54 



Fishery Bulletin 98(1) 



O) 3 - 



11) 

 § 2 



1 - 



Variation 

 embryos. 



embryo with fangs was 38.3 cm, and the 

 smallest embryo without fangs was 33.9 

 cm. In the range of overlap, there were 12 

 embryos with fangs and 8 without fangs. 

 Therefore, the fangs are shed between 34 

 and 38 cm. 



Most of the larger embryos without 

 fangs possessed several series of develop- 

 ing, nonerect, nonfunctional teeth shaped 

 like those found in postnatal porbeagles, 

 except that they lacked lateral cusps. One 

 near-term litter had three embryos with 

 nonfunctional upper teeth but partially 

 erect lower teeth, whereas the fourth had 

 nonfunctional teeth in both jaws. 



The stomach contents consisted wholly 

 or mostly of viscous, amorphous, light yel- 

 low yolk. In many embryos there were 

 also discrete masses of clear, white or 

 greyish gelatinous material, probably the 

 remains of empty egg capsules, embed- 

 ded in the yolk. This gelatinous material 

 usually represented less than 10% of the 

 stomach contents and has been included 

 in the yolk weights reported below. Occa- 

 sionally we found shed fangs in the stom- 

 achs, but the thick glutinous nature of the yolk made 

 them difficult to find, and it was impossible to assess 

 their frequency or abundance. 



Embryonic total weight increased rapidly between 

 20 and 35 cm, changed little between 35 and 50 cm, 

 then increased again during the rest of the gestation 

 period (Fig. 10). Embryonic weight minus yolk weight 

 increased steadily throughout gestation. The weights 

 of five fi-ee-living juveniles shorter than 70 cm were 

 similar to the yoLk-fi-ee weights of the largest embryos. 



The weight of yolk in the stomach increased steadily 

 between 20 and 30 cm, before increasing rapidly to 

 peak at 30^2 cm (Fig. 11). Yolk weight at 30-42 

 cm varied from 0.39 kg to 1.82 kg, representing 

 26.7-80.8% of total body weight. Absolute and per- 

 centage yolk weight both generally declined at lengths 

 greater than 42 cm. Three embryos longer than 60 cm 

 still had around 1 kg of yolk in their stomachs, but 

 it represented a low proportion of their total weight 

 (ca. 17-22%^). All embryos longer than 50 cm had yolk 

 or gelatinous material in their stomachs, suggesting 

 that the yolk may not be completely digested before 

 birth. 



The spiral valve of the intestine contained a thick, 

 gritty, greenish-brown sludge that is the waste prod- 



A Embryo total weigtit 



• Embryo weigtit minus yolk 



O Juvenile total weigtit 





^ A A^ 

 AA A ^ 



«i^ 



A 

 A A 



If* 



A 



.V 





10 



20 



30 



40 



Fork length (cm) 



50 



60 



70 



Figure 10 



in total weight and yolkfree weight with length for porbeagle 

 Also shown are total weights of five small juveniles. 



* Not shown in the percent yolk weight panel of Fig. 11 because 

 embr>'o total weight.s were not mea.sured accurately. 



uct of yolk digestion. The smallest embryos dissected 

 ( 19.8-20.7 cm) contained small amounts of waste, and 

 the quantity of waste increased steadily throughout 

 gestation (Fig. 11). Intestinal contents composed the 

 greatest percentage of yolk-fi-ee weight at 30-50 cm. 

 Newborn porbeagles had smaller quantities of intes- 

 tinal waste than large embryos, suggesting that the 

 waste is retained until after birth. 



Liver weight increased exponentially with FL, show- 

 ing the most rapid increase above 55 cm (Fig. 11). 

 Relative liver weight also increased to a maximum in 

 the longest embryos. Postnatal porbeagles usually had 

 smaller livers, both in absolute and relative terms, 

 than those of the largest embryos, indicating that en- 

 ergy reserves stored in the liver are consumed by 

 the young after birth. 



The runts in two litters had low stomach and intes- 

 tine contents, and liver weights (Table 2). The 22.5-cm 

 runt in litter 1 had numerous short (1-3 mm) lacera- 

 tions on its distended abdomen, and a few elsewhere 

 on its body, presumably inflicted by the teeth of its 

 larger sibling. However none of the gashes had pen- 

 etrated the body cavity, and they did not appear to be 

 life-threatening. 



Five pairs of uteri containing embryos were ob- 

 tained. The orientation of the embryos could be deter- 

 mined for only five of the 10 uteri; these five uteri con- 

 tained embryos 38.2-62.6 cm long. In all cases, the 

 two embryos were facing in opposite directions. 



