The naked mole rat (Heterocephalus glaber) is found in the dry, tropical grasslands that cover Kenya, Ethiopia and Somalia and has a rather unsightly appearance shaped by the conditions to which is has adapted. They are small rodents with a body length around 8-10cm and their body mass lying somewhere between 25-70 grams; are completely hairless, wrinkled and pale-skinned. Their diet consists mainly of the underground parts of plants, (particularly tubers that are formed by many plants that grow in the arid deserts of East Africa. Like many animals in similar climates they obtain all the water they need through their food and therefore do not drink.

As its name suggests, the naked mole rat resides in deep, underground burrows like moles and indeed, due to their dark habitat, they are completely blind but these are where the similarities end. Their acute sense of hearing and smell compensate for their lack of sight, allowing them to sense vibrations through the dense earth and assess each other’s status by smell. Rather than digging with large burrowing hands, the naked mole rat uses its elongated teeth like a shovel to scrape away earth and shape the extensive tunnels of the den, which when stretched out can reach up to two or three miles in length. In order to keep the dirt out of their mouths when they dig the lips of the naked mole rats close behind their front teeth, which remain permanently exposed, adding to their already rather grisly appearance.

Appearance aside, their oddities are abundant:

Like some other rodents (such as rabbits, chinchillas and hamsters), the naked mole rat practices coprophagy (or the eating of faeces). Like other rodents who eat their own faeces in order to acquire a higher intake of Vitamin B12 (crucial for maintaining a normal functioning of the brain and nervous system and the formation of blood), the naked mole rat has great difficulty in properly digesting tubers and plants due to the high cellulose content. The re-ingestation of faeces (usually their own, or, if they are pups these are provided by other male workers) provides the mole-rat with gut fauna (bacteria), which helps to break down the cellulose and maximise the nutrient uptake during the digestion process.

At school your biology teacher probably gave you the following criteria for defining mammals; give birth to live young, produce milk from glands, and are warm blooded. And your biology teacher would be right…well, almost. Naked mole rats are mammals, but unlike other mammals they are unable to thermoregulate (use their metabolism to maintain a steady body temperature) meaning that they are essentially cold-blooded. Like reptiles, their core temperature fluctuates with the ambient temperature, so to control it they huddle in large groups to slow the loss of body heat when cold or alternatively bask in shallower surface tunnels, which are heated by the sun. When temperatures get too hot they merely retreat deeper into the burrow where it’s cooler.

The naked mole rat is also one of the hardiest and most resilient animals you’ll ever likely meet. Due to the lack of the neurotransmitter Substance-P (responsible for transmitting information regarding tissue damage to the central nervous system), the mole rat startlingly has no skin sensation and is unable to feel pain! It is also one of the only mammals in which cancer has never been observed.

Cancer is caused by a cell or group of cells, which either multiplies beyond normal limits (uncontrolled growth), or intrudes on and destroys neighbouring tissue. The mechanism that checks cancer is a gene called p16 (a tumour suppressing protein), which stops the formation of new cells once a group of cells reaches a certain size. Most mammals have another gene called p27 (a cell-cycle inhibitor protein), which does a similar task, but prevents cellular division at a much later point than p16. The existence of both p16 and p27 genes in naked mole rats creates a double barrier that prevents the development and spread of cancer cells. To top this off, they are the longest living rodent in the world. While most rodents have an average lifespan of 2-5 years, the naked mole rat has been found to live up to 27 year in captivity.

But perhaps what makes the naked mole rat particularly unique is that they are the only known mammals (with the exception of their closely-related cousin, the Damaraland Mole Rat) that live in eusocial societies. Eusociality (or true sociality) is a social state that is defined by scientists in biology as the existence of reproductive altruism and kin selection (strategies in evolution that favour the reproductive success of an organism’s relatives, even at a cost to their own survival and/or reproduction). This contains the following criteria:

1. Reproductive division of labour (with or without sterile caste systems)
2. Overlapping generations
3. Cooperative care of young

While many other mammals’ exhibit one or two of these aspects, only the naked mole rat truly exercises all three traits. Whereas mammals like great apes, large cats and horned or antlered animals like the deer and moose all have the ability to reproduce and are equipped to fight for their right to mate in order to ensure the survival of their individual genes, the naked mole rats sacrifice their own genetic preservations for the good of the colony, resulting in a truly altruistic (self-sacrificing) society.

