Hemitrichia

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Hemitrichia
Hemitrichia calyculata 113390.jpg
Hemitrichia calyculata
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Phylum: Amoebozoa
Class: Myxogastria
Order: Trichiales
Family: Trichiidae
Genus: Hemitrichia
Rostaf.

Hemitrichia is a genus of slime molds, of the family Trichiidae, found within the order Trichiida. It was first described by Josef Rostafinski in 1873 and remains a well-defined genus of the slime molds. Hemitrichia species exhibit either plasmodiocarp or sporangium fruiting bodies, both of which are well-known and recognizable slime molds seen on multiple continents. The genus includes Hemtrichia serpula, known as the pretzel slime mold, an iconic and widespread species that has been used to examine speciation in slime molds.[ citation needed ]

Contents

Etymology

Hemi comes directly from the Greek prefix hemi, meaning “half”. [1] Trichia is combination of the Greek trichios, which refers to hair or hair-like structure and –ia, referring to a condition, [1] leading to –trichia being the condition of having hair. Hemitrichia therefore refers to the condition of partially having hair.

Josef Rostafinski described Hemitrichia in the family Trichiaceae, along with another genera Trichia. Trichia was described as having numerous capillitium threads, which are free and tapered at the ends. [2] Hemitrichia is described as having capillitium threads that can either be free or fused into a net. [2]

History of knowledge

As in all members of the Trichiida order, the structure of the capillitium plays a major role in identifying and defining the different families and genera. The presence of a net-like capillitium is likely the most defining and recognizable feature of the genus Hemitrichia, as it has been mentioned by almost every author in his or her description of the genus. It was first described by Josef Rostafinski in his 1873 book “Versuch eines systems der mycetozoan”. [2] Rostafinski places Hemitrichia as one of two genera under the family “Trichiaceae”, the other being Trichia. [2] Rostafinski describes the genus as having “[c]apillitium tubes fused into nets, free or with single tapered ends trapped between stalk contents”. [2] The genus has also previously been referred to as “Hemiarcyria” by Fries in 1829 and as “Hyporhamma” by Corda in 1854. [3]

In 1922, Thomas MacBride published his second edition of The North American Slime Moulds, the monograph in which he first describes the Trichida order. In this book, the genus Hemitrichia is described as having the “[c]apillitium a tangled net of more or less branching and [cross-connecting] fibres” as well as detail about the capillitium threads, which are “conspicuous spirally winding bands or ridges”. [3] “The Myxomycetes” by G.W Martin and C. Alexpoulous, a monograph considered to be one of the most important and influential works on the plasmodial slime molds, [4] describes the genus as having a capillitium with tube-like threads that are connected into a net, with either free or connected free ends, and decorated with several spiral bands. [5]

Martin and Alexpoulous’ monograph also mentions that the genus includes some species that would also fit well under two other Trichia genera: the Arcyria and Trichia. [4] In MacBride's book, Hemitrichia represents an intermediate between Arcyria and Trichia, and he notes that the presence of the net formation in the capillitium was similar to Arcyria, while the spiral bands are a distinct feature in the Trichia genera.

Currently, Hemitrichia remains a well-studied slime mold genus, with over 40 described species found on multiple continents. Very little molecular research has been done to fully explore the phylogeny and evolution of the slime molds. The majority of the field has relied on morphological features, which often only emphasize the plasmodium life cycle of the organism. [6] Further molecular research into slime mold taxonomy could reveal more information on the family tree and evolution of Hemitrichia.

Habitat and ecology

The majority of Hemitrichia species can be found on rotten or dead logs [5] in lowland forest. Species of Hemitrichia have been found on four major landmasses: Asia, Europe, North America and South America. [6] Of the 26 recognized species, 13 have been found in the Neotropical Region. [7]

Description of organism

Hemitrichia is one of six current genera within the family Trichiaceae within the order Trichiida. Trichiida are endosporous Myxomycetes, meaning their spores are held within an acellular structural wall. [4] They are members of the superorder Lucisporidia, which are the brightly coloured Myxomycetes that lack a feature called the columella, which is an extension of the spore stalk through the structure that holds the spores. [8] Members of the family Trichiaceae are described as having sessile or stalked fruiting bodies, and either hold spores in a plasmodiocarpic or a sporocarpic vessel [9] (see Life cycle). Family members also have tube-like capillitium that are hollow and can have “decorations” such as spirals or spines. [7] In the genus Hemitrichia, these tube-like capillitium threads will form an “elastic net”. [5] These nets will take on the colour of the spores within them, which ranges from yellow to red as is expected in superorder Lucisporidia, or the brightly coloured slime molds. [5]

