MALE PRONUCLEAR DEVELOPMENT IN STARFISH OOCYTES TREATED WITH l-METHYLADENINE

¹ Department of Anatomy, University of Iowa, Iowa City, IA 52242, The Marine Biological Laboratory, Woods Hole, MA 02543
² Department of Population Dynamics, John Hopkins School of Hygiene, Baltimore, MD 21205, The Marine Biological Laboratory, Woods Hole, MA 02543

Univ. of Iowa

Light and electron microscopic observations were carried out in order to examine the relation between male pronuclear development and the state of "cytoplasmic maturation" acquired by starfish oocytes under the influence of l-methyladenine (1-MA). Alterations were not apparent in the germinal vesicles or incorporated sperm nuclei of inseminated immature Asterias eggs for up to 5 hours in the absence of 1-MA. With the addition of 1-MA dramatic changes occurred in the germinal vesicle and ooplasmic region associated with incorporated sperm nuclei. These were followed by alterations in the sperm nucleus leading to the development of a male pronucleus. Pronuclear development in Asterias eggs inseminated at the germinal vesicle stage and then treated with 1-MA differed from that described for other organisms. Aside from the dilation of its perinuclear cisterna, the sperm nuclear envelope persisted intact throughout development. Dispersion of condensed chromatin occurred simultaneously throughout the whole of the sperm nucleus. These results suggest that factors necessary for pronuclear development do not exist in the ooplasm of immature starfish oocytes but arise following dispersal of germinal vesicle contents into the cytoplasm.