Macroplasmodium

After the grim weather yesterday I was in desperate need of a couple of hours immersing myself in the delights of Old Sulehay Forest, with its twisted coppice stools and richly fragrant scent of humus and rotting leaves. There were some excellent fungi on dead wood, including the largest and most vividly coloured example of Jelly Rot that I've ever seen. I spent most of my time away from the paths and so was lucky to see a fallow deer stag and a muntjac, while buzzards mewed overhead and a low-flying raven cronked as it went over. It always amazes me that neither of these species occurred in the Peterborough area when I first moved here in 1985.

During my walk I found four different species of slime-mould -  this was the most spectacular of them.. Slime-moulds have a complex life cycle and this stage is a multinucleate amoeboid mass of protoplasm, called the plasmodium. Favourable temperature, abundant moisture and food favour its growth, movement and reproduction. In many cases the young diploid plasmodia may combine with zygotes or other plasmodia of the same species or a number of zygotes may coalesce to form a single larger plasmodium. In all these cases, the union involves the fusion of their cytoplasm only. There is no fusion between the nuclei. Eventually the plasmodium may become a massive structure called the macroplasmodium.

This very extensive plasmodium of the species Badhamia utricularis is about to enter the reproductive phase. The amoeboid life ceases. The slime layer dries. The quiescent plasmodium thickens. The diploid protoplast concentrates at a few points forming a mound like structure. The latter grows into a stalked sporangium, which in this species looks rather like bunches of tiny grapes (see extra on my entry of 30/12/2019).  

The diploid protoplasm or of the sporangium cleaves into numerous young spores each of which has a diploid nucleus.The diploid nuclei of the young spores undergo meiosis to form meiospores. When mature the meiospores are released and dispersed by wind. On falling on a suitable substratum and under favourable conditions, the meiospore germinates to release swarm cells or myxamoebae which fuse in pairs to form the zygote in which the diploid condition is re-established.