Meristacrum
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''Meristacrum'' is a fungal
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
in the monotypic
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Meristacraceae, of the order
Entomophthorales The Entomophthorales are an order of fungi that were previously classified in the class Zygomycetes. A new subdivision, Entomophthoromycotina, in 2007, was circumscribed for them. Most species of the entomophthorales are pathogens of insects ...
. They are parasites of soil invertebrates, they typically infect
nematodes The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (he ...
, and
tardigrades Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged Segmentation (biology), segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who calle ...
.P. F. Cannon and P. M. Kirk (Editors) David J. McLaughlin and Joseph W. Spatafora (Editors) Fungi strains such as ''Meristacrum asterospermum'' and '' Zygnemomyces echinulatus'' have been identified as potential sources of
biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...
against parasitic nematodes. Although, they have yet to be raised within laboratory or
Axenic In biology, axenic (, ) describes the state of a culture in which only a single species, variety, or strain of organism is present and entirely free of all other contaminating organisms. The earliest axenic cultures were of bacteria or unicellul ...
conditions.


History

The family Meristacraceae was specifically erected to hold the genus ''Meristacrum'' in 1940. The genus ''Meristacrum'' gets its name from the
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
word ''meristos'' which means 'divided'. Three genera that were formerly included in
Ancylistaceae The ''Ancylistaceae'' are a family (biology), family of fungi in the order Entomophthorales. The family currently contains the genera: ''Ancylistes (fungus), Ancylistes'', ''Macrobiotophthora'', ''Conidiobolus''. ''Capillidium'' was added in 2020 ...
family; '' Ballocephala'', ''Meristacrum'', and '' Zygnemomyces'', were transferred to Meristacraceae by American mycologist Richard A. Humber in 1989, because these fungi all produce a simple, upright
conidiophore A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...
bearing several
conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...
. Genera ''Ballocephala'' and ''Zygnemomyces'' were later then transferred to subdivision
Kickxellomycotina Kickxellomycotina is a fungus grouping in the subkingdom of Zoopagomyceta . The name was changed from "Harpellomycotina", because "Kickxellomycotina" had an older stem. It came from the genus '' Kickxella'', named after Jean Kickx. Orders inc ...
, based on the bifurcate, plugged septa in their vegetative hyphae, this was also confirmed by Humber (in 2012).


Life cycle

In general, the various fungal species of Meristacraceae, find a host using a germ hyphae produced by adhesive spores that were actively (ballistically) discharged and airborne.Carl A. Batt and Pradip Patel (Editors) They use conidial propulsion, or by 'papillar eversion', which is by fluid discharge by a swollen subtending cell, or passively released from a short pedicel. Conidia then adhere to the
integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, Exoskeleton, shell, germ or Peel (fruit), rind. Etymology The term is derived from ''integumentum'', which is Latin for "a coverin ...
(skin) of a live
nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...
, then either penetrate directly by a germ tube or germinate externally and produce secondary conidia. Resting spores germinate and produce a single erect conidiophore similar to those produced by thallodic segments The fungus then invades the abdomen of the host and a systemic infection develops. Once the host has died, sporophores are produced, typically between the individual segments of the abdomen, where a new generation of actively discharged spores are produced.
Resting spores A resting spore is a resistant cell, adapted to survive adverse environmental conditions. Resting spore is a term commonly applied to both diatoms and fungi. In fungi and oomycetes A resting spore can be a spore created by fungi which is thickly ...
are often formed within the host, and the primary conidia also have the ability to produce typically smaller secondary conidia.Frank Matthews Dugan


Description

They have vegetative growth which is
mycelial Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fou ...
at first, then forming hyphal bodies. These are usually spherical to rounded. The Sporophores (conidiophores) are simple, unbranched,D.H. Howard (Editor) solitary cylindrical or slightly clavate, bearing terminal conidiogenous cells. The spores (conidia) are terminal, spherical, single celled, unitunicate (single walled), and forcibly by papillar eversion or passively discharged. The secondary spores are present or absent, either similar to primary spores and are also forcibly discharged or passively discharged from strongly narrowed and elongate sporophores. The nucleus is small, (about 3-5 μm (micron, or micrometre)) not clearly visible during
mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...
and
interphase Interphase is the active portion of the cell cycle that includes the G1, S, and G2 phases, where the cell grows, replicates its DNA, and prepares for mitosis, respectively. Interphase was formerly called the "resting phase," but the cell i ...
, the nucleolus is prominent, and central. The resting spores (
zygospores A zygospore is a diploid reproductive stage in the life cycle of many fungi and protists. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are formed in zygosporangia after the fusion of specialized budding stru ...
) are formed by hyphal conjugation (conjugation of neighbouring hyphal cells or scalariform conjugations between adjacent hyphae), the zygosporangium (episore) is hyaline (glass-like or transparent) or slightly pigmented and smooth or ornamented. The zygospore (endospore) is ovoid and smooth or globose to sub-globose and roughened, germinating directly to produce secondary spores or a sporophore.


Species

As accepted by
Species Fungorum ''Index Fungorum'' is an international project to index all formal names (Binomial nomenclature, scientific names) in the fungus Kingdom (biology), kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partn ...
; * '' Meristacrum asterospermum'' * '' Meristacrum milkoi'' (syn. ''Tabanomyces milkoi'' ) Former species; ''M. pendulatum'' is now '' Zygnemomyces pendulatus'',
Mucoromycota Mucoromycotina is a subphylum of uncertain placement in Fungi. It was considered part of the phylum Zygomycota, but recent phylogenetic studies have shown that it was polyphyletic and thus split into several groups, it is now thought to be a para ...


References

{{Taxonbar, from1=Q4290939, from2=Q10581854 Entomophthorales Zygomycota genera