Another species complex in myxomycetes: diversity of peridial structures in Lycogala epidendrum

Lycogala epidendrum is a conspicuous and widespread myxomycete that has not undergone taxonomic revision for more than a century. A detailed study of the peridium of fruiting bodies collected in Europe, Asia, North and Central America, and Australia has revealed at least 21 morphotypes and 39 ribogroups that are included within the general name L. epidendrum. One or more ribogroups can correspond to one morphotype, but all representatives of a certain ribogroup belong to the same morphotype. Peridial vesicles of L. epidendrum display single crystals, druses, oil droplets, granular accumulations, and orange pigment deposits. These vesicles show three different types of mutual arrangement. These features make it possible to distinguish among morphotypes and are promising diagnostic characters for species likely to be described as new for science. A factor analysis of morphological traits reveals that morphotypes of L. epidendrum differ from each other no less than is the case for other described species of the genus Lycogala. Plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy shows that the crystals in the peridial vesicles are built by compounds containing calcium. Calcium deposits are rare in bright-spored myxomycetes and have never been previously observed in the order Reticulariales. Vesicles of some morphotypes demonstrate the ability for fragmentation, which is reminiscent of cell division. This may indicate that they are formed by the release of portions of the plasmodial cytoplasm out side the developing fruiting body. All species of the genus, including L. flavofuscum, have peridial vesicles.

Automated summary

Lycogala epidendrum is a widespread myxomycete that has different morphotypes and ribogroups. The peridial vesicles show various features, such as crystals and calcium deposits, which are promising diagnostic characters. The presence of calcium deposits is rare in bright-spored myxomycetes and has not been previously observed in the order Reticulariales. The ability of vesicles to fragment suggests a possible mechanism of formation.