Symbiosis

We are one acting as many.

We are many acting as one

Once and awhile comes a love like none other. Two beings made for each other. Each and every thing they do fits together in perfect harmony. Totally supportive in every way.

With a love like that, anything is possible.

How many different kinds of relationships exist between beings? Let me count the ways.

Predation leaps to mind. One life form devouring another. All animals do it, developing some of life's most fantastic adaptations.

Disease and Parasitism, little monsters preying on their hosts from the inside out, eating a little bit more each day. A very popular relationship, hugely common on our planet, refined into some really bizarre relationships with complex life cycles involving multiple hosts and complete changes in body, form and function.

Symbiotic relationships; where organisms live together and both partners survive.

Commensalism

Commensalism is where two organisms live together but only one really benefits. In other words, one of the pair is a freeloader.

For example Pearl fish have a very kinky relationship with sea cucumbers. They slide their pointy tail into the anus of a sea cucumber and slither inside to hide out during the day.

Much more common commensals are critters who live on or attach to other creatures for protection, access to food, or transport..

For example a tiny shrimp in the arms of a feather starfish, or crinoid. The shrimp has evolved to blend in perfectly with the filter feeding crinoid so it not only invisible to shrimp lovers but it also gets to nibble on some of the plankton captured by the crinoid.

Hermit crabs use shells of dead gastropods as protection.

Remora Fish hitch hike on sea turtles and sharks without causing them any harm.

Mutualism

Mutualism brings two creatures, like clownfish and sea anemones, together. This is a nice relationship. Right out of one of those "how to achieve happiness with your partner" books.

Mutualism is everywhere you look on coral reefs.

The clownfish, feeds and protects the sea anemone in exchange for protection. If danger threatens the fish it will race into the tentacles and vanish amid hundreds of stinging tentacles.

The clownfish actually trains the anemone not to sting it. Each clownfish introduces itself to its partner over a period of months when the fish is very small. A special protein in the mucous of the scales identifies the particular fish.

Cute little neon gobies wiggle-dance to attract big fish of many different species. The big fish open their mouths, the gobies swim in and eat the parasites from the gills of the big fish. The gobies get a meal of parasites, the big fish get cleaned. It's clear, watching this, the cleaning sometimes hurts the big fish, they wince but don't bite.

Most coral reef fish have a mutual relationship with the corals.

They swarm above the coral eating tiny critters called zooplankton and dash down to hide in the branches of the corals if danger threatens and in return the fishy waste pellets are designed to drop down onto the coral's little upturned faces providing the corals with much needed phosphates and nitrates.

Obligate Symbiosis.

All these relationships can be classified as symbiosis - from sym - together and biosis - living. Symbiosis networking has played a critical role in the evolution of life on Earth. But there is one super special kind of Symbiosis where both partners are absolutely and permanently wed. Biologists call these Obligate Symbionts.

Obligate Symbiosis is the big special love where two beings join together in perfect harmony. Forever.

They become one; living together, changing together, staying together for all time. This is different from any other kind of relationship. Love like this does not happen often. In a world full of predation, disease, parasitism, mutualism, commensalism, and stoic, uncaring loneliness, misunderstandings are more common than total understanding. But when it does happen it changes the whole world.

The Love Bugs

The Greatest Love Story on Earth

Once upon a time, billions of years ago, the world teemed with thousands of different kinds of tiny creatures each locked in a continuous struggle for survival. They fought with fierce determination, inventing highly sophisticated molecular weapons to attack and defend against one another.

Among these microbial warriors, one creature called a cyanophyte developed a particularly insidious weapon: a chemical system to manufacture a deadly poisonous gas called oxygen. They released this toxic gas into the sea, annihilating almost all of their enemies. But life finds a way, and another bacterium created a method to detoxify oxygen by combining it with carbon, producing carbon dioxide and a high-octane fuel called ATP. This ingenious bacterium with a knack for survival, would eventually become known as the Mitochondrion Love Bug.

One day, on the edge of a great continent that has long since disappeared, a formidable bacterium, a veritable battleship of the microbial world, captured and devoured one of these Love Bugs. The Love Bug’s defenses were robust, preventing the giant from digesting it. In response, the larger bacterium built a force field made of complex lipid molecules, imprisoning but not harming the Love Bug. Surprisingly, the Love Bug thrived in its new environment. Food was abundant, and it had everything it needed. It grew fat and happy, dividing into two, and then four, and so on.

