Exploding Termites – Sacrifice of an Individual for the Good of the Whole Organism

When do the needs of the many outweigh the needs of the few, or the one, as Spock suggested in Star Trek II? I have no interest in defending the utilitarian philosophy of Jeremy Bentham, especially as a guide for understanding human moral psychology, but it is interesting to observe that some simple organisms display altruistic behavior by putting the needs of the many over the needs of the individual.

There are more than 2800 living species of termites.  All species of termites are social insects which means they employ division of labor among individuals in a single colony much like ants and bees.   Social insects are truly amazing organisms with many very sophisticated behaviors that allow the colony to complete complex tasks that no individual insect could complete themselves.   Social insects have long fascinated scientists who have published thousands of studies about their behavior and life history.

The behavior, genetics and reproductive strategies of social insects is highly varied and complex.   One of the stranger behaviors observed among many social insect species is the propensity of some individuals to self-destruct in the presence of enemies. This behavior, called autolysis, has recently been studied in one species of termites. You can find a summary of this study in this note from the journal Nature.  This report contains a description of exploding termites!  How and why  would a termite explode and commit suicide?

Researchers found that some workers of a particular tropical species of termite had bluish-banded abdomens.  The blue color is associated with the accumulation of a toxin. They hypothesized that the workers with the most blue abdomens were the oldest and had accumulated the most toxin. They predicted, based on evolutionary assumptions about the potential selective advantages of altruistic characteristics in social insects with division of labor, that the bluest, and most-toxic, members of the community  would be more willing to self-destruct presumably to subject their enemies with the contents of their abdomens.

This hypothesis was tested by introducing typical enemies of termites into an arena with workers with various colored abdomens.  What they found was that the bluest ones were indeed the most willing to commit suicide. They also found that an extract from these termites was an effective poison capable of killing the attacker not just slowing it down.

There are many other termite species that produce chemicals in their abdomens that can be used in defense though not always through self-sacrifice.  Closer examination of the bluest termite workers reveals that they are likely the oldest workers.  It seems that the blue crystals have built up over their lifetime via production from specific glands in their abdomens that produce the crystals.  Therefore, if they reach old age they become the most effective weapons.

The researchers reasoned that when an old termite workers has worn down its jaws and is an ineffective forager for food, it can’t feed the rest of the termite colony and thus has little use to the colony.  These elderly termites rather than simply leaving the nest to die or be killed by their co-workers, which can happen in some social groups, accumulate a toxin over their life-time and then become willing to sacrifice themselves in defense of the rest of the body.  I say “willing” because the researchers found that workers with less blue abdomens, and thus are probably younger and less toxic, were found to be much less likely to self-sacrifice in the presence of an enemy.  That they do this and there is a benefit to the colony seems apparent, but this behavior might still seem perplexing, not least of which because you may wonder what the origin could be of such a behavior.

An analogy from the human body

One simple way to understand the biology of  social insects is to imagine a colony as a single large multicellular organism in which the individual ants/termites of the colony are akin to the cells of single multicellular organism.   The cells in your body have specific jobs. For example as many as 1 in 10 cells (immune specific cells and epidermal cells) may be involved in defense against foreign invaders or other rogue cells (eg. cancer) of the body.  The other cells transmit electrical signals (nerves), are sensory organs, carry oxygen (red blood cells) etc…   In a colony of termites there are typically workers, soldiers, males and queens.   There may be many specialized workers and soldiers in a colony further subdividing the various duties that must be performed.   Workers typically do the feeding for the colony and then share the food that they have processed with all the other termites that can’t get food for themselves.  Queens obviously are involved in reproduction but they also can alter behavior and developmental by producing hormones that are thought to be passed throughout the colony by the shared feeding. This allows for the communication of signals much like hormones released by cells in an animal body are used to communicate and direct other cells in the body including what type of cell they will become.

