6. Panic Among the Earthworms

I have often been struck by the abundance of what, at first encounter, seem to be rather mundane stories of the success, tragedy and survival observable within the natural world. These are incidents which, upon further examination, are revealed to be anything but ordinary. Often these dramas are there for the partaking and require nothing more than attentiveness on our part, though sometimes it helps to add a dollop of luck. At other times, the interactions of things wild are more subtle and seeing them requires the practice of patience, stealth, and a bit of hard work. Whichever the case, what is often revealed are behaviors or ecological interactions that are far from commonplace and are astounding in their complexity. Take the lowly earthworms for example. I speak of Lumbricus, Aporrectodea, Diplocardia and their ilk. Local fisher-folk may refer to them as night crawler, red worm, wriggler, or dew worm. Earthworms belong to a widely distributed and biologically successful group known as the annelid worms. They are so-called because of the division of the body into small, ring-like segments (annuli). Leeches and certain marine worms are also annelids. But it is earthworms that are involved in this story.

The students in my introductory biology classes were often astounded at the complexity of these little animals. I suppose they had presumed that worms were simply long, tubular creatures which were full of some sort of unidentifiable black mush. They also had likely assumed that the worm’s main purpose was to repose at the end of a fish hook. However, upon opening the body cavity of an earthworm they were amazed to find a brain, a ventral nerve cord, several hearts, a muscular pharynx, a crop, gizzard, lengthy intestine, and a collection of rather complex reproductive organs – both male and female actually. Incidentally, the student’s newly found awareness is one of the reasons I supported the idea of doing dissections in a biology or zoology class. Many argue that it is inhumane and teaches children to devalue life. I see it as the exact opposite. How could one peer into an animal, which minutes ago was perceived as nothing more than an inert rubbery tube, only to find an extreme intricacy of organ systems and thus not be more appreciative of the anatomical sophistication and physiological elegance of any living organism?

Earthworms breathe through their skin by diffusion and thus must remain moist. This is one reason their skin is so liberally impregnated with mucus glands. As a result, handling them is a bit of a sticky endeavor. They have no eyes but are quite sensitive to light via their skin cells. Staying out of the light helps prevent drying of the skin, which could lead to suffocation, and lessons the chance of being seen by a predator. Since they operate mostly in a world devoid of light, earthworms are highly sensitive to vibrations within the soil. All in all, I find them mighty impressive.

No less a scientific giant than Charles Darwin spent years studying the behavior and ecology of earthworms.  In fact, the last book he published dealt with this subject. Darwin pointed out, as others have since, that earthworms may play a valuable role in nature. Their tunneling forms passageways for oxygen and water to enter the soil. Their waste products, mucus slime, and dead bodies fertilize the soil. This is well and good within a lawn or garden. However, more recent studies have shown that non-native earthworms, of which Indiana has a few, may be detrimental in forests where their overabundance can reduce soil fertility and thus diminish the number of native plant species present.

Earthworms, as you might guess, are a food source for a variety of animals. These range from the robins one sees hopping about in the yard to the moles lurking below the surface. Ah yes, moles; now we come to the crux of this story. I’m afraid moles are most often thought of by humans in the most negative of contexts. I must admit that skimming over one of their raised tunnel rooves while mowing and thus removing a huge clump of sod from a well-manicured lawn is aggravating. However moles are highly beneficial for soil aeration and water uptake in the same way as earthworms. Home owners often blame them for damage to their plants but moles are innocent. The fact is they are voracious little carnivores. Scarab beetle larvae, ants, ground beetles are all fair game. But guess what animal constitutes their favorite prey? If you said, “What are earthworms?” the Jeopardy prize is yours.

With some effort, I’ve tried to imagine the life of an earthworm. Can you too picture yourself creeping along a tiny, claustrophobic tunnel in a cool, damp world totally bereft of light? This is a Stygian realm, dark and forbidding as Miller’s Cave. There are monstrous beasts here; gigantic, furred creatures with but one thought on their minds – the securing of a nice meal of earthworm. We are blind and without defense in this gloomy world. Slowly inching forward by taking mouthful after mouthful of soil; it would be fortunate that our tiny brain could not foresee the inevitable, gruesome end as three dozen sharply pointed teeth render us into mole fodder.

