fecundity on total length are 

 similar in the western South Atlantic, Australian, 

 and eastern North Pacific populations of the 

 school shark (Table 3, Fig. 15). It is concluded that 

 these parameters of reproduction are characters 

 at the species level. 



The dense groups of spermatozoa in the seminal 

 vesicles of adult males of the school shark were 

 designated spermatophores, in 

 analogy with structures de- 

 scribed in the basking shark Ceto- 

 rhinus maximus and the blue 

 shark Prionace glauca (Mat- 

 thews 1950, Pratt 1979). During 

 the present study, spermato- 

 phores were also found in the 

 seminal vesicle of the smooth 

 dogfish Mustelus canis and the 

 sand shark Eugomphodm taunts. 

 It seems that the grouping of 

 spermatozoa in dense agglomera- 

 tions is a commom feature in 

 elasmobranchs. 



There is no discontinuity in the 

 gonadosomatic index of school 

 shark adult males, such as would 

 indicate the simultaneous exis- 

 tence of different reproductive 

 stages, as was observed in fe- 

 males. All smears of the seminal 

 vesicle of adult males in July con- 

 tained spermatophores. It is con- 

 cluded that all adult males pres- 

 ent in the area during winter are 

 in the mating stage. 



In the western South Atlantic 

 population, copulation occurs up 

 to at least 5 months before ovula- 

 tion. Gestation is highly synchro- 

 nized, with all phases from ovula- 

 tion to birth being timed at the population level. This 

 requires that at a particular period each year, all NGR-2 



females will have mated and will be ready to ovulate. 



The extended mating period ensures this. The same is 

 observed in the blue shark, where the female mates up 

 to 12 months before ovulation (Pratt 1979). 



