Paradiachea caespitosa

paradiachea-caespitosa
Paradiachea caespitosa 31 Dec. 2016

If you’re fortunate enough to live in a place where daily inspection is possible, a wonderful aspect of searching for slime moulds is the anticipation; just what will the plasmodium become?
On December 12 2016 I noticed a white plasmodium on big tree stump (a hotspot of slime mould activity) so I took a series of photographs to monitor its transformation.

As the photos indicate, the plasmodium gradually changed colour from creamy white to pale yellow before rain halted its development. The only fruiting bodies worth collecting were in the crevice of the stump, where they’d presumably been sheltered from the rain. Despite being in poor condition they could be identified as  Paradiachea caespitosa. Like other members of the Order Stemonitales  Paradiachea caespitosa has an aphano (invisible) plasmodium, but one that clearly becomes pigmented before the fruiting bodies form.

On December 31 2016 the same species (could it be the same ‘individual’?) appeared under big tree log, a more sheltered location about a meter away. The fruiting bodies were in good condition and collected before invertebrates (mainly beetles) had started feeding on and laying eggs into the spore mass (see photo above).

On January 26 2017 I saw a yellow plasmodium on the fibrous bark of a living eucalypt (Eucalyptus delegatensis). From a distance it resembled the bright yellow plasmodium of Fuligo septica when it first appears. However, on close inspection the plasmodium was a mass of closely packed immature fruiting bodies and the next day my suspicions were confirmed. After an absence of several years, this was the third appearance of P. caespitosa this summer. Furthermore, this was the first appearance on a living substrate; all previous collections were from large logs or stumps.

Paradiachea caespitosa has closely-packed (caespitose) sessile, club-shaped sporangia to 1.5 mm high. Its extremely thin iridescent peridium reflects different colours: the December 31 collection was predominantly silver with some blue reflections;  the collection on January 26 was gold, purple and blue.

P. caespitosa has a thick columella with a woody appearance to which is attached the capillitium along its full length. The capillitium is sparsely branched with bifurcating tips. The spores are 10-13 microns with scattered warts.

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