Tychosporium acutostipes, a new protostelid which modifies the concept of the Protosteliidae

Abstract

A new species of protostelid, Tychosporium acutostipes, was isolated from aerial dead plant parts from Fayetteville, Arkansas, and cultured using standard techniques for protostelids. This species grows and feeds well on bacteria but will not use yeasts as a food source. The trophic cell is typically a uninucleate amoeba which is morphologically very similar to that of Protostelium mycophaga except that it lacks the orange lipid droplets characteristic of that species. The development of the prespore cell and sporogen is identical to that found in P. mycophaga and its close relatives. The mature sporocarp has a much more rigid and straight stalk than P. mycophaga. The stalk typically tapers sharply to a point at its apical end. The single uninucleate spore is nearly spherical to slightly turbinate and is characterized by having a crater-like hilum with a raised punctation at the point of stalk attachment. The spores do not readily fall off the stalks unless they are mechanically disrupted. While this species is morphologically similar to P. mycophaga and the closely related flagellated species, Planoprotostelium aurantium, it differs from both in its lack of pigmentation, its inability to feed on yeasts, and in the structure of the mature sporocarp. Therefore, it is placed in a new genus in a revised family Protosteliidae.

Key Words:

• amoebae
• mycetozoans
• slime molds
• systematics
• taxonomy