Two Tall Tales
All of this was explained with pencil sketches, a few indecipherable words in Swedish thrown in, and a lot of enthusiasm. I was immediately suspicious. It sounded like science fiction to me. How could the amoebas find each other? Weren't they microscopic? How could a bunch of separate little animals get together and make a large one? It sounded too much like the story about catching boneless flounders my brother had told me. I rolled my eyes and offered him my leg, saying, "Go ahead, pull the other one." My Mom, who was listening, said, "Daddy, you have cried wolf too often." I had no clue what she meant, but continued to be resistant to his biology lecture until he finally gave up.
Then, in my freshman biology class, I discovered that Daddy Pop had told me the unvarnished truth. Slime molds really do as he described, and they have been the subjects of intense study because of their unique life history. They locate each other by detecting the chemicals they each emit, sort of like ants do. They are able to transform from separate cells into a multicellular organism that has clearly defined parts: base, stalk, and sporangia. Understanding how they manage this may allow biologists to more clearly understand the origin of multicellular life, and how cancers form. They are important parts of forest ecosystems, because they help recycle organic material.
Last fall one of my colleagues at the college where I teach collected several slime molds, already in the spore producing stage, and I was able to take them home. I climbed the slope behind the house and was carefully depositing bits of orange stuff here and there when one of the neighbors asked what I was doing. I replied, "Scattering slime mold spores." He nodded politely and walked away, fast, dragging his little dog with him. I hope some of those spores germinated into tiny amoebas, but I will not know until November or December, when I hope to see orange slimy blobs on my bark mulch. If I do see any, I'll warn my neighbors not to disturb them, for they are busy recycling.
2. Acacias, Ants and Trees of Death
My parents and older siblings lived five years in Venezuela during the 1940's. Papa worked for Gulf Oil, participating in the American rape and destruction of rain forest and the exploitation of Venezuelan natural resources. Of course, he didn't know he was doing that. He thought he was just lucky to have a great job. I was born there, in a tiny hospital built for American workers.
Papa spoke pretty good Spanish, from growing up in the Texas Rio Grande valley and playing with Mexican kids. When we were in Venezuela, he befriended the local people and housed his family outside the company compound, which was an enclave for Americans who did not want to rub shoulders with the locals, or learn their language. From his native friends, Papa heard all kinds of interesting stories and folk tales, and he passed along the ones suitable for younger ears. My brothers especially liked the gruesome stories.
One story he heard was about the "Tree of Death," or "Arbol del Muerte." This was supposedly a tree that had large, mean, ugly ants living inside it, and if a man fell asleep under such a tree, he would be eaten alive by the ants. The sap from the tree, dripping on his skin, was a sedative, assuring that he stayed asleep or paralyzed while all this eating was going on. Overnight, a man, his donkey, and his leather shoes could all be reduced to a bit of debris and two skeletons. When I was older, and we had returned to the States, my brothers told me stories about men who had been eaten by the ants of the Tree of Death. Of course they also told me about giant girl-eating spiders living in our attic. By the time I was in grade school I had learned to disbelieve pretty much everything they told me.
But when I entered graduate school, I took a class in tropical ecology and found out the basis for the story. There actually is a New World tropical tree with ants living in it. The ants are almost ½ inch long, aggressive, and can give a painful bite. They are not really able to strip a man to bones overnight. Of course it might feel like you are being eaten up if you get a few dozen of these insects in your shorts.
The trees are called swollen thorn acacias. Most acacias have bitter alkaloids that make them toxic to herbivores. But the swollen thorn acacias rely on their ant partners for protection. Their large thorns are hollow at maturity, perfect for ant barracks. They produce two kinds of ant food. One is a sugary nectar that leaks from the leaf stalks. The other is a high protein tidbit, called a Beltian body. There is no apparent reason for either food to be produced except to feed the ants. As far as I know the sweet sap will not sedate you.
The ants are excellent protectors. If an animal eats the tree's leaves, the ants on that branch release a pheromone, an airborne chemical that alerts all the other ants. They all rush out at the same time and bite the herbivore until it goes away. A few bites in the mouth and on the face would discourage me, too. Soldier ants patrol the area around their tree, and chew up any seedlings of other trees, that might grow up to shade out their acacia. The trees with ant colonies are better competitors in the forest, and grow up tall and healthy, while the uncolonized ones are feebler and usually don't get very big before they are eaten or shaded out by faster growing species.
The truth about the Trees of Death strikes me as a better story than the one my brothers told me. The intricate relationships that Mother Nature invents are so astonishing that they need no additional embroidery.
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