The ultrastructure of the thecal cell of the teleost, Oryzias latipes, during ovulation in vitro.

Ultrastructural examination of the follicular envelope of the teleost, Oryzias latipes, during ovulation in vitro showed that the follicle cell layer became increasingly dissociated. Microfilaments, measuring 50-70 A, were sparse in the thecal cells at the start of incubation, but were organized into bands after 5 hr, and into bundles after 10 hr of incubation. It is suggested that these microfilaments are contractile and are involved in cell movement during ovulation.