CHAPTER 7 



METABOLIC AND OTHER CHANGES AT 

 FERTILIZATION 



This chapter consists of a list, with occasional notes, of the principal 

 changes (or lack of changes) which have been reported to occur at, 

 or soon after, fertilization. Morphological, structural and certain 

 other changes are dealt with in separate chapters. The references 

 are not intended to be all-inclusive and little attention has been 

 paid to priority of discovery. References with an asterisk after 

 them are brief notes, f. stands for fertilized or fertilization; u. for 

 unfertilized. 



(i) Increase in permeability to sparingly ionized solutes, e.g., 

 water, /j = o-i (u.), 0-2-0-4 (f.). A. punctulata {R. S. Lillie, 1916; 

 Lucke et al., 193 1). 



The permeability constant k is the amount of water ((j.^), entering 

 the cell in unit time (i min.), through unit area {[x^), under unit differ- 

 ence of osmotic pressure (i atm.). The change in k occurs 2-4 min. 

 after fertilization and is complete in 10 min. (Lucke & McCutcheon, 



^932). 



Measurements of permeability changes after fertilization or par- 

 thenogenetic activation of sea-urchin eggs have recently been made by 

 Ishikawa (1954), Fig. 14. When the eggs of Hemicentrotus pulcherri- 

 mus are activated by treatment for 12 min. with sea water contain- 

 ing butyric acid (50 ml. sea water + 3 ml. N/io butyric acid), there is, 

 according to this worker, no breakdown of cortical granules, no mem- 

 brane formation and no increase in permeability to water. This casts 

 some doubt on the importance of granule breakdown (see pp. 9-10), 

 which Ishikawa thinks is responsible for the increase in permeability, 

 in activation. Similarly, Kusa (1953) was able to activate salmon eggs, 

 parthenogenetically, without the cortical alveoli breaking dov/n. 

 Sugiyama (1953) says that butyric acid treatment does cause granule 

 breakdown and membrane formation in the eggs of Hemicentrotus 

 pulcherrimiis. The shape of the normal fertilization curve in Fig. 14 is 

 similar to that obtained by Hobson (19320), using the eggs of Psam- 

 mechinus miliaris. 



(I'l) Osmotically inactive fraction, or 'non-swcllable volume', 

 7-3% in u. and 27-4% i^i f. eggs. A. punctulata (Shapiro, 1948). 



In this paper, Shapiro states that there is a 2-7% increase in the 

 volume of this egg at fertilization, see p. 20. 



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