Microbes, fungi, maggot fern

hyphae in maggot fernFungi are supposed to have been around since the Proterozoic [1] but have been preserved as fossils only under conditions of rapid silicification, as in the Lower Devonian habitat turned into the Rhynie chert with lots of well-preserved fungus remains. Fossil fungi are rare in the Permian cherts of the Döhlen basin. (See Permian Chert News 14.)  Perhaps some hyphae are easily overlooked if poorly preserved, or they are mistaken for microbial filaments or plant hairs.

Fig.1: Curved pinnules of the "maggot fern" (Scolecopteris) in a row, cut such that the cross-sections with sporangia and the sheltered spaces with thin hyphae and thicker hairs are seen. Width of the image 8mm.

A rare combination of microbes, fungus hyphae, and hairs is seen in Fig.1, which shows an inclined cut of a row of curved maggot fern pinnules. Apparently these pinnules are even more curved than those seen in side view in Permian Chert News 1. Owing to the curvature, the pinnules appear nearly as cross-sections above (see Permian Chert News 15) and provide a look into the sheltered space between the fringes of the lamina below. The pale empty sporangia of the fern may be easily recognized as such. The thin fungus hyphae are easily seen against the dark background if not covered with microbes too much. The hairs sparsely distributed at the lower side of the pinnules are much thicker than the hyphae (Fig.2).
hair on pinnule
Fig.2: Detail from Fig.1, near image centre, hair emerging from the lamina of the pinnule, with thin fluffy microbial cover, glistening spot where the cover probably had been scratched off before silicification so that the smooth reflecting surface appeared. Image width 0.7mm, lamina thickness 0.25mm.

fungu spheres

The microbes involved here do not form filaments by themselves but coatings and floccules without definite shape but with sharp boundaries against the surrounding water.
The yellow, red, and brown colours are provided, as usual, by iron oxides. The bluish hue on the left of Fig.1 is not due to a mineral pigment but to light scattered on tiny precipitates in the clear chalzedony.

Fig.3: Slightly inclined lengthwise section of a largely decayed root surrounded by a thick fluffy microbial coating and with numerous spherical chlamydospores of some fungus whose thin hyphae stand out against the dark background. Width of the image 5mm.

Like hyphae, chlamydospores are seldom seen in Permian cherts but are common fossils in the Rhynie chert. The assemblage of numerous chlamydospores in Fig.3 is the only find of this type in the Permian cherts of the Döhlen basin but similar assemblages are known from the Rhynie chert. (See Rhynie Chert News 104, 115.) Diameters of the spheres in Fig.3 are up to 0.3mm, thus being comparable to those in
104 . Without detailed investigations it would be rather difficult or even impossible to assign the hyphae and chlamydospores to a certain fungus clade.  
Another problem remains: Why did this fungus, which is a tangle of thin hyphae, choose to produce bulky chlamydospores in large numbers and to place them clustered together ? One may assume that there must be a reason which has to be found out.

It may be appropriate here to warn against a potential misinterpretation: Spherulites must not be mistaken for chlamydospores. Two of such, size 0.34mm, are half seen in Fig.1 between the first and second pinnule.

Samples: Döhlen basin, Hänichen, Käferberg.
Figs.1,2: H/321.1, 0.85kg, 1999,
Fig.3:  H/333.2, 4.65kg, 2001.

[1] T.N.Taylor, M. Krings, E.L. Taylor: Fossil Fungi. Elsevier 2015, p.28.

H.-J. Weiss       2017
Scolecopteris pinnule cross-section, Sardinia Permian Chert News 17

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