A female, a queen, will mate with perhaps three or so dominant male rats and will give birth to the entire population of the colony, which can surpass as many as 100 individuals at a time. This breeding system is most closely characterized as polyandry (one female with many male mates) since the queen will copulate with multiple breeding males. Males generally follow an age and size-related hierarchy whereby the oldest and biggest males enjoy breeding rights with the queen. Interestingly enough, when a female becomes a queen she actually grows longer by increasing the distance between the vertebrae in her spine! With a gestation period of around 70 days, the queen can produce a litter every 80 days, 5 litters a year and may produce up to 50 litters in her lifetime (as many as 600 pups). She will not be replaced until her death when the next female in line develops hormones and behaviours similar to the queen. She will then aggressively fight with several other females for her place as queen. Her children (the workers), both male and female, although physiologically able to reproduce, will remain sterile throughout their entire lives in order to carry out duties such as burrowing, searching for food (tubers, roots and seeds) and raising the young in order to ensure the survival of the colony. This refusal to reproduce is known in nature as reproductive suppression. This type of societal structure is most commonly found in the colonies of social insects such as ants, bees, and wasps as well as termites, all with reproductive queens and more or less sterile workers and/or soldiers, but the naked mole rat is the only known mammal to have evolved in this way.

Now, reproductive specialization is found in various organisms in nature and generally involves the production of sterile members of the species, which carry out specialized tasks and care for the actively reproductive members. This can be manifested by the modification of behaviour (and also in the case of many insects, anatomy) of individuals within a group for security and preservation, including self-sacrifice.  Eusociality with biologically sterile individuals characterizes the most extreme form of kin selection in the natural kingdom. But if individuals are not striving to pass on their individual genes, why and how is this form of society effective in terms of natural selection? What’s in it for the naked mole rat? In a world in which every individual competes and strives to outdo one another to pass on his/her genes, why has naked mole rats evolved to be a passive, sterile and altruistic species and why have they been successful?

Well, presumably, the evolution of the mole rat’s kin selection is tied to the subterranean habitiat: by closing the top of their burrow the mole rat’s ancestors found that they could escape some of the dangers of surface predators such as snakes, which often find their ways down burrow entrances.  This enclosed habitat consequently led to inbreeding which produced individuals with high genetic similarity and an environment that found kin selection to be more beneficial than individuality in the colony. All social animals must modify or restrain their behaviour in some way in order to cultivate a harmonious environment when living in a community but what we have here is an extreme form; a society in which every member of the colony is related. They are a family; all of them brothers and sister and sons and daughters and therefore their genetic pool is closed and contained. They have no reproductive competition from the outside; no sexual selection pressures. With a rodent’s resilience to the more common genetic flaws that often occur from inbreeding in other types of mammals, the naked mole rat has found a niche in establishment of a unique kind of mammalian society but one with traits that can be seen in the groupings of apes, human societies and even economic theory; one where ‘altruism’ can cement relationships to ensure both personal and genetic continuity and security. In other words ‘what is good for the colony is good for the individual.’ Could it be that what we are seeing in the societies of the naked mole rats is a remnant; a glimpse into the early evolutionary developments of selflessness and, by extension, perhaps even morality? I’ll have to do more research…

Creationists are always trying to catch scientists out. Whether it is supposed gaps in the fossil record or our present lack of understanding regarding the origins of the universe, the religious right are quick and eager to fill every unknown that scientists are working on with the words ‘God’ and ‘design’ as alternative ‘explanations’. Darwin’s Theory of Evolution comes under attack perhaps more than any other scientific theory due to the direct contradiction between the biblical creation myths (Adam and Eve and the Fall of Man) and the overwhelming evidence that our species share a common ancestry with the other great apes: chimps, orang-utans and gorillas. The hard evidence that scientists have provided over the years is often met with incredulity and phrases like “maybe your ancestors came from monkeys, but not mine!” It should not be taken as an insult nor should it be embarrassing to acknowledge that we are descended from ancient apes (indeed we are apes). On the contrary, we should take great delight in the fact that we are intimately connected by our DNA (no matter how distant the connection may be) with every other living creature on Earth. A decade ago, the fruit fly (Drosophila melanogaster) was the second creature to have its entire genome (a complete genetic blueprint with all the information an organism needs to construct itself) mapped out. Astonishingly, according to research carried out by scientists, about 75% of known human disease genes have a recognizable match in the genetic makeup of fruit flies, and 50% of fly protein sequences have mammalian analogues (biological structures). What this means is that you share a hell of a lot of genetic information with an insect no bigger than a fingernail clipping!

