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Monday, November 17, 2008

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Predictive Biology

Like many biologists I imagine, I was delighted with this story, about a species of ant in which a few ants, each night, make it their business to seal the nest from the outside. This means that the colony is safer but the ants left outside die.

While biology is not particle physics, with the existence of new particles predicted by theory, it should be possible to predict biological phenomena to some extent at least. Knowing that worker ants and other social insect workers are altruistic (bees dying when they sting; termites that literally explode to protect the colony), it would not have been hard to predict the existence of ants that sacrifice themselves by sealing the nest from the outside. A few minutes thought would have done it.

Similarly, lazy ants and male stuffing in wasps could have been predicted from first principles.

I am aware of at least one prediction from first biological principles, by the McMenamins, as part of their "hypersea" hypothesis:

' Yet another test would be to look for organisms that exploit Hypersea in ways allowed by the hypothesis but that are thus far unidentified. For example, just as marine animals have become terrestrial parasites, photosynthesizing algae or bacteria should also find an animal to be a fine aquatic habitat. Mark suggests that there are (or once were) terrestrial counterparts of the Ediacaran fauna, animals that survive by hosting photosynthesis. "Whenever I give a lecture on Hypersea," says Mark, "someone comes up to me and says, 'I think there's one out there, too, and I'm going to find it.'" Mark himself will hunt for fossils of such life-forms. "I want to go into the Appalachian Mountains and look for evidence of unusual hypermarine linkages in these kinds of organisms. Maybe my photosynthetic land animal is there." '

Not quite what McMenamin had in mind, but pretty close, is the case of the South American sloth, which has symbiotic photosynthetic bacteria in its fur:

http://en.wikipedia.org/wiki/Sloth

" In moist conditions, the fur hosts two species of symbiotic cyanobacteria, which provide camouflage[3][4]. The bacteria provide nutrients to the sloth when licked during grooming.[citation needed] Sloth fur is also host to algae; this algae colors the coat green and acts as camouflage.[3] Because of this algae, sloth fur is a small ecosystem of its own, hosting many species of non-parasitic insects.[5]. "

It seems likely that to be a terrestrial animal hosting photosynthetic symbionts one would have to stay still and spend a lot of time in the sun. The sloth's arboreal life and slothful ways would probably meet this requirement.

Some time ago, as I wrote here on this blog, I made a theoretical prediction which turned out to be true in one instance at least. Here is what I wrote:

Plants as Doctors?

For some time, I have toyed with the idea that plants might provide substances of medical value to animals that perform useful services for them. For example, do fruiting plants provide medically useful chemicals to monkeys that eat their fruit and help spread their seeds? Could plants provide some curative products to animals that eat their foliage? That is, could a plant's leaves or fruit provide chemicals designed to help prevent or cure animals' diseases?

Certainly plants frequently secrete materials that are intended to stop animals from feeding on them; but could they do the opposite and encourage the health and survival of animals that render them services - such as spreading their seeds or fertilising them with their droppings - by providing them with useful medications? Is it possible that some of the useful drugs that are derived from plants have their origin in keeping wild animals healthy - for the mutual benefit of the plants and animals? Is this one reason why fruit seems to be so valuable in the human diet?

There is one case that appears to show "proof-of-concept". For an account see "New Scientist" (UK) - the issue of 30 May 1998, p.27. The note is short so I'll quote it in full:

" A Beautiful Way to Keep Bees Healthy

This flower [illustrated], which is native to South and Central America, lavishes an unexpected gift on the wild trigona bees that pollinate it - a coat of resin spiked with powerful antibiotics that probably help keep their nests free of harmful bacteria. John Loquvam of the University of Alaska in Fairbanks exposed bacteria known to infest the hives of honey bees to the resin of the flower, *Clusia grandiflora*. The resin was almost as effective at killing the bacteria as conventional antibiotics. 'It's the first time this has been shown in any plant as a pollinator reward', says Loquvam. Resin from the female plants was far more potent than extracts from male plants. Loquvam suspects the females are compensating for the fact that males produce 15 times as many flowers. "

It seems likely that this principle - of plants providing useful animals with medicinal rewards - will be found to apply in other cases as well. It would certainly be in the interests of plants to ensure that useful animals remain free from illness and able to continue to serve the plants' purposes.


Julian


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