''Ceratiomyxa'' is a genus of plasmodial slime mould within the Eumycetozoa, first described by Pier Antonio Micheli. They are widely distributed and commonly found on decaying wood. The plasmodium often appears as white frost-like growth or thin watery layers on wood. Pillar or wall-like sporangia bud from the plasmodium and develop spores that undergo multiple divisions before they release flagellated

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or ...

s. The zoospores will then pair off, undergo plasmogamy, and form zygotes that will later form new plasmodia. The genus currently contains 4 species. The most notable member is ''Ceratiomyxa fruticulosa,'' a slime mould found in most parts of the world. Other known species of ''Ceratiomyxa'' are mostly found in the tropics.

Etymology

''Ceratiomyxa'' comes from the Latin word ''ceratus'' meaning "waxed" and the

ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

word ''myxa'' meaning "mucus".

History of knowledge

''Ceratiomyxa'' was first described under the name ''Puccinia ramose'' (later revised to ''Ceratiomyxa fruticulosa'') in 1729 by Pier Antonio Micheli, a pioneer of mycology. In 1805, Albertini and Schweinitz described 2 more species in the genus, ''C. hydnoides'' and ''C. porioides''. However, because ''Ceratiomyxa'' species can take a variety of different forms, many forms first described as species are later considered synonyms. This includes ''C. hydnoideum'' and ''C. porioides'' which are now often considered synonyms of ''C.fruticulosa''.^1,2 ''Ceratiomyxa'' was first placed in the subclass Ceratiomyxomycetidae of the class Myxomycetes by Martin and Alexopoulos in 1969, but was later moved to subclass Protostelia of the class Eumycetozoa by Olive in 1970.^1,2

Habitat and ecology

''Ceratiomyxa'' is commonly found on rotting wood. Large logs and stumps are cited as ideal substrates for growth, although smaller colonies can also be found a tree branches. The ''Ceratiomyxa'' collection of Henry C. Gilbert has specimen growing on various evergreen coniferous trees (''Pseudotsuga''), elm (''Ulmus''), maple (''Acer''), oak (''Quercus''), ''Tilia'', and willows (''Salix''). A specimen collected by F. O. Grover was found growing on a burlap sack.¹ Species of ''Ceratiomyxa'' can be found world-wide. ''C. fruticulosa'' is the most common species and has a cosmopolitan distribution. ''C. morchella'' and ''C. sphaerasperma'' have only been recorded in the tropics.³

Morphology

Plasmodium: Net-like or thin layer enveloped in mucous. Often translucent or white in colour but can also be tinted slightly yellow, pink, or blue-green. The protoplasm within the plasmodium can be seen flowing, resting, and resuming flow in the opposite direction. This occurs in intervals of approximately 40 seconds. Protoplasmic flow slows as the sporangia develop and halt completely during mitosis.¹ Sporangia: Can be found in many different forms. Common forms include: * Simple pillar: Pillar-like projections. In some species, pillars expand at the base and fuse to form a layer of plasmodium * Fruticulus: Clusters of finger-like projections that are usually undivided¹ * Arbuscula: Branched resembling small trees. Spores develop on branch surfaces * Filiforme: Long and slender pillars * Porioides: Net-like formations of walls. Spores develop on sides and edges of wall Spores: The spores are round or oval globules individually attached to stalks sprouting from sporangia. Spores vary in size (8-13 µm in diameter). The spore walls are thin and transparent. Spores appear grainy and may have some vacuoles which are often near the perimeter or surrounding the nucleus. The nucleus within the spore is about 3 µ in diameter.¹ Swarmcells: Oblong with either one long flagellum, one long and one short flagellum, or 2 long flagella. The flagella may occur together or at opposite ends of the cell. Upon emergence, the swarmcells are 6-8 µm in length and can develop to around 12 µm in older cells.¹

Life cycle

''Ceratiomyxa'' plasmodia is diploid and can often be found emerging from rotting wood and spreading into a thin layer. The plasmodium then fruits to form sporangia: erect pillar or wall-like structures. The sporangia mature in about six hours. Many small stalks emerge from the sporangia to form protospores. Meiosis then begins in the protospores. Synapsis of the chromosomes in prophase is achieved at this stage. After the stalks have fully elongated, a thin transparent wall is secreted around the protospores to become spores. Spores take approximately 24 hours to mature. The first meiotic division is then completed in the spores followed by a second meiotic division which leaves the spore with 4 nuclei. After dispersal, these four-nucleate spores germinate and naked protoplasts emerge. The protoplasts take in water upon emergence and enlarge to about 3 times the size of the spore from which they emerged. The protoplasts then form short thread-like filaments that later retract back into round globules. In some cases, the protoplast skips the thread phase and remains isodiametric. The nuclei then migrate to four points of a tetrahedron and the protoplast cleaves into a tetrad of lobes. Soon after, the tetrad undergoes mitosis and splits again into an octette of haploid cells. Each cell releases a swarmcell with either one long flagellum, 2 unequal flagella, or 2 long flagella. The flagella are apical and whiplash type. The swarmcells may then lose their flagella and become asexual myxamoebae or undergo syngamy in pairs to produce a diploid zygote.^1,2

List of species

Genus ''Ceratiomyxa'' currently includes four species: * '' Ceratiomyxa fruticulosa'' Micheli, 1729 * '' Ceratiomyxa sphaerosperma'' Boedijn, 1927 * '' Ceratiomyxa morchella'' Weldon, 1954 * '' Ceratiomyxa hemisphaerica'' Olive and Stoianovitch, 1979

References

¹ Gilbert, H., C. 1935: Critical events in the life history of ''Ceratiomyxa.'' Am. J. Bot. 22: 52-74 ² Olive, L. S. and Stoianovitch, C. 1979: Observations on the Mycetozoan genus ''Ceratiomyxa:'' Description of a new species. Mycologia. 71: 546-555. doi: 10.2307/3759064 ³ Rojas, C., Schnittler, M., Biffi, D., and Stephenson, S. L. 2008: Microhabitat and niche separation in species of ''Ceratiomyxa.'' Mycol. Soc. Am. 100: 843-850

References

{{Taxonbar, from=Q1054642 Amoebozoa genera Eumycetozoa