Common Name: Scrambled Egg Slime, Dog Vomit Slime – Slime is any soft, gelatinous and formless mass – a descriptive term that has no biological specificity. Slime is an abbreviated form for the more descriptive full name slime mold; it is in a sense both slime and mold. The color and texture are metaphors for scrambled eggs if yellow and dog vomit as it turns a tan-brown color with age.
Scientific Name: Fuligo septica – The generic name is Latin for ‘soot’ and the species name is derived from septicus, Latin for ‘putrid’ (as in septic tank). The overall intent is to convey a black, particulate substance associated with the putrescence of bacterial decomposition; F. septica starts out yellow and gradually turns black with age – which may be why the genus is named ‘soot,’ which must surely be black.
Potpourri: Like the centaurs and satyrs of Greek mythology, slime molds are an incongruous combination of two separate and distinct physiologies, a fact that has confounded their proper classification within the hierarchical confines of taxonomy. Even the slime mold name conveys a notion of some sort of unholy union; a dichotomy of uncertain provenance. Slime molds start out as spores from a fruiting body that is fungal in form and function which would align them with the fungi. When the fungi were afforded full kingdom status in the late 20th century, slime molds were placed in the Phylum Myxomycota (Greek for ‘mucous fungi’ a suitable synonym, essentially biological slime). It is for this reason that the slime molds are included under the rubric of mycology. However, when the fungus-like spores germinate, they do not form the filamentous hyphae of the fungi, but rather they transmogrify to single-cell nucleated amoeboids that move about with pseudopodia just like any other amoeba of the Kingdom Animalia. So slime molds are slime in the sense that they are viscous and mobile and they are mold in the sense that they are small fungi. In the continuous evolution of our understanding of the taxonomy of biological relationships, slime molds and other mostly unicellular, eukaryote (having a nucleus) anomalies gave rise to an interim taxonomy of things that were both plant and animal and therefore neither; they were placed in the Kingdom Protista. Recent advances in biology, genetics and evolutionary development have discombobulated the physical structure based taxonomy of Carolus Linnaeus – a process that is far from over. In the most recent rearrangement known as the six-kingdom model, the slime molds are in the Kingdom Protozoa (Kingdom Amoebozoa in some texts), the mobile amoebae products of the fungal spores having dominated the genetic phylogeny. To afford a measure of consistency, the slime molds retain their euphonious group name, as they are now in the Class (vice Phylum) Myxomycota, even though the kingdom has changed. This doesn’t make the slime molds any less peculiar.
The mobile unicellular, amoeboid animalcules afford the slime molds their quixotic life cycle. They are phagotrophic, feeding on the even smaller bacteria for nutrition, the characteristic that aligns them with the Protozoa over the Fungi. The amoeboids can be in one of two forms: a myxamoeba that moves by the extension of the membrane wall (false foot or pseudopod) and an elongated form called a swarm cell with a whip-like flagella from one end or the other (or both) to enhance propulsion. In the absence of nutrients, the amoeba is transformed into a thick-walled protective sphere called a cyst in which state it can persist for some time. Under nutrient rich propitious conditions, two amoebae or swarm cells of compatible mating types (like the fungi, there are no recognizable male or female sexes) fuse together, the two haploid (n) gamete cells forming a diploid (2n) reproductive zygote. The resulting organism is called a plasmodium, the quintessence of the slime mold. The plasmodium is a single large cell that undergoes mitosis (nuclear division) without cell division, so that a single cell that starts with the two nuclei of the original haploid gamete amoebae can multiply geometrically (2,4,8,16) up to millions of nuclei all within a single cell membrane. Plasmodia grow, like their amoeboid precursors, by eating bacteria in addition to yeasts (which are fungi) and algae (which are plants). In this form they can get quite large, able to engulf and ingest increasingly larger prey. It is the growth of the plasmodia that characterize the slime molds, as the growth is coupled to movement. According to Michael Carlisle et al in The Fungi, 2nd Edition, this streaming is observable in a microscope that shows “a torrent of protoplasm moving in one direction at speeds of up to one millimeter per second for about a minute.” Curiously, the flow then reverses, like the Greek strophe, flowing in the opposite direction for about the same duration – a pulsating mass. The efficiency of consumption, movement and growth is such that a slime mold can grow to twice its original size every 8 hours.
