Abstract
This study utilized ultramicrotomy, coupled with transmission electron microscopy (TEM) to investigate the ultrastructure of Coreomyces, a member of an unusual group of arthropod associated fungi, Laboulbeniales (Ascomycota). Ultra-thin sections of the fungal cell wall reveal a tri-layered structure, bounded by a double membrane, and lacking perforations. This implies that all nutrition required for development of the fungal thallus is obtained directly from the host via the attachment cell. Ultrastructural details presented for any member of Laboulbeniales include (1) detail of a receptacular septum, revealing the presence of septal pores, (2) sections through the ascospore attachment pad, illustrating a mesh-like fiber network, and (3) the occurrence of a series of invaginations, interpreted as flask-like pores, situated along the outer wall of mature ascospores. Details of the development of the perithecium, asci and ascospores, are also presented, based on serial sectioning through the terminal cell of the thallus.