People who are not scientifically literate (and even some that are, though these are few and far between) tend to point towards Intelligent Design as an alternative theory that better describes how certain features of the universe and living organisms came to be and that the results of what we see are guided by a creator and not due to the ‘undirected’ processes of Natural Selection. In evolutionary biology, creationists claim that the various components needed to make complex systems (such as an eye or brain) function correctly could not have evolved gradually over long periods of time; claiming that these separate components provide no benefit by themselves and thus entire systems must have been miraculously designed and created together at the same time. This particular argument that constitutes part of the Intelligent Design theory is known as Irreducible Complexity and proponents of this theory jibe biologists with such redundant questions as ‘what’s the use of only half an eye?’ Well, let’s ask the starfish: on the end of each arm there is a tiny, simple eye (ocellus), which has a single lens that collects and focuses light onto the retina allowing the starfish to only differentiate between light and dark. Although unable to make out shapes or colour, this primitive eye is useful for sensing movement, enabling the starfish to detect both potential prey and predators. Things that develop in slow steps can lead to increasingly complex systems, though some are easier to explain than others. One champion of creationists is the Bombardier beetle.

The Bombardier beetle (in the large family Carabidae) is the generic name for a type of ground beetle covering 5 separate tribes and over 500 separate species. Like other insects these beetles have developed tools to protect themselves from predators, but it is the incredibly complex way in which they do this that has brought them into the evolutionary spotlight and has led them to be praised by creationists as ‘evidence’ of Irreducible Complexity. When disturbed, the beetle sprays a boiling chemical solution from special glands in its abdomen into the face of its predator. The solution is created from a mixture of two reactant chemical compounds – hydroquinone and hydrogen peroxide – which are mixed together and explode in the face of their enemies. Creationists claim that any alteration in the delicate chemical balance of these two chemicals would lead to catastrophic consequences for the bombardier beetle and therefore, this extraordinarily complex defence mechanism could not possibly have gradually arisen by a step-by-step process as stated by evolution.

Well, before we jump to any conclusions let us take a closer look at the science behind this mechanism:

The two reactive chemicals – hydroquinone and hydrogen peroxide – are secreted through glands and are stored in two separate chambers found in the rear tip of the beetle’s abdomen. When attacked by a predator, the beetle contracts its muscles, forcing the two chemicals into a mixing chamber or reservoir containing water and catalytic enzymes (peroxidase), which are secreted through cells that line the walls of the chamber. When combined, these enzymes break down the hydrogen peroxide to form oxygen and water and catalyze the oxidation process of the hydroquinones, turning them into p-quinones (quinones are an organic compound formed from aromatic – ‘a chemical compound that has a flavour or odour’ – compounds such as benzene – a highly flammable liquid). This chemical break down forms free oxygen which generates enough heat to rapidly bring the solution to boiling temperatures that can surpass 100°C. As the liquid solution reaches boiling point about a fifth of it evaporates into a gas. This gas increases the pressure in the chamber, which builds up and forces the entry valves from the separate storage chambers to close, protecting the beetle’s internal organs. The pressure then forces the boiling solution through a small outlet valve and into the atmosphere with a loud popping sound caused by flash evaporation (when vapour or steam undergoes a reduction in pressure change when passed through a valve into a less pressurised environment). The bombardier beetle is able to discharge this solution about 70 times in rapid pulses that last no more than a second and can be fatal to attacking insects and spiders and, due to the temperature of the liquid, can be very painful to humans. Remarkably, the openings of some bombardier beetles (for example the African variety) have also developed nozzles at the end of their abdomens that can swivel through 270° and are able to aim at predators and be fired with considerable accuracy in many directions.