That was the image that originally existed in my mind regarding the subterranean interaction of moles and earthworms. I saw the worms as little more than slowly moving targets waiting to be consumed by the much larger, more intelligent, and vastly more powerful mole. I’m afraid I had underestimated the behavioral potentials of the earthworm and the power of natural selection to shape them. This is how I came to that conclusion.

Standing in my flower garden, I was leaning on my rake taking a well-deserved break from a morning of tilling and planting. Idly glancing down at the ground, I was quite surprised to see three earthworms suddenly appear onto the surface and begin to crawl rapidly away from the spot from which they had emerged. If one could apply the term run to animals without legs, this was such a case. They seemed to be fleeing for their lives as if in a state of terror. As I watched them speed away, another sight caught my eye. Within a foot of where the worms had emerged, the soil was making periodic, upward, pulsations. It was an eastern mole paddling its way through the topsoil.  I really was quite flabbergasted as I made the connection between the emergent flight of the earthworms and the sudden appearance of the mole.  It was rather obvious that the worms were sensitive to the vibrations produced by the approaching mole and had taken to the surface in a last ditch effort to avoid becoming a meal. To me this seemed a remarkable piece of behavior from animals with a brain about the size of the period at the end of this sentence. If the worms recognized the vibrations as a threat, did this imply that they could remember? Didn’t this behavior suggest not only the capacity of memory but, more specifically, the ability to recall that the vibrations were produced by their arch nemesis, the mole? Did this indicate that they then had to analyze this memory and decide upon an appropriate response? In other words, were they actually capable of advanced neural integration? I don’t want to be anthropomorphic but the earthworm equivalent of memory, integration, and response borders on what I had always assumed were marks of intelligence. Darwin, in his aforementioned studies, devised experiments to observe how worms handled leaf material of different shapes. The results suggested to him that they did possess intelligence. He compared their abilities to the highly developed dexterous sense possessed by people who are deprived of sight.

To me, the fact that such high powered sensory effort could be accomplished by an animal with such a primitive nervous system was stunning. What was going on within that relatively tiny accumulation of neurons? Some might say, well it’s just instinctive behavior. But, what does that mean? It only opens another series of questions. What is instinct? Yes, I know that instinct is an inherited behavior but how then does a neuron convert DNA code into a physical behavior? How does an earthworm, or a human for that matter, store the information needed for an instinctive response in a cell that for all intents and purposes is no different than a skin cell? Neurons, like skin cells, have a cell membrane within which is the cytoplasm. This is mostly water. Scattered within this protoplasm is a collection of organelles such as the nucleus which acts as the cell’s control center. There are mitochondria for energy production and ribosomes for synthesizing proteins. Where, and how, on earth does a worm store a memory of what the vibrations of a mole feel like? For that matter, how do we store the memory of a favorite song, a list of phone numbers, or the recollection of a favorite vacation spot? I’ve read that neurobiologists explain memory as the repeated use of certain nerve cell processes.  I’m still left in the dark. What does that mean? If I could miniaturize myself, like the crew in Asimov’s Fantastic Voyage, and actually look at a stored memory, what would I see? Would the recollection, implanted those many years ago, of my wife’s first kiss exist as a huge organic molecule of some sort? Would it be a dendrite somewhat thicker than all the others protruding from a brain cell? Would one nerve cell, or a group of them, have a plethora of dendritic extensions compared to others? Somehow, in trying to understand the magnificence of memory and brain function, whether in earthworm or man, I arrive at an impasse. I can go no further in my attempt to comprehend either the biological or the transcendent marvel of it all. Contemplating the maneuvering of the little earthworm trio certainly opened a world of wonder for me.

