PERKINS: DEVELOPMENTAL RATES OF NORTHERN LOBSTER EMBRYOS 



onset of eye pigment to hatching at a given tem- 

 perature; and A'2 is the unknown time required 

 from extrusion to hatching at the same temper- 

 ature as Xi. Templeman (1940, p. 74) used a 

 similar method to find unknown developmental 

 rates. The requisite times for development of 

 lobster embryos at certain temperatures are 

 summarized in Table 2. The relationship be- 

 tween water temperature and the average in- 

 crease in eye index of lobster embryos, in mi- 

 crons per week, is linear at temperatures be- 

 tween 5° and 25° C. The index of the embryonic 

 eye must increase to approximately 560^t at 

 hatching. If eggs are encountered with eyed 

 embryos, their eye index may be subtracted 

 from 560 and the difference divided by the value 

 calculated from the following equation: 



Y = —8.3151 + 2.6019 (X) 



where Y is the increase of the eye index in mi- 

 crons per week, and X is the developmental tem- 

 perature. The resulting quotient is the average 

 number of remaining weeks required for the em- 

 bryos to hatch, depending on genetic variation 

 and the differential rate of development noted 

 earlier. 



SUMMARY 



1. Once eye pigment has been formed, the 

 course and rate of development of lobster em- 

 bryos may be monitored by the periodic mea- 

 suring of the eye of the embryos. 



2. Lobster embryos develop differentially, 

 under the same thermal conditions, depending 

 on their age or extent of development when they 

 are subjected to a given thermal environment. 



3. As water temperature has a direct effect 

 on the developmental rate of lobster embryos, 

 that rate may be manipulated by adjusting the 

 water temperature of holding tanks to insure 

 periodic hatches of larvae throughout the year. 



LITERATURE CITED 



Herrick, F. H. 



1890. The development of the American lobster, 

 Homarus americarms. Johns Hopkins Univ. Circ. 

 9: 67-68. 



1896. The American lobster : A study of its habits 

 and development. Bull. U.S. Fish Comm. 15: 

 1-252. 

 Squires, H. J. 



1970. Lobster (Homarus americanus) fishery and 

 ecology in Port au Port Bay, Newfoundland, 1960- 

 65. Proc. Natl. Shellfish. Assoc. 60: 22-39. 

 Templeman, W. 



1940. Embryonic developmental rates and egg-lay- 

 ing of Canadian lobsters. J. Fish. Res. Board 

 Can. 5: 71-83. 



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