So how did this all come about? Though it all seems rather complicated, we can break it down and look at how these intricate mechanisms can (and do) develop on a gradual, step-by-step basis.  Just to recap; creationists claim that the reactant chemicals are so sensitive that any imbalance would lead to catastrophic end for the beetle meaning that this process could not have possibly arisen from a gradual evolutionary process, but must have all been ‘created’ at the same time.

There are three problems to the creationists claim, mainly:

1)      Hydroquinone and hydrogen peroxide do not actually react when mixed together unless a catalyst is added (in this case an enzyme secreted from cells that line the mixing chamber inside the beetle). In other words, any amount of these two chemicals is completely harmless to the beetle or any other insects unless a catalyst is added and therefore there is no ‘delicate’ chemical balance.

2)      The quinones are not unique to the bombardier beetle and are indeed found in most other insects and invertebrates. They are produced by cells, which harden the skin into a cuticle or exoskeleton along with an unpleasant taste making an effective deterrent to predators.

3)      The strength of the chemical reaction relies on the concentration of the hydrogen peroxide. The higher the concentration, the higher the amount of oxidization, which results in a more violent reaction.

All of these issues can easily be explained from an evolutionary perspective: As stated above, the quinones are commonly found in many insects and are produced in tiny indentations or small glands in the ‘skins’ of invertebrates. Due to the unpleasant taste, some beetles and insects have developed muscles that can contract around these glands giving them the ability to secrete larger quantities of quinones on demand in order to deter predators when they attack. The bigger these indentations, the more quinones they are able to secrete, thus making the survival rate amongst beetles with larger quinone sacs higher than those with smaller ones. Over time it is possible for these sacs to grow and develop into larger ducts which we find in the abdomen of bombardier beetles today. When predators’ resistance to these chemicals develops (see evolutionary arms race*), other quinones (such as hydroquinone) then develop. This is later mixed in with hydrogen peroxide (a common by-product of cell metabolism*)

*Cell metabolism is a set of chemical reactions that happen in cells that use energy to construct cellular components such as proteins (which form enzymes) and nucleic acids, which allow them to grow, reproduce, and maintain their structures. These chemical reactions are organized so that one chemical is transformed into another through a series of steps by a sequence of enzymes. Enzymes act as catalysts and allow these reactions to be carried out quickly and efficiently.

After mixing, these two chemicals then react with enzymes and generate heat and pressure, which produce a more reactive substance and therefore a more efficient deterrent against predators. The hydroquinone doesn’t actually need to be there at all for the explosive defence mechanism to work – the hydrogen peroxide would be quite enough – though its presence does enable a faster reaction to take place. As the enzymes break down the hydrogen peroxide into a reactive substance, they also break down the hydroquinone, which releases more oxygen, helping to fuel and speed up the reaction between the enzymes and the hydrogen peroxide, and make for a more violent chemical reaction. The real key lies in the concentration of hydrogen peroxide, which can (and best) be explained by a gradual increase over time. A lower concentration would cause a gentler reaction (with a mild temperature), which may be enough to deter an attacker (though perhaps not damage or kill it) and would also be relatively harmless to the bombardier beetle. Natural selection would favour those beetles whose solution was more effective at deterring predators, leading to a gradual shift toward a higher concentration of hydrogen peroxide and ultimately more violent reactions as well as an increase in the beetle’s own resilience to the powerful solution (perhaps due to the same increase in quinones that harden the beetles exoskeleton).

The bombardier beetle is a wonderful example of how evolutionary processes can span millennia to form extremely complex and seemingly impossible organisms through small, gradual changes and it is through the wonder of modern biological science and chemistry that we are able to understand how these changes occur.

Complexity cannot and does not occur instantaneously. You cannot throw a pile of junk metal into the air and expect it to land in the shape of a working car, which is the approach that creationists and the religious right seem to take. Darwin’s Theory of Evolution by Natural Selection is the only logical, methodical and elegant explanation we have that is able to explain the huge diversity of the natural world and all its wonders. We should not feel belittled or humiliated in accepting that our origins lie with the great apes and other mammals, with reptiles, birds, fish, insects and bacteria, but instead should find both solace and a sense of wonder. It has taken trillions of births, lives and deaths over the 3.5 billion year history of life on this Earth for us to be here. We are a lucky few indeed.

