RESPIRATION OF OOCYTES, UNFERTILIZED EGGS AND FERTILIZED EGGS FROM PSAMMECHINUS AND ASTERIAS

¹ Wenner-Gren's Institute for Experimental Biology, University of Stockholm

In Cartesian diver experiments on the oxygen consumption of oocytes, unfertilized eggs and fertilized eggs from the sea-urchin Psammechinus miliaris and the starfish Asterias glacialis it was found:

1. The respiration of ripe Ps. eggs declines rapidly after they have been removed from the ovary into sea water. Starting at a rate that may exceed that of newly fertilized eggs it has thus, after some hours, attained a comparatively low and fairly constant level. The declining curve on kinetical analysis proves to be composed of a monomolecular and a constant part. The respiration curve of Ps. oocytes is of a similar type. In Ast. oocytes and eggs the respiratory decrease, though present, is not so prominent as in Ps. cells (3.112.1, 3.113, 3.122, Fig. 2).

2. Though there is a real difference in size between the eggs of the two Ps. phenotypes (the littoral Z-form and the S-form of the depths) no difference is found in the rate of respiration (3.112.2, 3.114).

3. Measurements on Ps. oocytes and eggs some hours after removal from the ovary show that the oocytes have only a slightly higher respiration than the eggs. The earlier investigations (Lindahl and Holter, 1941) on Paracentrotus lividus eggs showed that these oocytes maintain a rate of respiration even higher than that of the newly fertilized egg. The findings in Par. might be ascribed to a slow respiration decrease in the oocytes, whereas the decrease is more rapid in the eggs. In Ps. the decrease is about equal in oocytes and eggs (3.112.2, 3.113, 4, Fig. 6).

4. In Ast. the primary oocytes respire at a much lower rate than do the secondary ones or the eggs (3.122, 4, Fig. 6).

5. In Ps. there is a gradual slight decrease in egg respiration with advancing cytoplasmic maturity (3.113).

6. In both Ps. and Ast. the respiration of oocytes in ovarial fluid seems to be of the same order of magnitude as that of oocytes in sea water (3.113, 3.122).

7. The shape of the respiration curve in Ps. after fertilization is in full concordance with earlier results obtained with different techniques by Gray (1926) and Lindahl (1939) (3.21, Fig. 3).

8. The value of the rise in respiration, that occurs in sea-urchin eggs on fertilization, may entirely depend on where on the slope of the decreasing egg respiration curve fertilization occurs. (This rise is characteristic for sea-urchin eggs and has repeatedly been found by earlier investigators.) It is thought that on natural spawning the rise is rather feebly marked because of early fertilization, and that correspondingly the low level respiration of the unfertilized egg may not be reached (3.21 , 4, Figs. 3 and 7).

9. In Ast. there is no immediate rise in respiration after fertilization, but there is a gradual rise which exactly resembles the exponential increase in newly fertilized sea-urchin eggs (after the first sudden increase has passed). The rise from the oocyte respiration level to that of the egg will, under natural conditions, not occur outside the ovary, as the cells are shed with broken down nuclear membranes (3.22, 4, Figs. 4, 7 and 8).

Cleavage rates are given up to the sixth mitosis for Ps., Ast. and Echinocardium cordatum; hatching time is noted (3.3, Fig. 5).

It is discussed whether the decrease in respiration of the unfertilized sea-urchin egg after its removal from the ovary has any possible significance for the biochemical aspects of the sea-urchin egg respiration (4).

If the respiration rates found in this investigation are compared on a cell volume basis it is found that the Ast. egg will not fit into the generalized scheme of Whitaker (1933) for marine invertebrate eggs; it is discussed why the Ast. egg respiration is so comparatively low (4, Fig. 6).

This article has been cited by other articles:

				C. M. MONTGOMERY and J. W. BAMBERGER Action of Parapyruvate on Early Development of Strongylocentrotus Purpuratus Science, November 18, 1955; 122(3177): 967 - 968. [PDF]