214 



Fishery Bulletin 92(2). 1994 



a> 



c 



o 

 a. 

 ■o 



E 



o 



0) 



E 



i- 



flat; the medial portion of 

 the tail bud is thicker (Figs. 

 7C and 8B). The body of the 

 embryo appears flattened. 

 Although not distinguish- 

 able in preserved specimens, 

 Kupffer's vesicle is visible in 

 the live egg. 



Middle middle stage 

 (stage 14) Embryos have 

 14-16 myomeres. Differen- 

 tiation begins in eyes and 

 mid- and hindbrain. Fore- 

 brain very small and under- 

 developed. The tail bud mar- 

 gin is defined but still flat- 

 tened (Fig. 8C). The entire 

 length of the body is thicker. 

 Small melanophores are 

 scattered along the dorsum 

 between the hindbrain and 

 4/5 of body length (Fig. 7D). 



Late middle stage (stage 

 15) About 20-25 myomeres 

 are visible. Eye lenses are 

 formed. The liver appears as 

 a slight bulge in the body 

 wall, and the gut area is de- 

 lineated. The tail bud is thick and appears lifted 

 from the yolk surface with the margin attached (Fig. 

 7E). Pigment is darker than in the previous stage 

 and dendritic, extending from midbrain to tip of tail 

 bud and confined mostly to the dorsum. Nares, mid- 

 and hindbrain, and pectoral bud anlagen are visible 

 dorsally (Fig. 8D). 



450 

 400 

 350 

 300 

 250 

 200 

 150 

 100 

 50 

 



n — i — i — i — i — i — i — i — i — i — i r 



n — i — i — i — i — i — i — r 



I I I I I I I I L 



J I L 



1 2 3 



S 7 8 10 11 12 13 14 18 Ifl 17 18 10 20 BOM 



Developmental stage 



Figure 4 



Time (h) to midpoint of stage of Theragra chalcogramma eggs incubated at 3.8°, 

 5.7°, and 7.7°C. Fitted lines are results of regression model; symbols are observed 

 values. 



Early late stage (stage 16) Heart tissue begins 

 to expand when the embryo has about 24-36 myo- 

 meres. Forebrain differentiates from midbrain. The 

 tail bud lifts from the yolk surface (Figs. 7F and 8E) 

 and pigment forms two parallel rows dorsoposteriorly. 



Tail 5/8 around yolk (stage 17) The embryo 

 has 27-36 myomeres. More of the tail lifts from the 



Table 4 



Comparison of time (h) to estimated midpoint of five developmental milestones of Theragra chalcogramma 

 embryos incubated at 5-7°C. 



A C Matarese. Alaska Fisheries Science Center, National Marine Fisheries Service, 7600 Sand Point Way N.E., Seattle, WA 98115. 

 2 A .1 Paul, University of Alaska Fairbanks. Institue of Marine Science, Seward Marine Center Lab, P.O. Box 730, Seward, AK 99664. 



Values except for hatch estimated from Table 3 in Haynes and Ignell (1983). 50% hatch from Table 7. 

 1 Values except fur hatch estimated from Fig. 3 in Hamai et al. (1971). 

 ' Values except for hatch estimated from Fig 5 in Nakatani and Maeda (1984). 



