I'KATT REPRODUCTION IN BLUE SHARKS 



Figure n. — Skm thickness compari- 

 son, cross sections of pelvic region of 

 similar-sized male (left) and female 

 (right) blue shark. 



that insemination is not always accompanied by 

 internal lesions. 



Hermaphroditic Blue Sharks 



Hermaphroditic blue sharks have not been 

 mentioned in the literature and are apparently as 

 rare as in other species of elasmobranchs. The only 

 hermaphroditic blue shark I have examined was 

 caught off central Long Island, 14 July 1973. It 

 was 192 cm long and weighed 94 lb. There were 

 many severe dermal lacerations (mating scars), 

 some so recent as to be freshly clotted. There were 

 two similar-sized claspers on the inner margin of 

 the pelvic fins. They were much too short for the 

 body length (17 mm from the margin of the fin to 

 the free tip) and were not calcified. Internally, a 

 small patch of ovary bearing four large (11 mm) 

 ovarian follicles was found in the normal position 

 on the epigonal organ. All of the reproductive or- 

 gans were reduced; the upper oviduct diameter 

 was 4 mm. Paired oviducal glands were present as 

 10 mm swellings in the oviducts. Caudally the 4 

 mm oviduct expanded to a 10 mm uterus. Two 

 small testes were suspended in the usual position 

 forward in the abdominal cavity. Histological sec- 

 tions revealed spermatozoa in the seminiferous 

 ampullae of the testes. The epididymis and vas 

 deferens were identifiable as undeveloped white 

 tubes 1 mm in diameter. Judging from mating 

 scars on the dorsal surface, this fish was treated by 

 at least some of its conspecifics as a female. Al- 

 though the ovary and testes were developed, the 

 oviduct, ductus deferens, and claspers were too 

 underdeveloped to permit this specimen to be 

 functionallv mature as either a male or female. 



Indicators of Sexual Maturity in Females 



Nearly every structure of the female reproduc- 

 tive tract has been used in the past to determine 

 sexual maturity. Most authors rely on a combina- 

 tion of indicators that account for several stages in 

 the reproductive cycle. Bonham et al. ( 1949) noted 

 that the length of the ovary increased only slightly 

 faster than did the body length of Squaliis acan- 

 thias. Springer (1960) and Kauffman (1950) used 

 the appearance of the elasmobranch ovary as an 

 indicator of maturity. The development of the 

 oviduct has been considered an index by Springer 

 (1960) and Olsen (1954); the oviducal gland by 

 Olsen (1954) and Nalini (1940); and the uterus by 

 Olsen (1954), Templeman (1944), and Aasen (see 

 footnote 5). In the carcharhinids studied by Clark 

 and von Schmidt (1965), the development of the 

 vaginal opening proved to be the most useful ex- 

 ternal indicator of maturity. In young carchar- 

 hinids the vaginal opening begins as a slit in the 

 urinary papilla. 



Defining sexual maturity in female blue sharks 

 is difficult because they pass through a distinct 

 subadult phase in which the organs necessary for 

 copulation are developed and those required for 

 generation are dormant or developing. The sub- 

 adult stage lasts for two summer seasons and most 

 female blue sharks on the continental shelf in the 

 western North Atlantic are in this stage. 



Examination of sex organs in female blue 

 sharks of various sizes reveal that like the male 

 claspers, growth is quite regular in the ovary and 

 oviduct. The oviducal gland exhibits some differ- 

 ential growth after 100 cm body length is attained 



457 