So here we have it, a remarkably complex escape behavior in an animal we all too often view with total indifference, if not disdain. And lying beyond that, a doorway into the curious world of instinct, memory, and intelligence is opened. The whole earthworm/mole encounter forced me to contemplate how many other phenomena of the natural world have rested at my feet, unnoticed through simple inattention. All in all, such chance meetings serve as illustrations of the incredible complexity of interactions that make a typical ecosystem such a marvel to behold. If only we take the time, give ourselves the opportunity. Observations, which at first glance seem so simple and straightforward, will often compel us to consider in even greater depth just how multifaceted, entertaining, and extraordinary is the living world we inhabit.

A Postscript:

In investigating the fascinating phenomenon of earthworms responding defensively to the presence of moles, I ran across an interesting way in which humans capitalize on this behavior. It seems that quite a few folks were way ahead of me in being aware of how earthworms respond to vibrations in the soil. This is a very handy piece of knowledge if one is interested in collecting bait for fishing.  Ever hear of worm grunting? Check it out.



5. From So Simple A Beginning

. . . from so simple a beginning endless forms most beautiful and

most wonderful have been, and are being, evolved.”

Charles Darwin







A few of you may recognize the story told in my first blog. I have told it before. On the surface, this story describes my first nocturnal venture into the tropical rainforest of Southeast Asia. But, of course, I really intended for it to mean more than that. I related the tale for three reasons. First, it is my belief that the natural world offers us limitless opportunities for learning, wonder, pleasure, and fulfillment. These opportunities give us the chance to indulge in self-reflection, accumulate knowledge, escape from world-weariness, and provide a pathway to understanding our place in the world. Such activities are particularly human ones. Indeed, I would argue that these types of mental gymnastics are what set us apart from other species. We may be members of the animal kingdom but it appears that we are exceedingly special animals in this respect.

Secondly, it seems that both anecdotal and experimental evidence now suggest that contact with the natural world is vital for the psychological health of humans. For millennia, it was the natural world – the rainforest, the prairie, the desert – that provided the environments within which our human proclivity for curiosity, inventiveness, contentment, and meaning were satisfied. Achieving these desires brings us a sense of satisfaction and happiness. They make our life whole and purposeful.

And finally there is this – the big-picture idea – to consider. It is now apparent, after five-hundred years of progress in science, that the world in which we live is part of an astonishing, I would even say miraculous, emergent process. I have long wondered why is there is something rather than nothing in the first place? If all we know has emerged from nothing, what is this “nothing”? Was it the absence of space? The absence of time? These are questions that have occupied the minds of scientists and philosophers alike for a good while. Whether the question is valid or what the answer to this enigmatic query might be (if one is possible), one fact seems clear. From a state of virtual nonexistence has materialized a world of incredible complexity and biodiversity. Some will disagree with my belief that cosmic and biological evolution have direction. Others will accuse me of making a leap of faith. Still, I would argue that the evolution of the universe, and subsequently earth’s biodiversity, do display both purpose and direction. From the spawning of the first simple element hydrogen, emerged the stars that populate the billions of galaxies of our universe. From some of these stars, the elements that, so far as we know, comprise all matter were then generated. The calcium in our bones, the nitrogen in our DNA, the gold filling in our tooth, all these have been forged from the titanic forces generated by exploding stars. Once formed, the elements have yielded molecules and compounds which have made possible the evolution of life itself. From the first primitive cells, whose precise origins are lost in the vapors of time, have arisen all of the organisms, simple to complex, which have graced the earth.

Over its four and one-half billion year history, our planet itself has undergone extreme emergent geologic change. From its molten origins has come a world of rock, soil, air, and water. As a boy, exploring the waste from the numerous underground coal mines near my home in southwestern Indiana, I found evidence (in the form of bivalves and crinoids ) that the land I now walked upon was once the bottom of a sea. Further east the Appalachians had risen to snow-capped heights rivaling the Rockies. Over the eons, the ravages of wind, water, and ice have reduced them to their present aspect of rounded, rolling domes – the Smoky Mountains. The very continents themselves, we now know, wander restlessly over the earth’s mantle. Viewed from space, the visage of earth today is very different than when the dry lands were merged to form the immense super-continent known as Pangaea.

