Friday, September 4, 2015

An Aphid, an Ash and a Mushroom

Mark Bower found this unusual mushroom in the woods above Bull Creek.  It is unusual in that its stem isn't centered in the cap but more off to the side.  He identified it as Boletinellus merulioides, a bolete fungus that is found around ash trees this time of year.  Most mushrooms associated with particular trees are mycorrhizal, living in symbiosis with tree roots.  They absorb minerals from the soil and exchange them with the tree for nutrition the tree produces by photosynthesis.  Not so with B. meruliodes, which makes its living off of aphids!

Meliarhizophagus fraxinifolii, the "leafcurl ash aphid" creates a curl in emerging ash leaves and lives there while parasitizing energy from the tree.  Like many other aphids, the ash aphid produces honeydew but it also secretes a protective wax that keeps it from accumulating on its body.  The B. meruliodes fungus mycelium forms hollow sclerotium that surround the aphids in a protective layer.  In exchange it absorbs the aphid's honeydew as its sole source of nutrition.

Leafcurl Ash Aphid - Whitney Cranshaw, Colorado State University
Whitney Cranshaw, Colorado State University, - See more at:
Whitney Cranshaw, Colorado State University
Whitney Cranshaw, Colorado State University
Honeydew is produced by aphids, some scale insects and even the caterpillars of Lycaenidae butterflies.  Some species of ants farm aphids, protecting them from harm in exchange for their honeydew.  An article in Wikipedia explains, "When their (aphids') mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening," an icky fact that doesn't seem to bother the fungus.  That gives new meaning to the saying "no guts, no glory."

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