132 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



ACCOUNT OF INDIVIDUAL EXPERIMENTS 

 Development at 45° F. 



The sea lamprey eggs could not make even a 

 good start toward development in a constant 

 temperature of 45° F. The first two cleavages 

 (stages 1 and 2) proceeded very slowly and all eggs 

 were dead before the third cleavage was completed 

 (tables 4 and 5; fig. 27). 



Table 4. — Living and dead lamprey embryos per sample 

 and their stage of development at 45° F. {7.2° C.) 



100 

 80 

 60 

 40 

 20 

 



100 



80 

 60 

 40 

 20 



iioo 

 ;eo 



I 60 

  40 



! 20 



J 

 ■100 



80 



60 



40 



20 



50°F 



52.5°F 



60°F 



15 20 25 30 35 40 



DAY OF SAMPLING 



Table 5. — Mortalities of sea lamprey eggs reared at a 

 constant temperature of 4S° F. {7.2° C.) 



1 More than 99.6; actually all embryos (238 specimens) were dead in the 

 sample taken at H6 hours. 



Stage 1 lasted about 20 hours; stage 2 com- 

 menced at the 19th hour and lasted beyond the 

 47th hour, when a highly defective stage 3 ap- 

 peared (tables 4 and 6; fig. 28). Many 3-celI 

 embryos were found along with a few abortive 

 4-cell embryos, in which the cleavage furrow 

 seemed to undergo regression. 



Throughout the samples, beginning with the 

 sixth at 1 1 hours, the eggs began to vacuolate and 

 to fragment yolk into the perivitelline space, in 

 short, to die and disintegrate. Beginning with 

 the 19th sample, at 47 hours nearly 90 percent 



100 

 80 

 60 

 40 



20 







100 



80 



60 



40 



20 



100 

 80 

 60 

 40 

 20 





 100 



80 



60 



40 



20 





 100 



80 



60 



40 



20 







65° F 



I I ' I I I ' I ' 



70° F 



75°F 



77.5°F 



80°F 



10 15 20 25 



DAY OF SAMPLING 



I I I ' I i I ' I I ' I ' 



30 



35 



40 



Figure 27. — Percentage of dead embryos in daily samples from sea lamprey eggs reared at 10 different constant temp- 

 erature levels. The day-by-day records end when the percentage of dead in the samples reached and remained at 

 100, or with the onset of hatching. A broken line connects the last recorded daily sample with the terminal sample 

 (T). At 77.5° and 80° live embryos occurred in the earlier samples of the first day but none in the later ones. 



