Dr. Bortrum
09/03/2009
Deluded Insects
In this year celebrating the 200th anniversary of Darwin's birth, I've tried to avoid writing too often about evolution. However, an article by Greg Miller in the July 3 issue of Science titled "Origin of the Nervous System" did catch my attention. Arguably, the most impressive product of evolution is our human brain, with all those neurons. The big question posed in Miller's article is how did the neuron come into being? Trying to find the answer, scientists look at the early, lowest forms of animal life for clues.
A controversy has arisen in the scientific community as to what are the most primitive forms of animal life around today. Sponges and comb jellies have their champions in this controversy. Sponges don't have brains or even neurons but they do have genetic features and some of the proteins that are the building blocks of neurons. Hence the logical thesis that the sponge is the lowest form of life preceding animal life with some sort of simple nervous system.
Last year, however, some researchers claimed that their genetic analyses show the comb jellies, marine creatures that resemble jellyfish, are lower life forms than the sponges. However, the comb jellies actually have neurons and a simple nervous system. If the comb jellies do predate the sponges it would seem to indicate the sponges lost their neurons after they split off from the comb jelly line. Sounds unlikely to me but I'm no expert, that's for sure.
Leaving that controversy aside, How could a nervous system originate? Perhaps the single-celled paramecium provides a clue. In the paramecium there is an electrical effect when it bumps into something. Could a single cell be a precursor to the neuron, where ions and electrical charges flow on a routine basis? When a paramecium bumps into an object, the paramecium reverses the beating of its hair-like cilia and backs off. Get a bunch of such cells together, stick them at an animal's front end and you may have the beginnings of a nervous system and, eventually, a brain. Well, as so often happens when I start a column, it's clear that my intended subject is rather fuzzy and, in this case, certainly not as sexy as another evolutionary product, the orchid.
While the evolution of a brain is an amazing achievement, we animals were preceded by plants, one of them being the orchid. As I've mentioned before, I belong to an organization known as the Old Guard of Summit, even though we meet in the neighboring town of New Providence. Our Old Guard chapter is rather unusual in that we meet every week of the year except for the Christmas-New Year's week. Every other week, we have a meeting with a speaker; the rare exceptions being a handful of meetings featuring a musical group, a movie or video or a group discussion of some important topic. Speakers have included prominent figures such as former New Jersey governors Christie Whitman and Richard Codey and yours truly on two occasions. At the end of each speaker's talk we present the speaker with our "Orchid Certificate". When the organization was founded in 1930, Summit was a center for orchid growing and the orchid was adopted as our emblem.
I have always thought of the orchid as a rare and attractive flower. My wife wore a green orchid at our wedding some 58 years ago. I was surprised to find an article on orchids in the September National Geographic headlined on the cover "Sneaky, Sexy Orchids" and the title on the first page of the article ""Love & Lies". As an aside, I've often imagined the possibility that plants, even though lacking a brain, have some degree of self awareness. I've read that some trees, for example, give off chemical signals to other trees when attacked by bugs or diseases. But, except perhaps for the Venus flytrap, I've never considered a flower to be devious and sexy.
Well, be warned that young children should leave the room - this is indeed R- or even X-rated! The orchid, as with most plants that are anchored in place, has the problem of how to spread its genes and procreate when rooted in one spot? The dandelions in my lawn have no problem in this regard. When the yellow blooms go to seed, the puffy white seeds get carried all over the neighborhood by the wind. But the orchid is stuck and has adopted other strategies to induce various so-called "higher forms" of life to enable it to spread over six continents and multiply into 25,000 different species. Among the higher forms of life that it's seduced is us. We've bred many a species of orchid to suit our own ideas as to what makes an ideal orchid. It even convinced our Old Guard to make it its symbol!
