Nature Notes: The Pushes and Pulls
I’ve been hatching out Salt Lake brine shrimp eggs in local seawater for a year and a half. At room temperature, they hatch out into swimming in two days and at about a tenth of a millimeter in length they are barely visible to the naked eye. They are called “nauplii” and are orangish. I feed them to mosquitofish, which I keep in aquariums. I raise a few to adulthood in Rubbermaid totes set on my patio filled with seawater. Their scientific name, Artemia salina, says it all, they tolerate and breed in water of very high salinity.
It is easy to gather the young from the pans in which they hatched. They move to spots with the most light, either incadescent light or sunlight, leaving the empty egg casts behind. Animal behaviorists would describe them as phototactic, meaning they are attracted to light and move toward light. Larvae of some marine invertebrates move away from light; they are said to be photophobic. Some fish are thermotactic, they move to areas of warm water such as the cooling waters emanating from nuclear power plants situated next to large bodies of water such as the Long Island Sound.
Almost all green plants are phototrophic, they grow toward the light, away from the dark. Many lianas such as Virginia creeper, fox grape, and bittersweet are phototrophic to the degree of following the sun around as it moves from east to west relative to the earth; thus they curl upward around tree trunks, following the sun as they go. Some trees in dense stands, such as Douglass firs, actually twist their trunks in the direction of the sun. Does it make them more resistant to strong winds?
Most plants are also negatively geotrophic, or geophobic. They grow against gravity, while their roots are geotrophic, they grow down. What would green plants do on the moon, where there is very little gravity? They would all be bonsai-ed, no doubt.
It’s an either-or world. You either are or you aren’t. Some people are agoraphobic: They don’t like to be in crowds. I would never make it through more than a few minutes of waiting for the ball to drop in Times Square on New Year’s Eve. I am also claustrophobic, which is similar to agoraphobic; I can’t go into an M.R.I. machine headfirst. When I was in the Army and was loaded onto the back of a semienclosed truck with about 20 others tightly packed, I had to fight my way to the very back of the truck bed or I would have started screaming. Maybe that’s why I and many others would rather walk alone in the outback or stand by ourselves at the foot of the ocean.
Many spiders and other insects, invertebrates, and even some mammals are thigmotactic. They are drawn to spots where their bodies come into multiple contact with different surfaces such as between pieces of wood and the bare earth below. In such cases the organisms are both thigmotactic and negatively phototrophic. Which force is strongest is a matter for scientists. You often find spiders, especially daddy longlegs, in corners where two walls meet the ceiling—three surfaces—the perfect spot to put down their threads and wait for prey, especially prey that is equally thigmotactic.
Many humans, including myself, sleep with their knees drawn up and their upper bodies curved toward their knees in the so-called fetal position. Still others, like me, will close their hands tightly while they sleep, or have one or both hands touching the face, maximizing the touch factor. My daughter-in-law and her son, my grandson, both sleep with one hand pressed against the side of the head, cupping it, so to speak, just as I do. Genetic or not, it is not an uncommon trait. I suppose a psychiatrist could explain the fact that I am both claustrophobic and thigmotactic; the two tendencies would seem to counter one another.
All living things, including plants, have some kind of push-me-pull-me set of reactions to different stimuli, whether they be sound, light, odor, or other. There are now seven billion of us humans; if we were all agoratactic to the Nth degree, we would crush one another in a compact mass the way dark stars do. Ouch! Every day one reads in the newspapers or on the Internet about instances of humans trampling one another fleeing from a fire or even trying to get into a rock concert or soccer. On the African veldt or Western prairie they call such actions “stampedes.” Such attraction-avoidance behavior can simultaneously have both survival and anti-survival value.
I’m sure the reader has noticed that on the Long Island Expressway or Los Angeles freeways some people hug closely to your rear end to the degree that they are almost touching it, say, as the professional racecar drivers do on the speedway. It even happens on local roads like Route 114. Agorataxis or not, I find it extremely unbecoming, if not frightening.
In the final analysis, we are not so different from the rest of the fauna, minute or large, sedentary or locomotory. We have this or that tropism or taxis, we respond to this or that stimulus in this or that way. If, indeed, we among all the billions and billions of the others have free will as many philosophers and psychologists contend, we manifest it despite the omnipresent pulls to and pushes from the thousands of collective stimuli acting in any one moment. It’s almost too much to ponder. I can only sit and wonder.