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

Abstract

In Cartesian diver expts. (new calculating formulas given) on the oxygen consumption of reproduction cells from P. miliaris (Ps.) and A. glacialis (Ast.) it was found: Upon removal from the ovary into sea water respiration of ripe Ps. eggs starts at a rate that may exceed that of the newly fertilized egg, declines rapidly and, after some hrs., attains a low and fairly constant level ([image] 0.5x10-4 microliters/egg and hr. at 18[degree]C). Kinetical analysis proves the declining curve to be composed of a monomolecular and a constant part. Ps. oocytes have a similar respiration curve. The same applies to Ast. oocytes and eggs, though the decrease is less prominent.[long dash]The eggs of 2 Ps. phenotypes (littoral and depth-forms) differ in size (diam.[image]95 and 104 micra, respectively) but not in respiration.[long dash]Some hrs. after removal from the ovary Ps. oocytes show only slightly higher respiration than the eggs. In Ast. the primary oocytes respire at a much lower rate ([image] 1.15x10-4 microliters/egg and hr.) than do the secondary ones or the eggs ([image]2.5xl0-4 microliters/egg and hr.; diam. [image]170 micra). 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. In Ps. there is a gradual slight decrease in egg respiration with advancing cytoplasmic maturity.[long dash]In Ps. respiration after fertilization is followed until after hatching; in Ast. over the first cleavage. The nature of the respiratory rise on fertilization in sea-urchins is discussed. (Respiratory rate in Ps. 2 hrs. after fertilization [image]1.8x10-4 microliters/embryo and hr.) In Ast. there is no immediate rise after fertilization; instead there is a gradual one, exactly resembling the exponential increase in newly fertilized sea-urchin eggs (after the first sudden increase has passed).[long dash]Cleavage rates are given up to the 6th mitosis forPs., Ast. and Echinocardium cordatum; hatching times are noted.[long dash]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 respiration.