Comparative Sem Observations of Sporophore Characteristics in Three Species of Didymium (Myxomycetes, Physarales)

Publisher Website
Google Scholar
Abstract
Sporophores of twelve isolates of D. iridis and 9 collections of D. nigripes and D. ovoideum were examined by scanning electron microscopy (SEM). Detailed attention was given to 3 sporophore characteristics: spore ornamentation, capillitial and lime crystal morphology. Intraspecific morphological distinctions in these characteristics were not found among heterothallic and nonheterothallic isolates of D. iridis. However, interspecies comparisons showed that D. iridis was the most variable species for spore processes and lime morphology. In Ky 1 of D. iridis, connate verrucae frequently produced a crude noncontinuous reticulum on the spore wall. This tendency was not prominent in D. nigripes, D. ovoideum or other D. iridis isolates. Furthermore, Wa 1 (D. iridis) possessed both stellate and encrusted botryoidial lime on the same peridium. These exceptional characteristics were either not observed or rarely suggested in D. nigripes and D. ovoideum. Even though several collections of D. nigripes had homogeneously verrucate spores, in most collections they were similar to those produced by D. iridis and D. ovoideum. Each species displayed a capillitium which was tubular or sheet-like and either roughened or verrucate. Consequently, capillitial morphology could not be used to distinguish among the species. Curiously, several collections of D. ovoideum possessed a verrucate capillitium as well as a verrucate inner peridium. The significance of a verrucate inner peridium in D. ovoideum was not assessed. Peridial lime in D. iridis, D. nigripes and D. ovoideum was too similar to be useful in distinguishing these closely related species from one another.