Entomophthora

''Entomophthora'' is a fungal genus in the family Entomophthoraceae. Species in this genus are parasitic on flies and other two-winged insects. The genus was circumscribed by German physician Johann Baptist Georg Wolfgang Fresenius (1808-1866) in 1856.Fresenius, G. 1856. Botanische Zeitung 14, 882-883.

This fungus is parasitic and undergoes a number of stages within its life cycle, these include; infection, incubation, sporulation and mummification. Within each stage, this pathogen invades the host’s body cells, utilising the insect’s nutrients allowing it to take control over the brain just before the host’s death.

Entomophthora reproduces asexually through both budding and spores. When in the host’s body, the pathogen utilises budding as a form of growth. This is done through a fungi cell developing a bud (daughter cell) on the parent cell. The parent cell then replicates its DNA and provides the daughter cell with this DNA. The daughter cell is then able to detach itself from the parent cell resulting in multiplication of the fungus. Spores are another mechanism that is utilised as a method of reproduction; the spores act like seeds in that they will flourish when environmental conditions are appropriate and begin to grow hyphae – root like filaments. These hyphae then develop into the body of the fungus where the spores can be created once again and released into the environment to ensure further reproduction occurs again.

Similarly, spores are utilised as a method of transmission of this parasitic disease, when spores come in contact with the insect either through consumption or direct contact, the pathogen is able to infect the insect resulting in the beginning on the life cycle. The insect however has immune responses that fight against these parasites in order to defend themselves from infection. Hemocytes are the cells within the immune response that are able to detect the entry of a pathogen and initiate the immune response to kill the foreign particles within the insect.

Physical characteristics

Description

Entomophthora is a type of fungal pathogen that is parasitic towards flies and other two-winged insects. When entered into a host’s body, the fungal pathogen begins to invade the body cells and take control of the hosts which, in turn results in death. This relationship between a host and an organism is called parasitism. the parasite lives off or within another organism, in this case the fly (host) and causes harm or even death to the host. Entomophthora outbreaks commonly occur in temperate regions often during spring and autumn. Spores are the cause infection of a host, this usually occurs in cool and humid conditions commonly in areas where flies rest.

Life cycle

Infection occurs when an insect comes in contact with the Entomophthora pathogen. Once the insect has been infected, the fungal disease begins its transmission and development throughout the body, causing harm and soon death to the host. The stages in which this pathogen undergoes to impact the host and cause harm, is referred to its life cycle.

The first stage of the life cycle is infection, referring to the invasion of micro-organisms into a genome, these micro-organisms are foreign to the body. Within this stage, the host come in contact with a conidia – a type of reproductive spore through touch or ingestion. When the conidia is within the host’s body, it beings to germinate. Germination refers to the process in which an organism grows from a spore. Here, the conidia present within the body begins to produce hyphae, these act like the roots of the fungi as they grow and branch out within the body of the host. Ultimately initiating the spread of the pathogen throughout the insect.

The next stage of the pathogen’s life cycle is incubation; this is the period of time between the insect's first exposure to the pathogen and the occurrence of the first symptom. Within this period the internal hyphae combine digestive enzymes and utilise pressure to penetrate through a number of cuticle layers of the host. This allows for the spread of the pathogen throughout the whole body of the host, infecting the insects blood and tissue. The fungal cells are able to absorb water and nutrients from the hosts body ensuring the pathogen’s survival.

This initiates the third stage of the life cycle; sporulation. Within this stage, the fungal pathogen begins to reproduce, this is done through the formation of spores from vegetative cells and budding. These spores are then released within the insect and infect the membrane areas within the host’s abdominal cuticle. The disturbance of blood flow, tissue and abdominal cuticle causes the pathogen to enter its last stage of its life cycle. In the host, the appearance of this stage is apparent due to abdominal swelling creating a striped pattern that remains even after death.

The last stage of the Entomophthora life cycle is mummification of the cadaver, in which this stage causes death to the host. The pathogen has interrupted and overtaken the host’s main vital mechanisms for survival, so the host’s body is no longer able to function normally and defend itself against the pathogen or any other threats. The mycelium – a group of hyphae- is then able to grow within the brain, controlling the behavioural aspects of the fly. The infection of the fly’s brain allows the pathogen to gain control over the fly’s movements. The pathogen commonly forces the host to locate itself on a high point of a surface, straighten out its back legs and open its wings. This allows for the hyphae to maximise growth within the body of the host causing death. Once death has occurred, the pathogen then releases its spores out into the environment to allow for transmission and reproduction once again. The position in which the fly remains ensures that the release of spores is dispersed as widely as possible to ensure transmission to another insect.

Reproduction

Reproduction refers to the process in which an offspring is formed via asexual reproduction or sexual reproduction. Asexual reproduction involves one parent, producing a genetically identical offspring, to the parent cell. Whereas sexual reproduction involves the meeting and fertilisation of gamete cells in order to produce a genetically different offspring. Fungi type organisms reproduce asexually through the release of diploid spores. Spores are micro unicellular cells that are released and dispersed into the environment in a mass of numbers to increase the likelihood of further development and growth of the fungus. As spores are very small in size, they are easily moved via environmental conditions, that being wind, water, or even on an animal’s fur. These spores will find favourable conditions and successfully flourish, develop and grow into the structure and body of the fungi.

Development of the fungus via spores is initiated through germination; this marks the beginning of fungal development. Spores will begin to develop filaments called hyphae; these are root like structures of the fungi as they branch out into the environment absorbing any available water and other nutrients required for survival. Groups of hyphae will interconnect, forming the main fungal body, the mycelium. The fungi will soon develop a sporangiophore