FISHERY BULLETIN: VOL. 70, NO. 1 



the five females held in water of seasonal tem- 

 perature, the youngest eggs were at lower tem- 

 peratures than the older at the same age, making 

 assessment of differential developmental rate 

 difficult. However, of the seven egg masses held 

 at 22.6° C the embryos of least development at 

 the start developed faster at comparable levels 

 of development than the more advanced embryos. 

 The differential rate of development of lobster 

 embryos, at the same temperature, seems to im- 

 ply that in a given population where extrusion 

 of eggs may be somewhat staggered in time 

 among the females, hatching of the eggs would 

 occur during a more limited period, providing 

 the egg-bearing females occupied the same ther- 

 mal environment. 



SOr 



70- 



X 



u 



t- 



X 





60 



50 



40 



» 30 



20 - 



10 



• = OBSERVED VALUES 

 O « CALCULATED VALUES 



(•) 



10 12 14 16 le 20 22 

 TEMPERATURE OF WATER (°C ) 



24 26 



Figure 3. — The number of weeks for lobster eggs to 

 complete the embryonic period at various temperatures. 

 Line A represents the time required from onset of eye 

 pigment in the embryos; line B represents the time re- 

 quired from extrusion to hatching. Points in paren- 

 theses indicate times required at the mean temperature 

 of a fluctuating thermal environment. 



RATES OF DEVELOPMENT AT 

 VARIOUS TEMPERATURES 



The times required for the embryos to hatch 

 at various temperatures are shown in Figure 3. 

 Line A represents the time required for the em- 

 bryos to hatch after the formation of eye pig- 

 ment; line B represents the time required from 

 extrusion to hatching. Most of the points in each 

 line indicate the time required to complete de- 

 velopment at constant temperatures. A few 

 (points in parentheses), representing the time 

 required for total development at the mean tem- 

 perature of a fluctuating thermal environment, 

 have been included as well. For example, the 

 average time required for total development of 

 the eggs of the five females held under seasonal 

 conditions was 49.7 weeks. The mean water 

 temperature during the period was 8.1° C. These 

 values are virtually the same as would be expect- 

 ed if the water was held constantly at 8° C. 



All values showing time from onset of eye pig- 

 ment to hatching were observed. The times re- 

 quired from extrusion to hatching at five tem- 

 peratures were also observed. To find the 

 unknown time required from extrusion to hatch- 

 ing, at other temperatures, I used the following 

 equation: 



At = Az 

 Xi X2 



where Ai was the observed time from onset of 

 eye pigment to hatching at 20° C; A2 was the 

 observed time from extrusion to hatching at 

 20° C; Xi was the observed time required from 



Table 2. — Number of weeks required from extrusion to 

 onset of eye pigment, onset of eye pigment to hatching, 

 and to hatching at certain temperatures, at salinities 

 near 31%c. 



Weeks required from 



Water temperature 



C C) Extrusion to onset 



of eye pigment 



Onset of eye 



pigment to 



hatching 



Extrusion to 

 hatching 



5 

 10 

 15 

 20 



25 



40 

 9 



S 



A 

 3 



120 



30 



18 



12 



9 



160 

 39 

 23 

 16 



12 



98 



