GENE DEPENDENCY OF VEGETALIZATION IN SEA URCHIN EMBRYOS TREATED WITH LITHIUM

Abstract

Embryos of Paracentrotus lividus were raised in sea water; in sea water with 12 ug./ml. actinomycin D; in sea water with 0.033 M lithium and in sea water containing both lithium and actinomycin D. The embryos were transferred into the media at the 8-cell stage and exposed for 5.5 hr.; thereafter they were returned to normal sea water. Embryos were fixed at specific time intervals and living specimens were also observed. Results indicate that the lithium concentration and time of exposure used gave a weak but definite vegetalization in a high percentage of larvae. Eggs suspended in sea water containing lithium and actinomycin, or only actinomycin reveal that the antibiotic blocks the transfer of information for both the animal and vegetal anabolic pathways. The inference is that gene activation is a link in the vegetalization following exposure to lithium. Exposure to actinomycin alone causes a tendency to animalization. The development of the embryo becomes more balanced after exposure to the combined action of lithium and actinomycin; however a certain inhibition prevails which is manifested in subnormal outgrowth of skeleton rods and arms.