The giant bacterium, now home to many Love Bugs, was ecstatic. It could effortlessly harness the ATP produced by the Love Bugs, a high-octane energy source. Even better, the Love Bugs detoxified the highly poisonous oxygen. To get more ATP, the bacterium only needed to provide sugars, easily available from the cyanophytes, the blue-green algae that thrived in the oxygen-rich seas. These cyanophytes covered the oceans in thick mats, blissfully unaware of the symbiotic relationship developing nearby.

This grand bacteria, now called eukaryotic cells reproduced by dividing in two, and the mitochondria love bugs divided at the same time ensuring each daughter cell inherited some of the precious mitochondria. Over time, these giant bacteria discovered they could become even larger if their progeny stayed attached, and they formed an organized community of individuals. This new multicellular entity ventured into the vast mats of blue-green algae that coated Earth's seas, unafraid of the poison gas, oxygen, which had become their ally rather than their foe.

The eukaryotic cells fed on the cyanophytes and multiplied, populating the oceans with their kind. The cyanophytes, though developing many other defenses, gradually succumbed to this new, formidable organism. The once turbid seas became clear as the great mats were consumed.

And so, from a primordial battle for survival, a beautiful symbiotic relationship was born. The mitochondrion Love Bugs and their giant bacterial hosts joined forces, giving rise to the eukaryotic cells that would eventually evolve into the diverse and complex life forms that inhabit our planet today. The oceans, once a battleground, became a cradle of life, nurturing the genesis of a new era of biological diversity.

The Chloroplast

Perhaps a million years or so later, one of the of the predatory cell offspring engulfed the a cyanophyte and it became a chloroplast. Like the mitochondrion, the chloroplast could not be digested and the cell placed it in a force field prison and would not release it. The chloroplast produced lots of oxygen and sugar. The mitochondrion love bug took oxygen, sugar and water and transformed it into more energy and carbon dioxide. The chloroplast took sunlight, carbon dioxide, and water and turned it into sugars. The two love bugs were all the big cell needed, other than access to water and some essential minerals that were common in Sea.

Instead of chasing all over the oceans hunting, the big cell could simply float about in the surface waters and relax while the chloroplast and the mitochondrion did their harmonious best to make everyone happy. The big cell didn't have to do much more than protect the two of them from harm, and it designed bigger and better force fields made from a remarkably tough molecule called cellulose to fend off attacks by other predators. This union worked well and the cells evolved into all the plants on Earth.

The big cells with only one love bug - the mitochondria - learned to be - evolved - into all the animals on Earth, keeping up with the constant improvement in plant defense by inventing new ways to harvest them.

The love bug symbiosis was so perfect they have not changed very much in the billions of years the cells have cherished them. The cells have evolved into all the wonderful display of life on Earth, and the love bugs remain happily engaged in their relationship.

Love bugs reproduce by dividing. The cells don't make them. They divide and divide again in perfect harmony and balance with the cells. This means that the love bugs in every form of life on earth are the original issue love bugs. I mean, the love bugs in every cell on Earth have never died. Each one is at least two, perhaps three billion years old.

Love Bug Mark II, Zooxanthellae

There is another love bug. A long snake-like bacteria that is a powerful swimmer. It is called a flagellum or sometimes a cilia. At some point in time, many different kinds of cells began using flagella or cilia as whip-like propellers to speed them through the water. One of these cells, called Gymnodinium, became a second level love bug, one in great demand by some 650 or so reef building corals, 6 species of giant clams, a scattering of gorgonians and a flatworm.

Corals hunt the Zooxanthellae love bugs just after they form into microscopic swimming planulae larvae. When they find the Gymnodinium, they absorb it (or the Gymnodinium infects the larvae, nobody knows who initiates the relationship).

The Gymnodinium drops the flagellum and becomes a rounded cyst. The cysts are called zooxanthellae. About 8000 could fit on the period at the end of this sentence. Special amoeboid coral cells grab hold of the zooxanthellae and carry them through the quickly growing coral polyp.

They shove the cysts between other coral cells, just under the outer skin cells where they can get the most light. The zooxanthellae divide and divide again, forming a thick garden of brightly colored cells crammed between the coral cells. Eventually, the zooxanthellae outweigh the coral cells by about three to one. All of the rich colors of tropical corals come from the zooxanthellae - the coral cells are transparent.

If the coral is put into a dark room, it rejects the zooxanthellae, spewing them out into the sea water with long strands of mucous. The coral continues to live and, if replaced in the light again, it can become repopulated by zooxanthellae.

