FISHERY BULLETIN: VOL. 77. NO. 2 



total length, defined by Bigelow and Schroeder 

 ( 1948) as a caliper measurement along the body 

 axis from the snout to a perpendicular extended 

 from the upper caudal. I have converted all refer- 

 ences to blue shark total lengths in the literature 

 to fork lengths in centimeters using a regression^ 

 derived from a sample of 554 males and females 

 between 93 and 282 cm FL (r = 0.995). 



Clasper length (posterior free tip to the free 

 trailing edge of the pelvic fin lateral to each 

 clasper) and internal organs were measured with 

 calipers to the nearest millimeter. 



Sharks were dissected as soon as possible after 

 being caught. Several adults were frozen whole 

 and dissected in detail at the laboratory. Speci- 

 mens for analysis and anatomical description 

 ranged in size from 1.1 to 264 cm and included 210 

 females and 114 males. 



A single ventral incision from cloaca to pectoral 

 girdle permits access to the body cavity. The size 

 and condition of internal organs of both sexes were 

 noted. To determine maturity and insemination, 

 both oviducal glands were excised carefully, with- 

 out squeezing, with several centimeters of adja- 

 cent oviduct. Oviducal glands and other histolog- 

 ical samples were preserved in Bouin's fixative 

 because it is compatible with the primary stain 

 (Mallory's Triple Stain). Larger organs were pre- 

 served in 107f Formalin.'' Tissues were prepared 

 by the paraffin method and sectioned to 10-15 /j.m. 

 In the latter part of the study a smear technique 

 was developed to quickly determine insemination. 

 This new technique, which obviates the need for 

 histological sectioning, is discussed in a later sec- 

 tion. 



RESULTS AND DISCUSSION 



Male Anatomy 



Testes and Epigiinal Organ 



The male blue shark has two equally developed 

 testes each embedded in the anterior portion of a 

 long irregular epigonal organ which has no known 

 reproductive function other than to support the 

 testes (Figures 1,2). Dissected from the epigonal 

 organ, the testis is cylindrical with rounded ends. 

 It is packed with tiny spheres averaging 0.3 mm in 



HEAD OF EPIDIDYMIS 

 DUCTUS EFFERENS 



TESTES 



MESORCHIUM 

 EPIDIDYMIS 



EPIGOhlAL ORGAN 



DUCTUS DEFERENS 



AMPULLA DUCTUS DEFERENS 



URE TER 



DUCTUS DEFERENS SPHINCTER 



UROGENITAL SINUS 

 UROGENITAL PAPILLA 

 COELOMIC PAPILLAE 

 (ABDOMINAL PORES) 



Figure l. — Male reproductive system in the adult blue shark, 

 general ventral view. 



DUCTUS £FFER£fJS 



TESTIS 



EPIGONAL OPCa^ 



LfrO/GS GiaND 



^Computed regression: FL = 1.73872 + 0.82995 TL. 

 'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service. NOAA 



Figure 2. — Testes, epididymis, and epigonal organ of the adult 

 male blue shark 



446 



