Sunday, 31 May 2020

Unintelligent Design - Spittlebugs and Bacteria

Spittlebug, the nymph stage of the froghopper, Clastoptera proteus
Two bacteria allow spittlebugs to thrive on low-nutrient meals | Krishna Ramanujan, Cornell Chronicle

Imagine you're an omniscient, omnipotent designer of living organisms and you've designed an insect you want to live and thrive. How do you go about providing it with food?

Well, you design it to live on the low-nutrient sap obtained from the xylem of plants, then you provide it with a ludicrously complex system of symbiotic bacteria which take this poor food supply and turn it into the essential chemicals the insect needs to live on, apparently.

Of course, you need to design special structures for these bacteria to live in. For some reason, you forgot all about the metabolic processes you designed for millions of creations, so you designed this unique one afresh, like re-inventing a wheel.

This exquisite example of the lack of intelligence in natural 'design' was discovered in the spittlebug, Clastoptera proteus, by Cornell University researchers led by Nana Ankrah. Their findings were published in the journal of the International Society for Microbial Ecology recently.

Spittlebugs are the nymph stages of the froghopper which produces what we called 'cuckoo spit', because it appears at about the same time as cuckoos return from their winter migration. As a youngster in Oxfordshire, I once walked through the long grass of a hay meadow that has so much 'cuckoo spit' that the legs of my trousers were soon as wet as if I had walked through a river.

Krishna Ramanujan, writing in The Cornell Chronicle explains:

Spittlebugs get their name from the bubbly spit they create in plant branches. The clusters of spit keeps them from drying out and allow them to hide from predators. There they feed on xylem plant sap, a very low-value food; xylem transports water and minerals from the plant’s roots to its leaves.

“No animal should be able to subsist on xylem alone – it’s really just water and a few nutrients,” said lead author Nana Ankrah, a postdoctoral researcher in the lab of Angela Douglas, the Daljit S. and Elaine Sarkaria Professor of Insect Physiology and Toxicology in the Department of Entomology in the College of Agriculture and Life Sciences.

The answers to how these bugs survive lie in two types of bacteria that live in separate spittlebug organs, called bacteriomes; one is red, the other orange. Other similar insects that feed on plant sap have just one bacterial partner to help produce high-quality amino acids, the building blocks of proteins.

“We wanted to understand if there were any advantages to having two bacterial symbionts on this very poor diet,” Ankrah said.

The researchers collected local spittlebugs, removed their red and orange bacteriomes, incubated the bacteria separately in glucose, and ran metabolic experiments and computer model simulations.

They discovered that the red bacteriome uses a process known as aerobic glycolysis to process glucose, from which the bacteria synthesize seven essential amino acids. Two byproducts of this process, pyruvate and lactate, are assimilated by the orange bacteriome to create ATP molecules, which make energy for cells. The energy boost from ATP allows the bacteria in the orange bacteriome to produce three additional essential amino acids that require a great deal of energy to produce.

Having two bacterial partners instead of one works because they have this method for exchanging products from one bacterium to the other to increase the overall energy available to them, Ankrah said.


As I said in my book, "The Unintelligent Designer: Refuting the Intelligent Design Hoax", the hallmarks of good, intelligent design is minimal complexity and maximal simplicity. In this example of the spittlebug, we have an example of a massively complex system involving two symbiotic species needing to pass products back and forth to achieve what millions of other species achieve more simply, given a diet with the right nutrients. As good an example of unintelligent design as you could wish to find, but an example of what an undirected, utilitarian, process can produce over millions of years, where whatever is better at providing descendants than the previous is kept, and the old discarded.

Incidentally, this system is similar in principle to that found in cancers where some cells produce pyruvate and lactate by aerobic glycolysis which are then consumed by other specialised cells to create energy. Presumably, creationism's intelligent [sic] designer is supposedly responsible for both.







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