The coral does not (at least not normally) eat the zooxanthellae in its system. The coral polyps use their tentacles to catch other kinds of small creatures from the sea and they capture pellets of fecal material dropped by fish schooling over the reefs. The captured food and fecal material is rich in phosphates and nitrates. These fertilize the zooxanthellae.

The coral cells produce carbon dioxide, nitrate and phosphate as waste as do all animal cells. The zooxanthellae, nestled in the coral tissue, take these waste materials and use them as food. Using sunlight, they convert the coral wastes into carbohydrates and oxygen. Both they and the coral cells use these to energize the complicated job of rearranging the elements of sea into their form, to maintain vigilance, move and reproduce as needed for survival.

Relationships depend on different viewpoints

Zooxanthellae as parasites

A century ago, biologists classified corals with plants. When they discovered the relationship of coral and zooxanthellae they thought of the zooxanthellae as parasites. Even today, some biologists talk about corals becoming infected by zooxanthellae. This was a perfectly reasonable view. Looked at from the standpoint of the zooxanthellae, the coral was a host. They entered the host and multiplied, filling every available space. The coral provided food and shelter. The growth pattern of the coral was modified by the influence of the zooxanthellae to maximize sunlight exposure for the benefit of the parasites. If things got tough, the zooxanthellae could escape into the sea.

Zooxanthellae as cultured plants

Other scientists thought the corals farmed the zooxanthellae. Seen from the perspective of the coral, the zooxanthellae were slaves. The coral cells captured and arranged them in their tissues. The coral cells obviously farmed the zooxanthellae to provide themselves with food and oxygen. The method is so successful a coral colony produces more food and oxygen than it can use by itself. These are released into the sea water and help support the other reef creatures around them.

Zooxanthellae as Partners

Then a third viewpoint was proposed to satisfy both schools of thought. The coral cells and the zooxanthellae both benefited from the association, a phenomenon already known in lichens. This mutual association in plants was called symbiosis (living together) and the concept seemed to fit well with the coral-zooxanthellae relationship. A great deal has been written about corals and zooxanthellae from this viewpoint and everyone agrees this is the best way to look at the association.

But there is another viewpoint.

Corals and Zooxanthellae as One Concept

At some point in the distant past, coral cells and zooxanthellae learned to live together. This association changed them forever in basic ways. Over the millions of years they have lived together, the corals learned ways to behave to increase their survival in particular circumstances.

Some became flattened, some massive, rounded colonies, some grew big polyps, some grew polyps so small they look hardly different than the skin connecting them. Some became blue, some brown, some green, some yellow, some orange.

Each new behavior pattern was etched forever in the genetic memories of the individual lines of coral behavior, never to be forgotten. Today, there are about 650 species of reef building corals, each one living in special niches on the coral reef. The coral colony we see on the reef today is the result of millions of years of evolution.

Throughout all those years, the way the coral grew, the behavioral network of the polyps, the intercommunications between cells, included both coral and zooxanthellae.

The reef building corals we see today would never have evolved without the symbiotic relationship between the corals and the zooxanthellae.

The corals and the zooxanthellae are not separate beings, they are a single intercommunication reacting with the surrounding environment in a unified effort to survive.

This view sees the coral colony as a continuous web of intercommunications extending between the zooxanthellae, the coral cells, and the other creatures of the whole coral reef ecosystem.

While it's true we can remove the zooxanthellae and the corals can live without them for awhile, this is only a temporary interruption in the web of communication creating the existence of the coral. On the coral reef, at night, the loss of zooxanthellae produces a drastic drop in oxygen levels and if the association is not renewed quickly, the corals and many other reef creatures die. This is, in fact, a major problem for today's coral reefs. In the late 1990's corals began ejecting their zooxanthellae in response to elevated sea temperatures. This "coral bleaching" epidemic resulted in massive die-offs of the coral reefs of the Pacific and Indian Oceans.

From the viewpoint of the webs of intercommunication creating the coral colony and the coral reefs, the zooxanthellae and coral cells are a single concept, intercommunicating in perfect harmony.

Symbiosis is still a useful term, but only with a focus on the relationship, the intercommunications, and not the "individuals".

Not forgetting that the "individuals" involved, coral cells and zooxanthellae, are themselves intercommunications of the earlier appearance of the most perfect love affair on Earth; the eukaryotic cells with their mitochondria and chloroplast love bugs.

Evolution

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