Sunday, June 29, 2008

Saturday, June 14, 2008

Fungal Entomophagy vs Insect Mycetophagy: a lesson from Butch

Here's a link to a flash game featuring an insect-eating mushroom named Butch, as opposed to an insect eating mushrooms. The war of the creepy crawlies goes both ways, with lots of insect groups reliant on fungi for food and shelter, and fungal taxa reliant upon insects. I work with ophiostomatoid fungi, which includes things like the causal agents of Dutch elm disease, Ophiostoma ulmi and O. novo-ulmi. These fungi rely upon their insect vectors for transportation, and have sticky spores on long appendages to "paint" their beetles with spores as they leave the tree they were born and raised in to move on to their next victim. Ambrosia beetles possess mycangia, which are pockets on their exoskeletons, specifically for carrying the spores of their fungi, which are what the larvae eat. Some mycangia even have glands to feed the fungi while in transit!
There are other mycetophagous families of beetles, such as the pleasing fungus beetles (Erotylidae), hairy fungus beetles (Mycetophagidae), handsome fungus beetles (Endomychidae), tooth necked fungus beetles (Derodontidae), silken fungus beetles (Cryptophagidae), round fungus beetles (Leioidae). The list goes on and on. What do you expect? They're BEETLES.
Anyone who has hunted for wild edible mushrooms knows how much little creepy crawlies are also enamored of tasty basidiocarps. Springtails, fungus gnats, and other arthropods are often the first on the scene, and can protein-enhance an unwary mycotroph.
One of the best seminars I've ever witnessed was about leaf-cutting ants in the tropics. Leaf cutters don't eat the leaves, they feed them to their fungus gardens underground in vast colonies. It turns out that the fungus they eat is susceptible to a mycoparasite, which is inedible to the ants. How do the ants tend there gardens? The first thing they do is to try and weed their garden physically. When that doesn't work, they use another symbiont, a bacterium that produces and antibiotic, to treat the infestation.

As for insect-eating mushrooms, there's nothing quite like Butch out there, but there are some pretty neat entomoparasites, like the zygomycetous Entomophthorales. When Entomophthora muscae infects a fly, it will hijack its nervous system, making it crawl upwards until it explodes, thus serving as a great vector for the wind-blown spores.
Beauveria bassiana (Hyphomycetes) will attack just about anything with an exoskeleton, I am told, and is being studied as a potential biological control agent for many insect pests.
And there's also the nematode killing fungi, which can catch the tiny worms in loops of hyphae, or inject spores into their prey, or release swimming spores after their quarry, or just stick them on their bodies. But nematodes are not insects, of course, so let's not get too excited.