In the concluding words of that masterpiece of scientific writing from great man himself: ‘There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.’

As the name suggests, this largely aquatic-dwelling amphibian is found throughout the Iberian Peninsula (Portugal, Spain, Andorra and Gibraltar) and Morocco. They can grow to up to 30 centimetres (12”) in length and feed mainly on small insects, worms and tadpoles. The ribbed newt was relatively common and, preferring calm, stagnant water could be frequently found inhabiting ponds and old village wells. However, recently the IUCN (International Union for Conservation of Nature) designated the species as being ‘Near Threatened’ in 2006 due to an apparent dwindling in population caused by damage to their aquatic habitat from such things as drainage, chemical pollution and development caused by demands in tourism, making the species now largely extinct in coastal areas and around large cities.

Being small, soft and numerous (frogs eggs can number in the thousands), and lacking in claws, teeth, and strength, amphibians form an important part of the food chain and are hunted by mammals, birds, reptiles and even some arthropods such as spiders. Despite this, many amphibians have developed powerful toxins in order to deter attackers, such as the ‘Poison Dart Frog’ – named due to the Amazonian Indians’ habit of tipping the ends of their hunting darts with the frog’s poison. The poison is produced from a gland (the parotoid gland) and secreted through pores in the skin as a milky alkaloid (a chemical bond formed by base nitrogen atoms with an alkaline pH). The downside of this defensive tactic is that in order for the poison to be administered to the attacker the amphibian must first be bitten, which could result in serious injury or even death for our froggy friend. It is for this reason that many frogs, toads, newts and salamanders have evolved bright colours and patters (an evolutionary mechanism known as aposematism) to warn predators of their toxins without the need of being bitten first! However, being dull gray in colour it seems that the Iberian ribbed newt didn’t get the memo and instead of following this rather sensible pattern, devised its own way of dealing with its predatory problems. Although it secretes poison through its skin like other amphibians, it has a unique and grim way of administering the dose: It punctures its own skin with its sharp ribcage, which, after tipping themselves with poison upon exiting the body, are left protruding to stab or graze any unlucky attacker. The combination of poison and spikes makes a very effective form of defence (especially if the newt is picked up in the mouth of its predator) and this is how she does it:

Imagine looking down at the skeleton of a newt from above with the backbone running vertically from north to south in front of you. In its relaxed state the sharp, spear-shaped ribs of the newt gently flow back at an angle (averaging around 50°) from the spine toward the tail like waves streaming behind a slow moving ship.  However, when agitated, the newt, whilst keeping the rest of its body still, rotates its entire ribcage anteriorly forward so that the ribs angle perpendicularly to the spine at an angle close to 90°. This massive forward movement of the ribcage causes the body to expand so that the sharp tips of the ribs lacerate the body wall and project freely from the sides of the trunk forming a row of –now poisonous– barbs.  Light microscopy illuminates the complex anatomy of the animal, and shows that each spear-like rib is connected to its corresponding vertebra (individual columns that make up the spine) by a well-developed, flexible, two-headed joint.

This incredible (albeit rather gruesome) form of defence was first noted by a natural historian 1879 and it was previously thought that the newt must possess some permanent openings or pores through which the ribs could pierce. Indeed the newt does have a row of tubercles (wart-like nodules) running down either side of its trunk and it is through these that the ribs seem to project. However research has shown that although these tubercles exist, the skin in the penetration areas are completely firm and lack any permanent pores through which the ribs could be projected. The newt has to therefore pierce its own skin de novo with every time it adopts a defensive posture.

Despite this masochistic action, the laceration seems to do very little (if any) harm to the newt and the animal has been observed to resume such normal activities as eating and mating almost immediately afterward. Amphibians’ poison is usually contained to the glands, though despite the poison-tipped ribs being contracted back into the body leaving the substance to seep into the body tissues, the chemical seems to have no effect on the newt at all, leading scientists to conclude that its system has developed a complete tolerance to the poison. The self-inflicted wounds also cause very little harm due to the noted rapid healing processes of amphibians, which are known not only to have an extraordinary ability to repair their skin but can also regenerate limbs, eyes, spinal cords, hearts, intestines, and even their upper and lower jaws.