One can think of soldiers and these old workers  as the immune system of the termite colony.  Soldiers do not produce food, nor can they participate in reproduction, and they are produced by hormonal influences from the queen.  This is very much like the immune cells of an animal whose sole job is protection of the body even if it means their death.   These exploding workers are just a more dramatic example of an altruistic behavior.  The workers did productive work as a foragers for food and feeders of the rest of the colony but now that they are less effective in old age they become immune “cells” for the whole colony.  You and I have suicide cells called neutrophils. When they encounter possible invasive hosts like bacteria from a puncture wound they self-destruct  to expose the toxic chemicals they had stored in special containers. These chemicals can kill bacteria and any of your cells in the general vicinity.  The result is the destruction of large numbers of cells in a local area.  It is a sloppy, first line of defense in which you not only give up those specific cells but also kill thousands of your “innocent” cells in the death zone for the sake of saving the rest of the organism.  You may witness this cellular destruction in the form of puss that can ooze from an insect bite or other wound.  In short, the good of the many – the whole colony or organism – are more important than the needs of the few or the individual.

These exploding workers are doing something very similar as I am sure that they not only take out the enemy but at times kill some of the other colony members in a form of friendly fire.   The “individuals” of a termite colony or ant colony then are more like cells of single organism. There is no individualism in a colony of social insects just like there is no individualism in a multicellular organism.   A cell of an animal that wishes to do what it wants is actually destroyed by the immune system of an animal because it can be very dangerous for the whole organism to allow individual cells to take on jobs that they aren’t supposed to do. You don’t want your skin cells to try to become brain cells.  The end result of cells that “rebel” against the organism is often cancer – cells that divide indiscriminately inside tissues that normally is under control.   Individuals in a social insect colony that exhibit unexpected behavior or lose their sense of self (all members of a colony produce a chemical that identifies them as being members of that colony) are killed by other members of the colony to protect that colony for the same reasons.

Origins of a toxic defense system

From a theistic perspective how did this capacity for self-sacrifice come to be?  Of course the non-theist should also ask themselves the same question.  Depending on your perspective these diminutive creatures pose different sorts of questions but I believe the most challenging are for the young earth creationists and that is where I will focus my attention.

The literal 6-day creationist is likely to assume that such self-sacrificial behavior would have been impossible, and not necessary,  in a “good” creation which they often refer to as being perfect.  If this behavior was not possible, then were did it come from? The stock answer applied to all such questions is that Adam’s sin brought death and destruction into this world corruption the entire creation not just man.   God, with foreknowledge of Adam’s sin, had designed his creatures with the genetic capacity to develop defensive structures which they would need after Adam corrupted the world.

But how exactly would this particular defensive strategy develop from a “perfect” organism with no need to defend itself? I find the creationists literature of little help here.  In fact, I find it confusing at times.  While appealing to a sovereign God the general explanations make them sound more like deists.  God simply endowed his original creation with gifts and then that programming simply worked itself out after Adam’s fall.   In fact, Dr. Guiluzza, a creation biologists that works for the Institute for Creation Research, denies even natural selections’ role in producing these features of organisms.  He calls the development of new features and new species “programmed filling.”  The very term evokes a deistic view of the world rather than one that God is constantly upholding.   On the other hand, I should point out that Answers in Genesis just yesterday came out strongly in support of natural selection as an agent of change.  I believe that natural selection does play a role in “creating” the toxic capacities of these termites though we would disagree on the details.

I can tell you that the ability to produce and store the toxins in these creatures is no simple single genetic switch – a pre-programmed switch –  that could just be tripped and suddenly these termites had special super powers. The toxic crystals are produced by special glands and stored in special tissues in their abdomen. Those tissues and the crystals don’t appear to have any other use and their development is surely the result of a cascade of many genes and complicated gene regulation mechanisms.  So this ability is not something that any organism is going to suddenly have without acquiring multiple biochemical pathways and organ systems.  The simplest solution for the young earth creationists is to imagine that God simply created these seeming irreducibly complex systems after Adam’s sin to enable the continued existence of termites. But this is typically not an option for YECs because they do not believe God performed de-novo acts of creation after the 6 days of creation since His creation was complete at that point.  Thus the necessity of their appeal to pre-programming during that week of creation.