Within the realm of living matter, the emergent complexity and increasing biodiversity we see is perhaps even more remarkable. The ancient archaea and bacteria, their simple cells lacking even a nucleus, first arose billions of years ago. Soon they inhabited the soil, water, and rocks of the earth. Seemingly no habitat was too extreme and even the hot springs and salt lakes teem with these so-called extremophiles in their untold numbers. Then the more complex nucleated protists, the algae and the protozoans took their place upon life’s stage. The algae began the first tentative movements of life onto the dry land. These colonizers in turn gave rise to the primitive plants, such as the mosses, and eventually to complex autotrophic organisms such as the cone-bearing and flowering plants. The latter group, owing to their great biological success, clothed the earth with photosynthetic greenness. Their leaves, pollen, and nectar provided sustenance for a vast assemblage of heterotrophic species and thus triggered an evolutionary explosion of diversity within the animal kingdom.

With my apologies to plant lovers, I now follow the trail to the animal kingdom. From animal-like protozoans extended a pathway to the jellyfishes, corals, and sea anemones. Even today, their stinging-cell armed descendants constitute the cnidarians which swarm the seas of the world and build the limestone bulwarks we call reefs. Some six hundred million years past the multitudinous and varied realm of the worms emerged onto the ancient scene. Flatworms crept through marine and fresh waters. Many of their descendants became adapted to a parasitic lifestyle and comprise the fascinating clans of the flukes and tapeworms. Roundworms filled the soils of Earth in their millions. The segmented worms too found their places in both the aquatic and terrestrial abodes of the world. Today they reside as marine tubeworms, earthworms that till the soil of your lawn, and the sanguivorous leeches. Mollusks, in their remarkable and diverse forms from squid to snail, began to swim, crawl the sea bottoms, and to probe into the dark, moist places of terra firma. That great assemblage of animal species known as the arthropods appears in the fossil record some five hundred and forty million years past. They claimed their portion of the aquatic environments of the world in the shape of shrimp, crab and lobster. In the guise of centipede and scorpion, spider and insect the arthropods also came to be the dominate invertebrates of the dry lands of the planet. Today nearly one million species of insects alone are known to science. The echinoderms, the spiny-skinned starfish and urchins, in their rich variety dispersed themselves through the earth’s vast oceans. Descendants of this group became the ancestors of the fishes which eventually claimed dominion over the waters of the world. From one group of ancient fish antecedents came the audacious back-boned creatures which first climbed from the water and into the forbidding world of air and sun. Thus, the first amphibians evolved some four hundred million years ago. Over the next three hundred million years there emerged the reptiles, the birds, the mammals. For over one hundred and fifty million years, the dinosaurs reigned as the dominant group of terrestrial vertebrates. The sudden extinction of the dinosaurs allowed birds, descendants of theropod dinosaurs, to take a turn as the most biologically successful of vertebrates. They were joined in this new world order by the mammals, themselves descended from reptilian ancestors known as synapsids.

It isn’t just the emergence of such varied and abundant forms which astounds me. It must be remembered that none of these organisms exist in isolation. We have also seen the emergence of a hierarchy, like a set of nested boxes, of interrelationships. Organisms form populations, populations give rise to communities. Communities and their nonliving environment have been organized into ecosystems. Ecosystems comprise the biosphere, the thin living shell which surrounds the earth and within which all life is found. The interactions within the ecosystems of the world are complex and varied in the extreme. So much so that even today, in the twenty-first century, we cannot claim anywhere near complete understanding of all their workings. British poet Francis Thompson must have intuitively sensed this when he wrote “All things . . . hiddenly connected are. That thou canst stir a flower without troubling of a star.” All this from a great mass of hydrogen spawned from a Nothingness.

Among the mammals, one group was special. The hominids, with their tremendously developed cerebral hemispheres, rose to prominence. Within this group was a modern species known as Homo sapiens  –  us. And here, after fourteen billion years of evolutionary progress, a true miracle occurred. . With the appearance of humans, the universe has now, finally, at last become able to contemplate its own evolutionary history. We are, as Carl Sagan so aptly put it, “stardust contemplating the stars”. I find this revelation fulfilling. It is the antithesis of the argument that life is purposeless. Can miracle be too strong a word for what has occurred? In an online dictionary, I find the word miracle defined as: a highly improbable or extraordinary event . . . that brings very welcome consequences. In my contemplation of life on earth, this seems to fit what has happened. I find the mere fact of my own existence, let alone the plethora of earth’s organisms past and present, extraordinary. I certainly consider the wondrous biodiversity of our planet a welcome consequence. It is vanity I suppose that compels me to also consider my own existence a welcome consequence of the unfolding universe story.

