Golden moldies: treasured by aficionados, fungi remain mostly anonymous subjects of distant kingdoms, underappreciated for their role as recyclers

Natural History, June, 2004 by George W. Hudler

Fungi tend to be inconspicuous, growing under a log, on a peach skin, inside a building wall. The gallery of photographs on display here highlights a few strikingly beautiful species, as visual reminders that there are entire kingdoms of organisms, often neglected, that are not to be overlooked. For one thing, fungi are extremely sensitive to the environment. Whenever people get alarmed about the stability of the Earth's ecosystems, from deforestation to global warming, the threats to plants and animals are what invariably spring to mind. But behind the scenes are the untold millions of fungus species whose fate is bound up with the health of their sometimes more charismatic hosts--and vice versa. Fungi play a vital role in the web of life by taking apart the complex but specialized molecules assembled by plants and animus and recovering the basic molecular building blocks in a form that future generations can use. Fungi are some of our best recyclers.

Fungi were once united as a taxonomic kingdom by such common features as nucleated cells, the absence of chlorophyll, and reproduction by spores. Until the late 1980s, for instance, students burrowed into mycology textbooks that described "old" fungi (like your traditional mushroom) right next to chapters on such groups as slime molds that usually don't even have cell walls.

Recent rapid advances in molecular systematics have shaken the fundamental bases of fungus classification. Now, under the overarching heading of the Fungi kingdom, or true fungi, are grouped the phyla Chytridiomycota (one-tailed spores), Zygomycota (pin molds and their diverse relatives), Ascomycota (sac fungi), and Basidiomycota (club fungi). Similarities in critical nucleic acid sequences and morphological features unite them all. The Oomycota (two-tailed spores), in contrast, are more closely related to algae than to fungi. The Myxomycota, or slime molds, will probably be assigned to their own separate kingdom. Fortunately; many reputable scientists still speak about "fungi" colloquially. Thus, just as botanists and nutrition experts unabashedly refer to fruits such as cucumbers and peas as vegetables, so it is acceptable to blame the mid-nineteenth-century Irish potato famine--caused by one of the Oomycota, Phytophthora infestans--on a fungus.

What hasn't changed is that many people are still fascinated by fungi, drawn by their mystery, their taste, or their fantastical shapes. For some fungi, reproduction proceeds by way of mushrooms, which bear spores on their gills, or by way of puffballs--the relatively large structures that produce millions of spores in dry, powdery masses, to be whisked away by a breeze. For others, spores come in slimy masses, often with characteristic odors or tastes that attract insects. And still other fungi have evolved to take advantage of the energy released by splashing rain or falling sticks to improve their chances for continued survival of their species.

To one who has made a career of introducing young minds to the world of the fungi, I am constantly reminded that appearance is what causes newcomers to stop and look and learn and then learn some more. It seems unlikely that someone can just walk away, after seeing these specimens, without some curiosity about their structure or their role in the environment--fungi, after all, are remarkably adept at using their spectacular forms to spread around and set up for an extended stay.

This ghostly white specimen is Clavaria fragilis, a coral fungus--so named for its resemblance to the skeletons of undersea creatures. Its single-stalked fruit body is much like the surface of a mushroom gill, rich with spores. Long-term survival of a C. fragilis colony requires that the germinating spores soon find new roots of a compatible plant--often a tree or shrub. Together the fungus and plant form structures known as mycorrhizae (from the Greek words mykes, of "fungus," and rhiza, of "root"), which are essential for the survival of both partners.

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You might forget you are on land as you stoop for a closer look at Calocera viscose. It looks for all the world as if it should be among the 125 species of coral fungi because its reproductive bodies appear so similar to marine coral. But don't be fooled; the so-called yellow tuning fork is actually a jelly fungus coated with microscopic spore-bearing cells, a feature that distinguishes the jelly fungi from all other fungi in their kingdom. Yellow tuning forks occur on the forest floor, where they digest decaying pine and spruce trees.

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Stinkhorns such as this Anthurus archeri (also known as Clathrus archeri) come in all shapes and sizes, but they all give off the odor of rotting flesh. The source of the odor--enough to send even the most ardent picnickers packing--is the slimy, greenish brown matrix (seen here on the arms of the stinkhorn), which houses the spores. Some members of this group are colored bright pink to red, including A. archeri, and send out particularly strong signals: flies accustomed to dining on animal carcasses descend on the spore bodies with gusto. After they eat their fill, the insects do their part by carrying spores away on their legs or in their gut to other locations.