All of this discussion doesn’t seem to have helped us get any closer to understanding how these exploding termites came to be the way they are today.  It seems reasonable that this line of defense is helpful to the colony that is being invaded, and the loss of older workers is a very reasonable cost of the colony.  However, getting from point A, a standard worker termite with no toxins, to point B, a termite that is a trained assassin, isn’t obvious at first.

Let me suggest the following hypothesis for the above progression.

Let us assume that hundreds of mammals, birds, reptiles and other insects could potentially desire to eat termites as a food source. What could a tiny insect do to dissuade being lunch for so many other animals?  If toxic byproducts of metabolic pathways were stored in sub-cellular organelles this would make the termite less palatable to eat.  As an aside, most termite and ant species produce a wide variety of chemicals that make them unpalatable to most animals as a first line of defense.  A few animals, such as aardvarks and anteaters, have developed resistance to these chemicals with their own special abilities.  Think of them as having counter defenses to the normal typical defenses of ants and termites.

How might termites have obtained these defenses? All cells produce waste products that if not released back into the environment would kill the cell and eventually the organism. This is true of our own cells even if you just consider that each of our cells produced carbon dioxide which we must eventually breath out of bodies.  It seems logical that this would even have been part of the prelapsarian world.

If any variations exist among termite colonies for how much toxin they produce and the termites that produce more toxin might provide more protection of a colony and so the queen will survive.  If she carries the specific version of the genes for that better defense she will pass those genes to the next generation. This is natural selection in action.  New mutations constantly arise and some of the mutations will result in more powerful chemicals that are even more effective at preventing predation and those favorable mutations will be preserved for future generations.  As this continues, toxins in individual cells can’t achieve any higher concentrations (ie. natural selection not longer can affect continued change) but mutations that induce some cells to become specialized for storing toxins at higher rates would provide new features for selection to act upon.  Over countless generations this constant selective pressure caused by the predation, could result in collections of cells whose task it is to store concentrated toxins.  For most species just the production of some toxin confers some advantage to all the individuals in a colony but if some individuals can become more specialized it helps the entire colony. Just like some of our cells are designated solely for the purpose of defense.  Once those members find their role in defenses selection will continue to shape them into more and more effective defenders.

Note that this not a one-step process. This is a long chain of events in which all the termites along that chain are perfectly functional and have responsibilities but those responsibilities and their skills change over time to fit the needs of the whole.  What can appear to be an irreducibly complex set of organs, metabolic reactions and behaviors are, in fact, a built up set of skills each of which served a purpose along the way.

I would imagine that many old earth progressive creationists and young earth creationists would not find this sort of natural selection driven origin of these defensive trait objectionable.  The YECs would claim that no new features are created but the genetic elements were all there in termite originally and natural selection simply helped to sort out combinations of those genetic elements to produce these features.  Likewise the progressive creationists might also claim the same thing. This didn’t change one species from one to another but did alter it traits.

For the progressive creationists who believes the earth is very old time is not a problem and so they may be willing to allow this process to occur over millions of years.  The YEC though only has 6000 years to work with and natural selection for complex trait like this is going to take far longer.  What is often overlooked in the YEC literature is that many characters like toxin production don’t necessarily have a strong selectional advantage.  A small difference in toxins in one colony vs another is only going to have a very weak fitness advantage which means hundreds of thousands of generations may be required to see that difference result in a real change to the species as a whole.  Most characters have weak fitness differences and thus natural selection acts weakly on them.  Most examples that YECs point to in support of natural selection causing rapid genetic change and speciation are to characters with high fitness differences and thus strong selection is occurring.  Take dog breeds, artificial selection is a form of super-strong selection that is rarely achieved in nature.

No matter how this amazing system of defense developed over time, we can agree that social insects are remarkable organisms that continue to astound and amaze as we learn more about them.

Randy J. Guiluzza, “Natural Selection Is Not ‘Nature’s Design Process’,” Acts & Facts 39, no. 4 (2010): 10–11, http://www.icr.org/article/natural-selection-not-natures-design.