An entry from Cora den Hartigh today. Cora writes:
Here is a capture by Anne Elliott (annkelliott@Flickr) of a very small, exquisite organism in a woodpile near Millarville, Alberta (original 1 | original 2). Tiny wonders in the most unexpected of places! Thank you for your sharp eye.
Stemonitis axifera is a cosmopolitan slime mould, pictured here in both its dewy pink youth and rusty-brown spore-producing stage. In the past, being a slime mould meant being associated with mushrooms. Today, slime moulds are classified as multicellular or multinucleate spore-producing amoebas. The University of California, Berkeley has a very useful Introduction to the Slime Molds, where they clearly outline the difference between the multicellular and multinucleate. To illustrate, check out some of these micrographs!
The morphology of slime moulds might seem bewildering, but this delicately coloured glob is simply a bundle of developing, tubular sporangia sprouting from minute, shiny black stalks. When food is scarce, Stemonitis axifera (and other slime moulds) are able to conglomerate their various nuclei and produce sporangia, much like a fungus. Spores from the sporangia are dispersed, sometimes by slugs or other agents, to new habitats where they grow into new amoebae. If they are not in this fruiting stage, slime moulds are very difficult to find, as they creep along the substrate sensing chemicals in the air that might lead them to their favourite foods: bacteria or yeasts on dead and decaying plant matter. In the case of Stemonitis axifera, this is almost always a decaying log.
At the initial stages of conglomeration (the first photo), Stemonitis axifera is a favourite snack of mantle slugs (Philomycus), which snoop about on the exposed surfaces of logs after dusk. The slugs are in a bit of a race against time, though, because once Stemonitis axifera begins to mature, it only takes about 20 hours to complete its life cycle! In 2008, a French study followed a Stemonitis axifera specimen in situ with a series of photographs and recorded the life stages: “eight hours for the induction of sporangia, columella and stalk development, six more hours for rusty-red pigmentation and maturation of sporocarps and a final six hours until spores began to discharge.” By the time of Anne’s second photograph (when the sporangia are rusty-brown), the slugs lose interest!
Although somewhat unrelated, a fascinating side note: slime moulds are, of course, rare in the fossil record due to their ephemeral nature and lack of vasculature, not to mention the transience of their substrates (dung, moist decaying matter and the like). Nevertheless, some slime moulds have been discovered trapped in Baltic amber! An Archaic Slime Mould in Baltic Amber is a 2006 paper by H. Dörfelt and A.R. Schmidt documenting this discovery from Kalinigrad, complete with some charming photographs of ancient slime moulds!