Jensen et a\ The reproductive biology of Lamna nasiis in the western North Atlantic Ocean 



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as flaccid uteri with trophonemata and reduced ovaries 

 containing few maturing or mature oocytes. Juvenile 

 females have small undeveloped ovaries with white to 

 clear oocytes; the uterus appears narrow and constricted, 

 and the oviducal gland is seen as a barely perceptible 

 widening of the oviduct. The juvenile and mature virgin 

 sharks that we examined had a membrane separating the 

 vagina from the cloaca, whereas mature (reproductively 

 active) sharks had no membrane. In nongravid females, 

 maturity is based on the presence of mature oocytes in 

 a developed ovary, an expanded uterus, a well-developed 

 oviducal gland, internal and external mating scars, and 

 the absence of a vaginal membrane. The smallest mature 

 female in our sample was 210 cm FL based on the absence 

 of a vaginal membrane and the condition of the internal 

 reproductive organs, and the largest immature female was 

 230 cm FL based on the presence of a vaginal membrane 

 and internal organ condition. Fifty percent of the female 

 porbeagle population was mature at 218 cm FL (Fig. 4A). 



Mating injuries 



Fresh mating scars, containing at least small areas of 

 unhealed dermal lacerations, were observed from late 

 September through mid-December, during which time 

 most adult females appeared to have recently mated or 

 were in the early stages of pregnancy. Scars and cuts 

 were often observed on either or both pectoral fins as 

 single or multiple jaw outlines, and the trailing edge of 

 the fin was often shredded. Tooth scrape marks, puncture 

 wounds, and gouges, some as open, penetrating subdermal 

 lacerations, were observed mainly along the posterior lat- 

 eral, dorsal, or ventral body surface. None of the wounds 



appeared to have penetrated the abdominal wall nor were 

 they debilitating. No infected or necrotic tissue was seen 

 in these wounds. Most mature female porbeagles had dis- 

 tinct fresh or healed mating scars. 



Internal mating scars were observed on the vaginal walls 

 from late September through mid-December. The scars 

 were generally small, round to ovoid, hematose marks on 

 an otherwise white to light yellow vaginal wall. These were 

 probably caused by the spur that holds the clasper in place 

 during copulation. 



Gravid females, embryo growth, and nutrition 



Data from 80 litters and 309 embryos were obtained from 

 gravid females sampled from mid-September through 

 April. In addition to embryos, these females had several 

 different types of egg capsules in their oviducal gland, 

 isthmus, and uteri. These were empty capsules, capsules 

 containing one large ovum without a visible embryo (single 

 ovum capsules), capsules with one developing embryo and 

 attached yolk sac, capsules with 22-45 blastodisc-stage 

 ova, and capsules containing 8-100 nonblastodisc-stage 

 ova (nutritive capsules), some appearing atretic and in 

 which individual ova were difficult to detect. The number 

 of capsules present in each uterus ranged from none to 63 

 (Fig. 8). 



The proportion of mature nongravid females with recent 

 mating scars, but no obvious fertilized ova, decreased from 

 September through December, whereas the proportion of 

 gravid females increased (Fig. 9). All mature females ex- 

 amined in December were gravid. During October, several 

 mature females contained either parts of, or entire, sper- 

 matophores in the uteri, but no ova capsules, indicating 



