sarahkeenihan

And speaking of poo…

In November 2013 on November 30, 2013 at 8:48 pm

Kirsti honeydew Ultracoelostoma Noble text

Kirsti: Earlier this week, Mia wrote about POO POWER! I too have a story about the science of poo.

Lots of insects feed on phloem, a.k.a. plant sap. And just as we excrete waste from an omnivorous diet as a conglomerative breakdown of those foods, sap-sucking creatures such as scale insects, aphids, psyllids and others  poo honeydew, the waste from the sugar-rich foods they ingest.

Even further down the food chain exist microbial communities that survive on the honeydew (poo) that makes its way down onto the surface of leaves, which are little ecosystems in their own right. If you live there, you live in the phyllosphere!

We don’t know that much about life in the phyllosphere. But recently some scientists in New Zealand looked at fungi from the phyllosphere of native beech forests in New Zealand. Endemic scale insects that live on these trees produce up to 4500 kg  dry weight/ha/year of honeydew.

The insects use an ingenious method to keep themselves clean and minimise fungal growth on their bodies:  the honeydew is flicked off the end of an anal wax-tube (as shown in picture).

Together, all the excreted sugary delights from these creatures  fuel the growth of an abundant mould. The mould appears black and kind of powdery from afar, with human eyes. But look closer – a LOT closer, down a scanning electron microscope then even closer at their genes – and you will see a circus of species, a kaleidoscope of colour, most of which cannot be identified!

The study that identified these fungi communities in New Zealand emphasises that despite the sooty mould being such a ubiquitous element in the scale insect-beech system, we know very little about the microbial diversity. The conference I have just been at highlighted the same gap in knowledge for ecology in general.

So people, let your imaginations run wild! Poo of all sorts of species powers communities, even if it’s a microscopic one in the phyllosphere.

Oh, if you’re interested in microbial communities supported by your own body, I’d highly recommend reading The Wild Life of Our Bodies by Rob Dunn, a fantabulous science writer from North Carolina State University.

[image thanks to David Noble]

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