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Myxomycota – the plasmodial slime
moulds

The plasmodial slime moulds are wall-less organisms
that consist of a multinucleate network of protoplasm
(the plasmodium; Fig. 2.36) exhibiting rapid, rhyth-
mic surges of protoplasmic streaming. These organisms

are commonly seen in the autumn on moist rotting
wood, on senescing fungal fruitbodies and on similar
organic substrata where bacteria are abundant. They
engulf bacteria and other food particles by phago-
cytosis. The plasmodium typically develops within a
substrate but then migrates to the surface in response
to nutrient depletion and the whole plasmodium con-
verts into fruiting structures (sporangia) containing

44 CHAPTER 2

Fig. 2.36Myxomycota. (a) A plas-
modium of Physarum polycephalum
growing on an agar plate. Note how
the plasmodium, which was inocu-
lated in the center of the plate, has
migrated towards the margin, where the
protoplasm has amassed. (b) A decay-
ing bracket fungal fruitbody (about
15 cm diameter) completely covered
by cream-colored sporing structures
of the myxomycete Fuligo septica. (c)
Mature sporangia of the slime mould
Physarum cinereumon a grass blade
about 4 mm diameter; many of the
sporangia have opened to release the
dark gray spores. (d) Immature, pink
sporangia of Lycogalaon the surface of
rotting wood; each sporangium is
about 1 cm diameter. (e) Similar spo-
rangia 5 days later, when the spo-
rangia had matured, turned gray, and
consisted of a thin papery sac that
ruptured to release the spores.

(a) (b)

(d) (e)

(c)

Fig. 2.35The life cycle of Dictyoste-
lium discoideum. (Courtesy of Florian
Siegert ©. From: http://www.zi.biologie.
unimuenchen.de/zoologie/dicty/
dicty.html)

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