Life cycle

Members of the Hemitrichia follow the typical plasmodial slime mold life cycle, which exhibits two main stages as well as possible sexual reproduction. [4] Slime molds spend a period of their life cycle as a myxameoba or a swarm cells. [4] These cells are able to exist as either amoeba or flagellates depending on the conditions the cell experiences, and are hence known as amoeboflagellates. The amoeba form is preferred for terrestrial environments, while the swimming ability of flagella is preferred in a wet environment. These amoeboflagellates also contain a single nucleus, which at this stage in the life cycle is haploid. Under adverse conditions, such as a poor environment, overcrowding or the presence of toxins, these cells can encyst into small, walled cysts that can return to the amoeboflagellate form if conditions improve. [4]

The amoeboflagellated stage will undergo sexual reproduction, as two cells fuse to create a diploid cell. This cell will then undergo many rounds of nuclear division without any cellular division, resulting in a rapidly growing, membrane-bound cell with multiple nuclei known as the plasmodium. [4] Fusion with more diploid stage cells, and even with other plasmodium of the same species, [4] will continue to increase the size of the plasmodium. These macroscopic forms of the slime mold are the most well-known and best-studied stage of the life cycle. The plasmodium feeds on bacteria, other microorganisms and can even cannibalize other slime molds. [4] The massive cytoplasm contains multiple nuclei, contractile vacuoles, mitochondria and food vacuoles found on the peripheral edge of the plasmodium. [4] This plasmodium stage usually exists from late spring until early fall. [5]

Plasmodium will then begin to form fruiting bodies, which will hold the haploid spores. The spores will develop within a walled structure, and when they are mature they will be released to disperse through multiple means. Wind has often been cited as the main means of dispersal, but other modes such as sticking to insect legs have been proposed. [10] Hemitrichia species can have two kinds of fruiting bodies. [9] One kind is known as a plasmodiocarp. These are immobile, tube-like veins of fruiting bodies that form a net. The best example of this is Hemitrichia serpula, which forms distinctive gold-yellow networks of tubes that will burst to reveal spores when they are mature. The other kind is the sporangium, which is a round case that holds a mass of spores. [5] An example of this is Hemitrichia clavata, which forms small sporangia held on a stalk that open to reveal brightly red to yellow coloured mature spores. [11] These spores will then disperse and change into the haploid ameoboflagellate stage, starting the process over again.

Practical importance

Two species of Hemitrichia offer important insights into the evolution of the myxomycetes. Hemitrichia serpula is probably one of the most well-known and recognizable slime molds due to its distinct golden yellow net-shaped appearance, which acts as the main morphological feature used to identify the species. H. serpula can be found in lowland forests of most of the major continents, including Asia, Europe, North America and South America, demonstrating their ability to disperse spores upwards of thousands of miles. [6] The species' distinct morphology and its extremely wide spread habitat allowed Hemitrichia serpula to be used to study the process of speciation and gene flow in the Myxomycetes. [6] DNA analysis of H. serpula was able to show that Myxomycetes, like most species, are subject to environmental barriers in gene flow, allowing for the development of new species or clades. [6]

Spores of the species Hemitrichia clavata spores were found to be viable and able to germinate after 75 years in storage. [9] This demonstrated the hardiness of the spores, as well as providing an explanation for their ability to survive widespread dispersal.

List of species

The genus Hemitrichia currently has 28 accepted species: [12]

Hemitrichia serpula Hemitrichia serpula 57955.jpg
Hemitrichia serpula

Related Research Articles

<span class="mw-page-title-main">Slime mold</span> Spore-forming organisms

Slime mold or slime mould is an informal name given to a polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are microscopic; those in the Myxogastria form larger plasmodial slime molds visible to the naked eye. The slime mold life cycle includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic multicellular or multinucleate fruiting bodies that may be formed through aggregation or fusion; aggregation is driven by chemical signals called acrasins. Slime molds contribute to the decomposition of dead vegetation; some are parasitic.

