Ultrastructure of the Termite-Associated Fungus Laboulbeniopsis Termitarius

Abstract

SUMMARY Ultrastructural features of Laboulbeniopsis termitarius suggest that this termite-associated fungus may belong to ascomycetes. Spores are formed without cleavage vesicles typical of sporangial fungi, abundant epiplasm remains, and septal walls between cells of simple thallus bear a single pore. A single ascus forms from base of terminal sporogeneous cell, but deliquesces by time of spore maturation. Haustoria are not present, although secretory vesicles were noted in two areas of foot cell suggesting mode of attachment. Although many aspects of this fungus suggest relationships with Laboulbeniales, uniascal thallus, one-celled spores, and lack of haustoria exclude Laboulbeniopsis from this taxon. Thaxter (1914, 1920) described a number of fungi from insects which could not be clearly assigned to existing taxonomic groups. He pointed out their unclear taxonomic position and lack of knowledge of their nutritional relationships with insects on which they occur. Two of these monotypic genera, Laboulbeniopsis and Coreomycetopsis, were described and placed by Thaxter (1920) in the limbo genera incertae sedis, and in same paper he suggested with reservation that Laboulbeniopsis might be accommodated in Thaxteriolae with Thaxteriola Speg., Endosporella Thaxt., and possibly Entomocosma Speg. Laboulbeniopsis termitarius and Coreomycetopsis oedipus were not mentioned again for fifty years until Kimbrough and Gouger (1970) reported them from Florida on species of termite genus Reticulitermes. Their light microscopy study added little to what was known about mature thallus. However, many aspects of thallus development, spore formation, and spore liberation and attachment were discussed. Since many morphological details of L. termitarius cannot be discerned with certainty at light microscopic level, we undertook