''Meristacrum'' is a fungal
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
in the monotypic
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Meristacraceae, of the order
Entomophthorales
The Entomophthorales are an order of fungi that were previously classified in the class Zygomycetes. A new subdivision, Entomophthoromycotina, has recently been circumscribed for them.
Most species of the Entomophthorales are pathogens of ins ...
.
They are parasites of soil invertebrates, they typically infect
nematodes,
and
tardigrades.
[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 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 unicellu ...
conditions.[
]
History
The family Meristacraceae was specifically erected to hold the genus ''Meristacrum'' in 1940.[
The genus ''Meristacrum'' gets its name from the Greek word ''meristos'' which means 'divided'.][
Three genera that were formerly included in Ancylistaceae 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 bearing several conidia
A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to t ...
.
Genera ''Ballocephala'' and ''Zygnemomyces'' were later then transferred to subdivision Kickxellomycotina, 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 (skin) of a live nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...
, 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 are often formed within the host, and the primary conidia also have the ability to produce typically smaller secondary conidia.[
]
Description
They have vegetative growth which is mycelial
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates in ...
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
An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or ...
(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
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
and interphase
Interphase is the portion of the cell cycle that is not accompanied by visible changes under the microscope, and includes the G1, S and G2 phases. During interphase, the cell grows (G1), replicates its DNA (S) and prepares for mitosis (G2). A c ...
, the nucleolus is prominent,[ and central.]
The resting spores ( zygospores) 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 (scientific names) in the fungus kingdom. the project is based at the Royal Botanic Gardens, Kew, one of three partners along with Landcare Research and the Institute of Mi ...
;
* ''Meristacrum asterospermum
''Meristacrum'' is a fungal genus in the monotypic family Meristacraceae, of the order Entomophthorales.
They are parasites of soil invertebrates, they typically infect nematodes, and tardigrades.P. F. Cannon and P. M. Kirk (Editors) David J. Mc ...
''
* ''Meristacrum milkoi
''Meristacrum'' is a fungal genus in the monotypic family (biology), family Meristacraceae, of the order Entomophthorales.
They are parasites of soil invertebrates, they typically infect nematodes, and tardigrades.P. F. Cannon and P. M. Kirk (Ed ...
'' (syn. ''Tabanomyces milkoi'' )
Former species; ''M. pendulatum'' is now '' Zygnemomyces pendulatus'', Mucoromycota
Mucoromycota is a division within the kingdom fungi.
They include a diverse group of various molds, including the common bread molds ''Mucor'' and ''Rhizopus''. It is a sister phylum to Dikarya. It consists of mainly mycorrhizal fungi, root end ...
Distribution
Meristacraceae species have been found in the Amazon rainforest, Brazil.
References
{{Taxonbar, from1=Q4290939, from2=Q10581854
Entomophthorales
Zygomycota genera