*This is due to a biological process known as cell dedifferentiation. In biology cell differentiation is the process by which a less specialized cell (i.e. a stem cell) transforms itself into a more specialized cell type (a cell that serves a specific purpose e.g. a blood cell/bone cell etc) in order to carry out a specific job within the body. Dedifferentiation is a similar process but it works in reverse; where differentiated cells (cells that already serve a specific purpose) revert to their earlier developmental stem-cell stage, often as part of a regenerative process. The cells at the site of the newt’s (or other amphibians’) injury have the ability to de-differentiate, reproduce rapidly, and differentiate again to create new skin, a new limb or even a new organ and provide rapid rehabilitation.

The Iberian Ribbed Newt is a wonderful example of how if any kind of genetic variation (no matter how bizarre) proves to be at all beneficial to the survival of a species, natural selection will see it thrive and multiply.

The shrimp locks its claw into place as one would pull back the trigger on a gun to prepare to fire. Then, using the intensely powerful muscles in its grotesquely enlarged claw, the shrimp snaps its claw shut with such a force as to create a shockwave through the water. The pistol shrimp not only uses these snaps as a form of communication with other shrimp, but these shockwaves are so powerful that they can stun or even kill other shrimp or small fish from a distance of up to 4cm away! The shrimp literarily uses it’s ‘pistol’ for hunting!

So how does it do this?

Well, it’s actually all to do with sound. Although the pistol shrimp’s maximum length may not even exceed your little finger, the cacophony of sound that it creates by snapping shut its claw can reach an astounding 240 decibels (a sound pressure almost twice that of a jet engine from 30 meters away!) and due to the acoustic properties of water (sound waves travel through a liquid much more effectively than through the air) can be heard from over a mile away and can even interfere with submarine transmissions. Originally these clicks were thought to be nothing more than the sound of either pincer slamming together at great speeds, but research carried out by both the University of Twente in the Netherlands and the Technical University of Munich discovered something much more interesting: the snap is actually caused by the collapsing cavitation bubble (or bubble implosion) caused by the sudden (the snap lasts no more than a millisecond) increase of immense pressure exerted by the claw as it squeezes together.

*(Here’s a quick basic physics lesson on pressure for you: suppose you have a cylinder full of atoms and a piston pushing down from above. As the piston moves down the atoms are compressed into a smaller space. What happens when an atom hits the moving piston? It picks up speed from the collision as would a stationary ping-pong ball should you hit it with a paddle. This increase in movement (kinetic energy) gets more frequent as more pressure is applied (just as a ping-pong ball would bounce more frequently should you hit it in a smaller space than in a larger one), and so all the atoms in the cylinder will pick up speed and so get ‘hotter’. This is all heat is: the kinetic energy (movement/excited state) of atoms. This means that when we compress gas, the temperature of the gas increases and this is exactly what we see here with the pistol shrimp. When the shrimp’s claw snaps shut, it does so at such a rate that the bubbles of air in the water are compressed as energetic liquid is forced into very small volumes.)

This collapse of the cavitation bubble creates spots of high temperature that emit shock waves, which are the source of noise. However the most incredible part is that the snap can also produce sonoluminescence (light created from the implosion of bubbles in a liquid when excited by sound). As it collapses, the intense pressure means that the interior of the bubble momentarily reaches temperatures of over 5,000 Kelvin (or 4,700 °C). To give you some idea of just how hot that is, the surface temperature of the sun is estimated to be around 5,800 K (5,500 °C)! This was the first observation by a scientist of this type of light production by any animal in nature (although it has subsequently been discovered that the Mantis Shrimp – a close relative to shrimp, but not actually a shrimp at all – is also capable of creating sonoluminescence in a similar fashion, though with a different set of tools).

It has also been discovered that pistol shrimp have the ability to reverse claws. When the snapping claw is lost for whatever reason, the missing limb will regenerate into a smaller claw and the original small claw will grow into a brand new snapping claw, capable of producing the same devastating effect as the lost ‘pistol’.

So if you ever go diving and encounter a pistol shrimp, you’ve got to ask yourself one question: “Do I feel lucky?” Well, do ya, punk?