PERKINS: DEVELOPMENTAL RATES OF NORTHERN LOBSTER EMBRYOS 



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50 100 150 200 250 300 350 400 450 500 

 EYE INDEX AT START (MICRONS) 



Figure 2. — Line A represents the different rates of in- 

 crease of the eye index, in microns per week, of the em- 

 bryos of the five lobsters held in the same tank, under 

 seasonal conditions, from November 7, until hatching. 

 Line B represents the different rates of eye increase 

 of the embryos of seven females held at a constant tem- 

 perature of 22.6° C. Size of eye index at the starting 

 time is plotted against the corresponding rate of increase 

 of the eye index up to the time of hatching. 



Table 1. — Lobster number, carapace length of female, 

 age of eggs 10 January, increase of eye index of embryos 

 from 10 January to 26 March, and the total develop- 

 mental time for the embryos of the five female lobsters 

 held under seasonal water conditions at the Boothbay 

 Harbor Laboratory. 



Lobster Carapace 



number 'f"9\'i 

 (mm) 



Area of 

 capture 



Age of eggs 



Increase of Total 



10 January , eye index weeks 



(weeks) 7J";''°"'/.T/^' u /?• 



' 10 Jan. -26 Mar. hotchmg 



surable increase in development during this time, 

 whereas some development was noted in the em- 

 bryos of the other egg masses. In fact, the em- 

 bryos in the oldest egg mass showed no measur- 

 able increase from the second week of December 

 to the middle of the following April. The num- 

 ber of weeks during the winter in which no de- 

 velopment could be measured, for each egg mass, 

 was as follows (as in Table 1, lobsters are num- 

 bered according to the age of their egg mass) : 



weeks 



ure 2(A) the rate of eye increase (microns per 

 week) of the embryos in each egg mass for the 

 remainder of the developmental period is plotted 

 against the corresponding eye index taken on 

 November 7. The same result is obtained if 

 the age of an egg mass is substituted for its eye 

 index on the abscissa. Rates of increase were 

 calculated by dividing the total increase of the 

 eye index by the total number of weeks the em- 

 bryos took to complete development after No- 

 vember 7. The increase in eye index (microns 

 per week) of embryos in each egg mass, for the 

 period January 10 to March 26, is presented in 

 Table 1, During this time the water temper- 

 ature ranged between 0.1° and 1.5° C; the mean 

 was 1.0°. This was the coldest 10-week interval 

 of the developmental period. The embryos in the 

 oldest egg mass exhibited no noticeable or mea- 



The rates of increase (microns per week) in 

 eye index for the embryos of seven lobsters 

 held at a constant temperature of 22.6° C are 

 indicated in Figure 2(B). These females came 

 from offshore canyons of the continental shelf, 

 off New England, The ages of these egg masses 

 were not known, but the eye index of the embryos 

 in each was measured before the females were 

 placed in the warm water. The increase in eye 

 index of the embryos in each egg mass was mon- 

 itored weekly until hatching. Times and rates 

 pertain only to the time spent at 22.6° C. Al- 

 though one might expect that in a given time in- 

 terval, at the same temperatures, younger em- 

 bryos would develop faster than older ones, it 

 might also be expected that the younger embryos 

 would assume the slower growth rate of the older 

 when they eventually reached the same age. Of 



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