In the end, our world and its origins and its complexities, still provides puzzles and enigmas aplenty. As I have aged, I have found myself somewhat more willing to acknowledge that perhaps this big brain of ours isn’t really big enough after all. Like a little Commodore 64 that has been asked to solve a complex problem in celestial mechanics, our brain simply isn’t up to the task of totally comprehending the immense mystery and splendor of the cosmos. Charles Darwin had the following to say about our contemplating the enigmas of the universe. “I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton.Darwin was correct about a good many things. Perhaps he was in this case also.

And so, I must be content for now with the idea that one of our most important purposes in life is simply to engage with and appreciate the living world around us. I have previously voiced my congruence with Alfred Russel Wallace who offered this simple foundation for achieving meaning in our lives. Said he, “Can we believe that we are fulfilling the purpose of our existence while so many of the wonders and beauties of the creation remain unnoticed around us?”  And there are wonders at every turn.  We should marvel at the beauty and humbling immensity of Orion, faithful companion Canis Major at his heel, as they wheel through the blackness of the winter sky. We ought to find our breath taken away by the flash of a blue morpho’s wings as it wheels through the rainforest understory. We should stand awestricken before the spectacle that is a giant sequoia.  Perhaps we cringe, but we should also ponder with admiration the exquisite relationship of parasite and host, of predator and prey. We should marvel at the little ruby-throated hummingbird that has traveled a thousand miles to once again find the feeder we have proffered. We ought to stand in amazed meditation as wave after wave of sandhill cranes descend, on parachute-like wings, into their marshland roost. All of these phenomena are part and parcel of the Universe story. So are we.

We know so much more than our great-grandparents did. We now understand that the very deoxyribonucleic acid which carries our genetic code represents an immortal thread. Our DNA embodies a strand that is a shared lifeline stretching back through the temporal history of the evolution of life on earth. We now appreciate that we have DNA sequences that are communal, not just with other humans, but with most other life forms on this planet. Perhaps this is why the natural world, given the chance, can be such a wellspring of joy, contentment, entertainment, and meditation. We are hard-wired into interrelationships with other species. The natural world is our world, our home, our birthplace.

This is why I consider the opportunities for emotional, psychological, and spiritual wholeness provided by contact with nature to be treasures of rare and lasting value. This is why I feel myself compelled to unabashedly jump with both feet into my experiences in nature.  I want to see the earth through the stalked eyes of fiddler crab, imagine the world through the super-senses of bird and bat, to feel the tug of tide and pole. Like Leopold, I envy the muskrat lying eye-deep in a marsh, eavesdropping on the loquacious geese. I want to follow Thoreau’s advice and suck the marrow from nature’s bones.  I want to come closer to Henry Beston’s understanding of animals not as underlings but as, “other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendor and travail of the earth.”  Yes, had I a hundred lifetimes, I reckon there would still be too much to see, to ponder, to appreciate,  to leave me in besotted admiration of the miraculous wonder that is life on earth.

Photo Credits:

Darwin's Tree of Life - Charles Darwin [Public domain], via Wikimedia Commons'
Phylogenetic Tree - By Maulucioni y Doridí [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons
Hubble Deep Field - By NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team [Public domain], via Wikimedia Commons'
Crinoid Fossils - George Sly
Hercules Beetle - George Sly
Albertosaurus & young - George Sly
Horsehead Nebula - Natl. Aeronautics and Space Admin.
Darwin Portrait - By Charles_Darwin_seated.jpg: Henry Maull (1829–1914) and John Fox (1832–1907) (Maull & Fox) [2] derivative work: Beao (Charles_Darwin_seated.jpg) [Public domain or Public domain], via Wikimedia Commons