Fly killed by fungus
A dead muscoid fly (most likely Muscidae), killed by, and exuding spores of, an Entomophthora fungus (Class: Zygomycetes, Order: Entomophthorales).
Order: Entomophthorales
Obligate insect fungal pathogens that feed within the live host until all the resources are spent, thereby killing the insect - at which time the fungus must sporulate to infect new living hosts. They produce short term infecting spores (conidia) under favourable conditions (eg. good humidity) and long term hardy resting structures such as chlamydospores when conditions are not favourable. The resting structures will produce conidia when favourable conditions return. Entomophthora muscae is a well known species of this order that attacks the common housefly.
Entomophthora muscae
Infecting spores attach themselves to the fly's cuticle, penetrate it to reach the hemocoel (this is the common method of entry for insect pathogenic fungi), and then the fungus will grow within using the fly's nutrients (favouring the abdomen). When the fly dies, 5-8 days later, the white conidia will begin to disperse from between the abdominal segments within 3 hours and continue to do so for the next 10-21 hours.
Odd Behaviours and Lures
This fungus has fascinated me, especially for the way it is reported to hijack host behaviour and to set lures for potential hosts - both very successfully serving it's own greater good.
You'll notice in the photo above that the fly has died in a peculiar position. Infected flies will die in high positions, on the underside of overhanging objects, and with wings and legs outstretched - such positioning just prior to death is also observed for many other insects lethally infected with similar fungi. It is thought that this odd host behaviour rewiring by the pathogen increases successful spore dispersion and infection, especially of aerial insects.
Another trick Entomophthora muscae play to ensure greater spread through host populations is to make the dead female highly attractive to males. It has not yet been determined how the fungus achieves this but male flies who happen upon a sporulating female cadaver have no power to resist it and will immediately engage in "extensive courtship". Hence, potentially becoming infected themselves or even carrying infecting spores to another mate.
The Co-evolutionary Battle Heats Up
Flies invaded with Entomophthora fungi have clearly demonstrated 'behavioural fever' whereby they deliberately seek, and bask, in heats above 40 degrees Celsius in the first days of infection. The high raising of body temperatures acts to suppress the pathogen. The obvious benefits of fever are an increase in the onset time of the disease giving the fly a greater chance to complete it's lifecycle and thus pass on this beneficial trait. Fever therapy has also been observed in infected grasshoppers and caterpillars resulting in reduced mortality rates. So should you find your pet house fly 'liaising' with an infected dead fly, a program of sauna therapy is highly recommended.
References:
Interactions between fungal pathogens and insect hosts. AE Hajek & RJS Leger. Annual Review of Entomology, 1999, vol. 39, pp. 293-322.
Effect of the entomophathogenic fungus, Entomophthora muscae (Zygomycetes: Entomophthoraceae), on sex pheromone and other cuticular hydrocarbons of the house fly, Musca domestica. L Zurek, DD Watson, SB Krasnoff & C Schal. Journal of Invertebrate Pathology, 2002, vol.80, pp. 171-176.
Bizarre interactions and endgames: entomopathogenic fungi and their arthropod hosts. HE Roy, DC Steinkraus, J Eilenberg, AE Hajek & JK Pell. Annual Review of Entomology, 2006, vol. 51, pp. 331-357.
Fly killed by fungus
A dead muscoid fly (most likely Muscidae), killed by, and exuding spores of, an Entomophthora fungus (Class: Zygomycetes, Order: Entomophthorales).
Order: Entomophthorales
Obligate insect fungal pathogens that feed within the live host until all the resources are spent, thereby killing the insect - at which time the fungus must sporulate to infect new living hosts. They produce short term infecting spores (conidia) under favourable conditions (eg. good humidity) and long term hardy resting structures such as chlamydospores when conditions are not favourable. The resting structures will produce conidia when favourable conditions return. Entomophthora muscae is a well known species of this order that attacks the common housefly.
Entomophthora muscae
Infecting spores attach themselves to the fly's cuticle, penetrate it to reach the hemocoel (this is the common method of entry for insect pathogenic fungi), and then the fungus will grow within using the fly's nutrients (favouring the abdomen). When the fly dies, 5-8 days later, the white conidia will begin to disperse from between the abdominal segments within 3 hours and continue to do so for the next 10-21 hours.
Odd Behaviours and Lures
This fungus has fascinated me, especially for the way it is reported to hijack host behaviour and to set lures for potential hosts - both very successfully serving it's own greater good.
You'll notice in the photo above that the fly has died in a peculiar position. Infected flies will die in high positions, on the underside of overhanging objects, and with wings and legs outstretched - such positioning just prior to death is also observed for many other insects lethally infected with similar fungi. It is thought that this odd host behaviour rewiring by the pathogen increases successful spore dispersion and infection, especially of aerial insects.
Another trick Entomophthora muscae play to ensure greater spread through host populations is to make the dead female highly attractive to males. It has not yet been determined how the fungus achieves this but male flies who happen upon a sporulating female cadaver have no power to resist it and will immediately engage in "extensive courtship". Hence, potentially becoming infected themselves or even carrying infecting spores to another mate.
The Co-evolutionary Battle Heats Up
Flies invaded with Entomophthora fungi have clearly demonstrated 'behavioural fever' whereby they deliberately seek, and bask, in heats above 40 degrees Celsius in the first days of infection. The high raising of body temperatures acts to suppress the pathogen. The obvious benefits of fever are an increase in the onset time of the disease giving the fly a greater chance to complete it's lifecycle and thus pass on this beneficial trait. Fever therapy has also been observed in infected grasshoppers and caterpillars resulting in reduced mortality rates. So should you find your pet house fly 'liaising' with an infected dead fly, a program of sauna therapy is highly recommended.
References:
Interactions between fungal pathogens and insect hosts. AE Hajek & RJS Leger. Annual Review of Entomology, 1999, vol. 39, pp. 293-322.
Effect of the entomophathogenic fungus, Entomophthora muscae (Zygomycetes: Entomophthoraceae), on sex pheromone and other cuticular hydrocarbons of the house fly, Musca domestica. L Zurek, DD Watson, SB Krasnoff & C Schal. Journal of Invertebrate Pathology, 2002, vol.80, pp. 171-176.
Bizarre interactions and endgames: entomopathogenic fungi and their arthropod hosts. HE Roy, DC Steinkraus, J Eilenberg, AE Hajek & JK Pell. Annual Review of Entomology, 2006, vol. 51, pp. 331-357.