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Eurotium


An ascomycete characterized by whitish to bright yellow spherical fruiting bodies (cleistothecia) containing spherical asci which in turn each enclose eight colourless ascospores. The ascospores are oblate (like a flattened sphere) and may have equatorial ridges, thus resembling pulleys. Species of Eurotium grow best in dry situations and are usually cultivated on media high in sucrose or glycerine. They are common in homes, stored grains, and rodent dwellings.

The three photographs at top are of a strain of Eurotium rubrum found growing on an old pita bread in a New Brunswick home. The bright yellow-orange colony is typical of Eurotium species where the bright yellow cleistothecia greatly outnumber the green masses of conidia. The green colony at left is a species of Penicillium, probably P. chrysogenum. The middle panel is an enlargement of the colony showing the yellow cleistothecia nestled among the red hyphae characteristic of E. rubrum. The right panel shows a group of spores. The darker, roughened spores at the right and top of the picture are conidia of the Aspergillus anamorph of the fungus. The rest of the spores are ascospores, which are shaped like minute hamburgers. In common with hamburgers, ascospores of Eurotium species tend to come to rest on a top or bottom rather than on a side. Thus most of the ascospores look circular. However, two of these are lying on their side and thus have the elliptical outline of a hamburger as viewed by someone about to bite into it. The group of ascospores that are slightly out of focus are still inside an ascus, although the ascal wall cannot be seen. All of these features can be seen more clearly in the drawing at right. The coiled structure in the drawing is an ascogonial coil, discussed in greater in the discussion of the Sordariomycetes.

Classification: Trichocomaceae (Eurotiales). Anamorph: Aspergillus. Ref: Blaser 1976; Klich and Pitt, 1985; Raper and Fennell 1965


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