Studies on controlled and released respiration in animalized and vegetalized embryos of the sea urchin Paracentrotus lividus

Abstract

Previous studies [6, 16] on controlled and released respiration have been continued on animalized or vegetalized whole embryos of the sea urchin Paracentrotus lividus. The animalization of the embryo was brought about by exposure to trypsin (0.05 per cent). In the advanced cleavage stage exposure to trypsin alone brings about a release which does not increase by addition of 2,4-dinitrophenol (DNP). In a blastula or mesenchyme blastula stage, however, the oxygen consumption in embryos exposed to trypsin is equal to that of the control in sea water. The addition of DNP to trypsin treated embryos caused a release of respiration which is significantly higher than the release occurring in embryos in pure sea water (Figs. 1 and 3). The vegetalization was brought about by addition of lithium (0.074 M) to the sea water. This concentration depresses the oxygen consumption in the stages examined. Upon addition of DNP, it gives a “normal” release of respiration in the advanced cleavage stage, whereas, in the blastula and mesenchyme blastula stage, there is no release. The behaviour of animalized and vegetalized embryos with respect to release of respiration is in parallel with that of separated animal and vegetal halves [6]. The different values of released respiration may be due to the number of respiratory chains available in the cells. At the concentration used lithium seems to cause a regression of functional respiratory enzymes, a process, which is apparent from the blastula stage on. The role of mitochondria in the phenomena studied is briefly considered.