However, long before we arrived on the scene, orchids have been hard at work convincing various insects to come pay them a visit and leave carrying pollen to other distant orchids, where the pollen may fertilize another orchid of the same type or, in some cases, create a new species of orchid. Some orchids do this the old fashioned way by providing tasty nectar to attract visiting insects. However, other orchids have figured out that they save on the energy needed to make all that nectar if they can trick an insect into paying a visit by offering the insect not nectar, but the lure of a sexual experience.
The Ophrys, known in some quarters as the "prostitute orchid", seduces a male relative of the bumblebee by mimicking the appearance and even tactile feel of a female bumblebee's behind! To the male bee, this orchid looks as though a female bee is embedded in the flower sucking up nectar; there's fake fur and the appearance of folded wings, quite a neat bit of mimicry. The scent of the orchid also matches closely the scent of the pheromones of the female bee. The male bee is hooked, approaches the flower and attempts to mate, with considerable enthusiasm. By the time he realizes that he's the victim of a tawdry trick, the orchid has plastered his back with two yellow pollen-packed sacs and off he flies to scatter the Ophrys genes, pollinating another orchid.
According to Michael Pollan, author of the Geographic article, proponents of intelligent design have used the Ophrys orchid as an example of something that had to have an intelligence of some sort design it. Strangely, Darwin himself was keenly aware of orchids and their various characteristics that deceive insects into helping to spread their genes. Of course, Darwin didn't know about DNA but just after publishing his "The Origin of Species" he followed with another volume titled "The Various Contrivances by Which Orchids are Fertilized by Insects". Some feel that had he published the second book first, more people would have readily accepted the concept of evolution.
Pollan cites one case that really stands out. Darwin was perplexed by the existence of an orchid on Madagascar that had a drop of nectar at the tail end of a foot-long floral spur. There was no way that any known insect could get at that drop of nectar so why was it there? Darwin predicted that there was a moth with a foot-long tongue that could get to that drop. Darwin died, but two decades later a hawk moth was discovered and, when the entomologists unwound its tongue, you know the answer. It was a foot long!
Finally, a really weird, X-rated case of evolution. It involves the Australian tongue orchid and the male wasp of the species Lissopimpla excelsa. Just the name of the wasp sounds sexy to me. The tongue orchid has a tongue-like labellum and also emits a scent very much like that of a pheromone of the female L. excelsa. Well, the male wasp can't resist and lands on the orchid tail first and immediately begins to copulate with the flower, pushing the tip of its abdomen down into the orchid. The orchid responds by sticking its pollen onto the wasp's rear like a couple of little yellow tails. The male wasp actually gets into having sex with a plant so thoroughly that in his ecstasy he often ejaculates into the orchid. What a waste, you might say. There's this poor deluded male tricked into having sex with a plant and there's the orchid left with a batch of wasp semen. It seems like a no-win situation.
But wait, we've forgotten about the female L. excelsa. She couldn't care less. It turns out she doesn't need the male's sperm to reproduce. This female wasp can reproduce with or without the male's sperm. But here's the catch - with the male's sperm, the female produces a mix of male and female offspring. However, if the amorous male has wasted all his sperm dallying with the orchid, without that sperm the female only produces male wasps.
This can't be a good situation for the general population of L. excelsa wasps. But look at it from the standpoint of the tongue orchid. By luring the male into going all the way, the orchid has reduced the supply of male sperm and increased the chances that there will be more males. This means more males making out with the orchid and more chances for the orchid to pin pollen sacs on the wasp tails to spread the orchid's genes.
Orchids are indeed sneaky and sexy. Of course, my brain tells me that all this talk of sneaky, devious and sexy orchids is ridiculous; after all, these are just plants. On the other hand, there's even a hint of sex concerning the Old Guard and the orchid. When we have a female speaker, she is presented with a real orchid in addition to the orchid pictured on our certificate. The member presenting the orchid is left with the choice of simply handing the orchid to the gal or the more hazardous pinning the flower on the recipient's blouse or whatever. A surprising number of our more adventurous members opt for the latter approach.
Next column to be posted on September 17. I promise I'll return to G-rated subjects.
Allen F. Bortrum
