PARSONS: REPRODUCTIVE BIOLOGY OF ATLANTIC SHARPNOSE SHARK 



were taken, using those indicators of maturity 

 reported by Clark and von Schmidt (1965). Dis- 

 sections of males allowed examinations of the re- 

 productive systems and measurements of testicu- 

 lar length, weight, and volume. 



Testes and epididymides were removed from 

 some specimens, preserved in 10% Formalin 2 , 

 and returned to the laboratory. Histological sec- 

 tions of testes as well as epididymides were pre- 

 pared. The tissues were embedded in paraffin, 

 sectioned at 7 jum, stained with hematoxylin and 

 eosin, and examined with phase contrast micros- 

 copy. Sperm smears were also examined under 

 the microscope. 



After obtaining weight and total, fork, and 

 standard lengths, female specimens were dis- 

 sected and their reproductive organs examined. 

 Ovarian lengths as well as the number of ovarian 

 eggs and their diameters were recorded. When 

 embryos were present, the number, sex, total 

 length, and wet weight were determined for each 

 uterus. 



When appropriate, the data were keypunched 

 and statistically evaluated, using the McGill 

 University System for Interactive Computing 

 (MUSIC) time sharing system. The STATPAK 

 computer program, a statistical package con- 

 taining 23 statistical analyses and data modifica- 

 tion routines, was used to analyze the data. 



RESULTS AND DISCUSSION 



Reproductive Anatomy 



Ovarian Structure 



Forty-two Atlantic sharpnose shark ovaries 

 were examined during the study period. E lasmo- 

 branchs possess a great deal of variability in the 

 structure of the ovary (Dodd 1972). The ovary of 

 the adult Atlantic sharpnose shark is an un- 

 paired, tear-shaped organ, 6 to 10 cm long and 

 3 to 5 cm wide. Unlike other carcharhinids, the 

 ovary of the sharpnose shark is developed on the 

 left side only. Structure and location of the sharp- 

 nose shark ovary (aside from its position on the 

 left side of the body cavity) are similar to that 

 found in the blue shark (Pratt 1979). The adult 

 sharpnose shark's ovary, during most of the year, 

 is filled with many small (ca. 2.0 to 5.0 mm) 

 oocytes embedded in dense connective tissue. 



Outside the breeding season the ovary of the 

 adult female contains an average of about 30 

 oocytes greater than ca. 2 mm in diameter. These 

 oocytes serve as a "pool" from which the next gen- 

 eration of eggs will be drawn. In some ovaries, 

 unusual, bright red, fluid-filled structures were 

 found, ranging from about 2 to 8 mm in diame- 

 ter (Fig. 2). These structures are assumed to be 

 oocytes in a state of atresia that had failed to ovu- 

 late during the most recent breeding period. 

 These preovulatory structures may be "corpora 

 atretica," which are derived from egg-containing 

 follicles. In Cetorhinus maximus the corpora 

 atretica are believed to arise from follicles that 

 have attained a diameter of about 1.0 mm (Dodd 

 1972). The corpora atretica consist of vacuolated 

 peripheral cells and a central cavity and are well 

 vascularized (Dodd 1972). 



ANTERIOR 



Normal 

 Developing Ovum 



Atretic Ovum 



2 Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



POSTERIOR 



FIGURE 2.— Diagram of an Atlantic sharpnose shark ovary 

 taken in December from a 93 cm gravid female. A red, fluid 

 filled (atretic?) ovum can be seen in the center of the ovary. 



Ovulation 



As ovulation approaches, rapid yolk deposi- 

 tion occurs in four to eight of the many smaller 

 oocytes. The "selected" oocytes are preferentially 

 yolked, while the others undergo atresia. At or 

 near ovulation the ovary appears highly vascu- 

 larized and the large, yellow oocytes fill the en- 

 tire ovary (Fig. 3). Measurements of both ovarian 

 and uterine oocytes suggest that ovulation occurs 

 at an egg diameter of about 20 mm. 



After ovulation, the eggs move through the 

 body cavity into the ostium tubae which forms 

 the anterior end of the oviduct. In most cases 



63 



