Yellow dung fly fungal parasites wanted!

[RobK]

Hello everyone

Just a note to say that we have a research project at Queen Mary, University of London and the Institute of Zoology on behavioural modification by parasites, and I'm hoping that someone might be able to help us get hold of some parasitic fungus. The fungus in question infects yellow dung flies (Scathophaga stercoraria) and is called Entomophthora scathophagae. The flies are the big yellow flies that you get on cow or sheep dung, and when they are killed by the fungus they are usually found in a very characteristic pose with their wings outspread on vegetation or fences, usually on the underside of leaves if on vegetation. You can sometimes see the fungal spores growing out of the joints on the exoskeleton on the abdomen. If anyone is out and sees any flies that are infected I'd be really grateful if you could drop me a line: r.knell@qmul.ac.uk

Thanks for any help!

Rob

[DivingDave1980]

Hi Rob,

I will certainly keep an eye out for any that I see, although I can't promise anything. Would you also like photographs / samples if available? Or do you just want a location so you can come and have a look yourself. I have to say although I've seen many Scathophaga stercoraria in my time, I can't recall seeing dead ones infected by fungus - but I suppose I've never looked before!!

Can you give us some more information about the fungus / fly life cycle? I would certainly be very interested, and I'm sure many others on here would be too!

Dave.

[nutmeg]

I'll keep my eyes open. Quite often see various flies that have been infected with Entomophthora sp., although can't recall any having been Yellow dung flies. Would be good to see.

[RobK]

Thanks for the interest folks. If they're anywhere within about two and a half hours of London then just a location would be fine, if further afield then let me know and I might ask you to collect some for me depending on where exactly they are.

More information about the fungus: it's a parasite that's transmitted directly from fly to fly by its sticky conidia (spores). It infects the fly, grows through its body and then kills it. Once it's dead the fungus releases infectious conidia from the cadaver and if these get stuck to a new host the process starts again. There are probably spring and autumn epidemics in the dungfly population, and we'd like to get some samples from the spring one. It's very closely related to Entomophthora muscae, which kills houseflies and you might well have seen flies killed by this latter fungus. We're interested in it because it's reported to manipulate the behaviour of the host before death - this is a description of it from a grant proposal.

Scathophaga stercoraria is frequently infected with the entomopathogenic fungal parasite Entomophthora scatophagae (Maitland, 1994; Steenberg et al., 2001). During the autumn, infection rates in the region of 50% have been reported from Denmark (Steenberg et al., 2001), and anecdotal reports from the UK suggest that similar prevalence can occur here. The fungus kills the host and then releases infectious conidia from the cadaver, and it appears to change the perching behaviour of infected flies in a number of ways just before they die (Maitland, 1994). Cadavers are found higher on vegetation, on the side away from the prevailing wind, and on the underside of leaves, whereas healthy flies perch further down in the vegetation, on the tops of leaves and at random with respect to the prevailing wind. Maitland suggested that all of these changes in perching behaviour will lead to an increased transmission rate for the fungus: the wind will blow the sticky conidia away from the plant stem and onto the healthy flies perching below, and the position under the leaf means that the cadaver will be protected from rain, and that the spores will not simply stick to the leaf that the fly perched on before death.

Thanks for any help with this.

Cheers

Rob