<span class="mw-page-title-main">Dictyostelid</span> Group of slime moulds

The dictyostelids or cellular slime molds are a group of slime molds or social amoebae.

<i>Physarum polycephalum</i> Species of slime mold, model organism

Physarum polycephalum, an acellular slime mold or myxomycete popularly known as "the blob", is a protist with diverse cellular forms and broad geographic distribution. The “acellular” moniker derives from the plasmodial stage of the life cycle: the plasmodium is a bright yellow macroscopic multinucleate coenocyte shaped in a network of interlaced tubes. This stage of the life cycle, along with its preference for damp shady habitats, likely contributed to the original mischaracterization of the organism as a fungus. P. polycephalum is used as a model organism for research into motility, cellular differentiation, chemotaxis, cellular compatibility, and the cell cycle.

<i>Fuligo septica</i> Species of slime mould

Fuligo septica is a species of slime mold, and a member of the class Myxomycetes. It is commonly known as scrambled egg slime, or flowers of tan because of its peculiar yellowish appearance. It is also known as dog vomit slime mold or Jasmine mold and is relatively common with a worldwide distribution, often being found on bark mulch in urban areas after heavy rain or excessive watering. Their spores are produced on or in aerial sporangia and are spread by wind.

<span class="mw-page-title-main">Myxogastria</span> Group of slime molds

Myxogastria/Myxogastrea or Myxomycetes (ICN) is a class of slime molds that contains 5 orders, 14 families, 62 genera, and 888 species. They are colloquially known as the plasmodial or acellular slime moulds.

<span class="mw-page-title-main">Trichiales</span> Order of slime moulds

Trichiales is an order of slime moulds in the phylum Amoebozoa. Trichiales is one of five orders in the group Myxomycetes, or the true plasmodial slime molds. It is also currently categorized under the superorder Lucisporidia with its sister group, Liceales. The order was first described by Thomas MacBride in 1922, and has retained the same name and status as a defined order in present phylogeny. In the plasmodium form, members of Trichiales lack a columella but have a well-developed capillitium for spore dispersal. The shape and details of the capillitium are used to define families within the order. Spores are brightly coloured, ranging from clear, white and yellow to pink and red-brown tones. The order currently has 4 families, 14 genera and 174 species. Recent molecular research has shown that while Trichiales probably represents a true taxonomic group, its sister group Liceales is likely paraphyletic, and it has been suggested that several genera from the Liceales should be reclassified under Trichiales instead.

<i>Ceratiomyxa</i> Genus of slime mould

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.

Fonticula is a genus of cellular slime mold which forms a fruiting body in a volcano shape. As long ago as 1979 it has been known to not have a close relationship with either the Dictyosteliida or the Acrasidae, the two well-established groups of cellular slime molds. In 1979, Fonticula was made a new genus of its own due to the unique characteristics of its fruiting body, with only one species: Fonticula alba.

<i>Enteridium lycoperdon</i> Slime mold

Enteridium lycoperdon, the false puffball, is one of the more obvious species of slime mould or Myxogastria, typically seen in its reproductive phase as a white 'swelling' on standing dead trees in the spring, or on large pieces of fallen wood. Alder is a common host.

<i>Brefeldia maxima</i> Species of slime mould

Brefeldia maxima is a species of non-parasitic plasmodial slime mold, and a member of the class Myxomycetes. It is commonly known as the tapioca slime mold because of its peculiar pure white, tapioca pudding-like appearance. A common species with a worldwide distribution, particularly in North America and Europe. It is often found on bark after heavy rain or excessive watering. Their spores are produced on or in aerial sporangia and are spread by wind, however beetles of the family Latridiidae are also reported to disperse the spores. Bonner states that soil invertebrates and rain mainly disperse spores as they are sticky and unlikely to be carried by air currents.

<i>Willkommlangea</i> Genus of slime moulds

Willkommlangea reticulata is a slime mold species from the order Physarales and the only species of the genus Willkommlangea. It is common worldwide, but rare in Europe. The tropics are possibly the main area of habitat.

<span class="mw-page-title-main">Hypothallus</span>

In true slime molds (myxogastria), lichens, and in species of the family Clavicipitaceae, the hypothallus is the layer on which the fruit body sits, lying in contact with the substrate. The word is derived from the Ancient Greek root hypó ("under") and thallós.

