SEM Studies on Operculum Structure in the Myxomycete Trichia Crateriformis

Abstract

Scanning electron microscope studies have been conducted on the operculum of sporangia of Trichia crateriformis and its structure has been compared with that of other operculate Myxomycetes. The operculum of T. crateriformis consists of a single layer of sporelike bodies that have cell walls ornamented with warty excresences similar to those of the spores. It adjoins the membranous peridium of the sporangium in a transition region which constitutes the dehiscence zone. In other taxa with operculate sporophores examined the operculum is membranous and has a structure generally similar to that of its associated peridium. The type of operculum in T. crateriformis may be unique for the Myxomycetes. Several species of Myxomycetes form sporangia furnished with a well-defined operculum. Species exhibiting this characteristic are Metatrichia vesparium (Batsch) Nann-Brem., certain species of Craterium and Licea, Perichaena depressa Libert, and Trichia crateriformis Martin. During the course of some scanning electron microscope (SEM) studies of types of authenticated specimens of taxa in the Trichiaceae, we observed that the operculum of the sporangium of T. crateriformis is strikingly different in structure from that of its contiguous peridial wall. The T. crateriformis operculum was noted to consist of discrete spore-like units with ornamented wall surfaces similar to those of the spores. A report on this apparently unique type of operculum structure is presented in this communication.