A large, moving, pulsating and growing blob of unknown origins has, on at least one documented occasion, resulted in high anxiety that was quite possibly triggered by association with the 1957 movie “The Blob” in which a formless mass terrorized a small town killing several people. The incident in question occurred in Garland, Texas, a small town near Dallas in the backyard of Mrs. Marie Harris. According to an Associated Press article on 30 May, 1973 “It’s something right out of an after-midnight television horror movie – a mysterious, encompassing ooze, dubbed ‘The Blob.’ – So far it appears to be friendly.” The Dallas Times Herald first reported the incident quoting Mrs. Harris as asserting that “it has multiplied itself 16 times over in two weeks…blackish mucous…reddish with thick bub-gigs (sic) on top…foamy like shaving cream.” A neighbor named Edna Smith reported that it had climbed a telephone pole. The origins of the tale have become apocryphal in the retelling, a mycological urban legend. According to the Audobon Field Guide to Mushrooms, the fire department was called and used high pressure water, which encouraged it to grow even larger, at which point the “people demanded that the governor call in the National Guard.” The culprit is identified as a relative of many-headed slime (Physarum polycephalum), although this is also subject to conjecture. The International Herald Tribune of 1 June 1973 reported that “Dr. Fanny Hurst, a botanist at Baylor University” determined that “it could have been a Fuligo … usually seen in the yellow, pulsating form Mrs. Harris described to newsmen.” That it is was more likely to have been scrambled egg slime is affirmed by Miller and Everhart in “Importance of Myxomycetes in Biological Research and Teaching” (Fungi Vol. 3 No. 1), who noted that “These yellow blobs were present for a three-week period and the fruiting bodies were finally identified as Fuligo septica but not after concern that a lawn disease or an alien source had invaded the site.” The demise of the dreaded yellow blob was no less mundane. Again from the 1973 Associated Press article: “Mrs. Harris …recounted ‘I got a call from a woman here in Dallas who said that tobacco mixed with water was an old-time remedy for killing insects in gardens. I figured I had nothing to lose and tried it. It started to dry up and that’s what’s left.’ She pointed to some white, crusty material at the edge of her garden. So much for the original blob.” Like all other slime molds, it probably ran out of food and sporulated.
The study of slime molds has lagged that of other organisms, their sub-rosa habitat under tree bark and leaf litter seldom rising to the notice of early botanists (or zoologists for that matter), the blob story notwithstanding. The slime molds like F. septica that form a plasmodium are appropriately called plasmodial slime molds to distinguish them from the other two types of slime mold amoebozoans: the cellular slime molds (dictyostelids); and the protostelid slime molds (protostelids) – primarily epigeal soil dwellers and, though ubiquitous, are nearly invisible without magnification. The larger plasmodial slime molds do on occasion draw attention (again the blob story). According to Stephenson in The Kingdom Fungi, “in writings from the ninth century attributed to the Chinese scholar Twang Ching-Shih, there is a reference to a certain substance kwei hi (literally ‘demon droppings’) that is of a pale yellowish color and grows in shady damp conditions.” While a somewhat more scatological description, this is clearly referring to the subject slime, which is not wanting for metaphor. The leitmotif of offal seems to be as universal as is the global F. septica. In Scandinavia, it is associated with the superstition of the witch’s troll cat, a chimerical beast that got its milk either directly from cows or stole it from households. The yellow slime mold was attributed to troll cat vomit and purportedly used by witches to spoil the milk of those they cursed. As testimony to the diversity of cultural norms, the Native Americans from Cofre de Perote in Veracruz, Mexico call F. septica “caca de luna” meaning ‘moon scat’ but treat it more like the scrambled eggs of North American linguistics. They harvest it, cook it with onions and peppers and eat the resultant concoction on a tortilla, reportedly with (gustatory) relish.
The plasmodium of a slime mold continues to grow only so long as there is nutrition. If adverse conditions prevail, a dormant state called a sclerotium forms to sustain the germ of life through the downturn. When conditions promoting reproduction prevail, the plasmodium gives rise to fruiting or spore-producing, bodies that resemble (though are much smaller than) those of the fungi. Plasmodial slime molds are taxonomically classified according to one of four basic types of fruiting body: sporangium, aethalium (basically a mass of fused sporangia), pseudo-aethalium, and plasmodiocarp (a vein from the plasmodium). Fuligo septica forms a massive aethalium (the second type), which gives it a prodigious spore production capacity – billons of ~7 micron spinulose spores released to the wind. Due to its propinquity to human habitations, its ubiquity, and the spiny tenacity of its spores, it has been subject to assessment as an allergen. A study conducted by Rockwell et al and reported in the Journal of Allergy and Clinical Immunology found that 40 percent of the 250 participants had an allergic reaction to F. septica and concluded that “Individuals hypersensitive to mold spores should use face masks to avoid contact with slime mold spores.” A second area of scientific evaluation of the properties of F. Septica is in bioremediation – not an uncommon consideration for fungi, which extract minerals from the environment as a matter of physiology. At the International Symposium of Metal Ions in Paris in 2008, a Finnish researcher reported that Fuligo septica (commonly called paranvoi in Finnish – this translates roughly to ‘belief being,’ thought to have something to do with the theft of butter – which is likely similar to the other Scandinavian superstition of the troll cat of the witch) contained between 2,000 and 22,000 mg/kg (which is the same as ppm) of zinc. This was attributed to the fact that the yellow pigment fuligorubin A binds to zinc. The potential of Fuligo septica for reclamation of metal-contaminated soils awaits demonstration.