<i>Trichia decipiens</i> Species of slime mould

Trichia decipiens is a worldwide widespread slime mould species from the order Trichiida.

Prototrichia metallica is a slime mould species from the order Trichiida and the only species from the genus Prototrichia. It is mainly distributed on mountains.

<span class="mw-page-title-main">Plasmodiocarp</span>

A plasmodiocarp is a special form of fruit bodies of slime moulds. It is produced if the plasmodium concentrates during the fructification and pull back into the venetion of the plasmodium, from which the fruit body is created. The fruit body traces the process of the venetion, whereby the structure of its subsurface becomes plainly strand-shaped, branched, net or ring-shaped. The production of plasmodiocarps can be generic, or can be also caused by the deranged development of sporocarps or aethalia.

Barbeyella minutissima is a slime mould species of the order Echinosteliales, and the only species of the genus Barbeyella. First described in 1914 from the Jura mountains, its habitat is restricted to montane spruce and spruce-fir forests of the Northern Hemisphere, where it has been recorded from Asia, Europe, and North America. It typically colonises slimy, algae-covered logs that have lost their bark and have been partially to completely covered by liverworts. The sporangia are roughly spherical, up to 0.2 mm in diameter, and supported by a thin stalk up to 0.7 mm tall. After the spores have developed, the walls of the sporangia split open into lobes. The species is one of the smallest members of the Myxogastria and is considered rare.

<i>Stemonitis axifera</i> Species of slime mold

Stemonitis axifera is a species of slime mold. It fruits in clusters on dead wood, and has distinctive tall reddish-brown sporangia, supported on slender stalks.

<i>Elaeomyxa</i> Genus of slime moulds

Elaeomyxa is a genus of slime molds in the family Lamprodermataceae. As of May 2022, there are four known species in the genus. Species in this genus have been documented in North America, Eurasia, Africa, and Australasia.

<i>Trichia crateriformis</i> Species of slime mould

Trichia crateriformis is a slime mold species in the order Trichiida found in temperate areas throughout the world.

References

  1. 1 2 Gordh, G.; Headrick, D.H. (2001). A Dictionary of Entomology. Wallingford: CABI.
  2. 1 2 3 4 5 Rostafinski, J.T. (1873). Versuch eines systes der mycetozoen. Straussberg: Druck von Friedrich Wolff.
  3. 1 2 MacBride, T. (1922). The North American Slime Moulds (2nd ed.).
  4. 1 2 3 4 5 6 7 8 9 10 Stephenson, S.L. (2011). "From morphological to molecular: studies of Myxomycetes since the monograph of Martin and Alexopoulos". Vol. 50. Fungal Diversity. pp. 21–34.
  5. 1 2 3 4 5 6 Martin G.W. and Alexopoulis, C. (1969). The Myxomycetes. Iowa City: University of Iowa Press.
  6. 1 2 3 4 5 Heherson, N.; et al. (2017). "Speciation in progress? A phylogenetic study among populations of Hemitrichia serpula(Myxomycetes)". Vol. 12. PLoS One. pp. 1–14.
  7. 1 2 Bezzera, A.C.C.; et al. (2009). "Species of Hemitrichiain Brazil". Vol. 107. Mycotaxon.
  8. ↑ Fiore-Donno, A.; Clissmann, F.; Meyer, M.; Schnittler, M.; Cavalier-Smith, T. (2013). "Two-gene phylogeny of bright-spored myxomycetes (slime moulds, superorder lucisporidia)". PLoS.
  9. 1 2 3 Carlos Lado; Uno Eliasson (2017). Chapter 7 - Taxonomy and Systematics: Current Knowledge and Approaches on the Taxonomic Treatment of Myxomycetes, In Myxomycetes, edited by Steven L. Stephenson and Carlos Rojas. Academic Press. pp. 205–251.
  10. ↑ Olive, Lindsay (1975). The Mycetozoans. New York: Academic Press.
  11. ↑ Lizarraga, M.; et al. "SEM studies of the Myxomycetes from the Peninsula of Baja,California (Mexico), II Hemitrichia to Trichia". Vol. 36. Ann.Bot.Feenici. pp. 187–210.
  12. ↑ Lado, C. "An online nomenclature information system of Eumycetozoa". nomen.eumycetozoa.com. Madrid, Spain: Real Jardin Botanico CSIC.
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