THE RESPIRATION OF SPISULA EGGS

Abstract

O2 consumption of unfertilized eggs of Spisula solidissima decreases gradually after removal from the ovary; mean rate immediately after shedding 3.8 x 10-5 [mu]l O2 x egg-1 x hour-1; 8 hours later 3.0 x 10-5. Post-fertilization rate is independent of the rate before fertilization; 30 minutes after fertilization it has a value of 3.0 x 10-5. The rate increases gradually during development. Measurements of CO2 output indicate a respiratory quotient of 0.7 before fertilisation (fat utilization); after fertilization there is a gradual increase toward unity (carbohydrate predominance). Early development up to the swimming blastula stage is described. The Cartesian diver technique was used for the gas exchange measurements. General conclusions for marine eggs from a comparison of the clam and echinoderm egg respirations: (1) Pre-fertilization respiration is dependent on internal substrate conditions; it varies in magnitude according to time elapsed from shedding. (2) After fertilization more uniform rates prevail, connected with the morphogenetic work to be done. (3) Pre- and post-fertilization respirations are independent processes; probably different sources of substrate are utilized. (4) Fat reserves are oxidized immediately after fertilization; later on carbohydrate is the main source.