The naked mole rat

http://www.youtube.com/watch?v=KDyJfp39XGs (Attenborough – natural history)http://www.youtube.com/watch?v=rGMTj45hW1o&list=PL5B075A61FD958648 (Africa clip – more natural histiory)http://www.youtube.com/watch?v=88iqQ7GkLT0&playnext=1&list=PL5B075A61FD958648&feature=results_video (lab based, featuring a scientist

Ten Reasons Naked Mole rats will inherit the Earth

10. Naked mole rats are the ideal underground organism

Let's start with the basics, shall we? You may have noticed that many of the locations on our list of places to ride out the apocalypse are tunnels, bunkers, and subterranean vaults. Notice a pattern?Come the end of the world, the safest place will likely be underground. Thanks to a variety of physiological neurological adaptations the naked mole rat has evolved to be one very successful subterranean creature, and, by extension, one of the most ideal post-apocalyptic organisms imaginable.

9. Naked mole rats are masterful bomb-shelter buildersNaked mole rats know how to build a good bunker. In fact, these rodents travel exclusively below ground. Individual NMR colonies can range in size anywhere from 20 to 300 individuals, but these populations thrive in vast, intricately organized burrow systems that can cover an area equivalent to twenty football fields. There are specialized subterranean chambers specifically dedicated to rearing offspring, storing food, and eliminating bodily waste — there are even major "highway systems" — complete with on-ramps and off-ramps — that allow for more than one animal to travel quickly over vast underground distances.

    8. Naked mole rats can run backwards as fast as they do forwardsThis might sound like little more than a neat trick, but it's actually a very practical skill — imagine being able to retreat from a threat while still being able to defend yourself. Naked mole rats can do that. And here's what's really cool: this enviable skill is made possible by rows of sensory hairs along their bodies and tails that allow them to "see" while back-pedaling; and said sensory hairs belie another advantageous adaptation:                                                          

                                                                                                                                                                                        

Picture of hairs on body

7. Naked mole rats are "extreme sensory specialists"For example, the somatosensory cortex in a naked mole rat encompasses virtually the entire region of the brain that is usually devoted to vision. This allows the NMR to dedicate more brain power to a variety of other perceptive abilities.

. Barrel patterns and allocation of sensory representations in neocortex. (a,b) Upper panels: sections of flattened cortical tissue from (a) a mouse and (b) naked mole-rat processed for cytochrome oxidase to reveal cortical barrels in layer IV. Rostral is to the left and medial is up. Lower panels: outlines of the individual body part representations within S1. (c,d) A comparison of the size and location of S1 between laboratory rat and naked mole-rat. Note the larger, more medial location of S1 in naked mole-rats as compared with rats. (e,f) The relative sizes of different sensory representations in naked mole-rat S1. (e) Different body parts are illustrated on the basis of their cortical proportions. A naked mole-ratunculus provides a helpful visual aid to demonstrate the extreme cortical magnification of the incisors and head in mole-rat. (f) The percentage of S1 cortex devoted to different body parts.

This nightmarish depiction (also borrowed from the researchers' paper), reflects the percentage of the cortex devoted to a variety of different sensory organs. Good luck finding the eyes.

organs. Good luck finding the eyes.

                                                                                                                                                                                                                                                                

6. A naked mole rat's teeth function like a biological swiss army knifeThe first thing you'll probably notice about the image above is that almost a third of the rodent's somatosensory brain power is devoted to its incisors. As we mentioned earlier, naked mole rats are impressive diggers, but to devote a third of your somatosensory system to digging — and digging only — would be an immense waste of cognitive power. Fortunately, these incisors do more than excavate tunnels. Slow-motion analysis has revealed that mole rats can actually move their lower pair of incisors independently of one another (not unlike a pair of chopsticks). This allows NMRs to interact with one another in a social context, carry and manipulate food and other objects, move and care for their young, and — obviously — feed.

5. Naked Mole Rats are eusocialThe naked mole rat is one of only two known eusocial mammals on Earth (the other, incidentally, is another species of mole rat); in other words: naked mole rats live in colonies, like ants. Each colony is presided over by a single queen who breeds with a few select males. Eusocial creatures are notoriously gifted at operating as a functional unit that is greater than the sum of its parts, foraging for resources, and looking after their own — three great qualities for a species striving to survive in a post-apocalyptic scenario.

Queen mole rats are longer than the rest. The reason is that the hormones during pregnancy, and probably also the physical stresses on their body, induces the lumbar vertebrae to actually grow longer.

Humans, fortunately, do not grow a couple of inches vertically with each child.

4. Naked mole rats know how to use toolsThe naked mole rat's teeth may be ideal for digging, but all that rooting around is bound to stir up some unpleasant, breathable particles. To help keep their respiratory systems clear, NMR's have actually been observed placing wood chips or tuber husks behind their incisors and in front of their lips. Researchers hypothesize that this makeshift face mask helps prevent choking, or the inhalation of foreign material. The NMR's purposeful use of the wood chip during activities that stir fine particulate debris demonstrates its capacity for tool use — a true testament to the species' intelligence and adaptability.

3. Naked mole rats laugh in the face of cancerCancer has never been observed in a naked mole rat, a fact that researchers think may have something to do with a tumor suppressor gene that codes for a protein named p16Ink4a. The p16 protein, like p27 in humans, works by keeping groups of cells (like pre-cancerous growths) in check, and prevents them from proliferating. The difference is that while humans rely predominantly on p27, naked mole rats rely on both. Cell biologist Vera Gorbunova, who identified p16's function in NMRs, described it as "an additional checkpoint" in the body's defense against cancer, which sounds like it would be a pretty handy biological asset in a (potentially nuclear-induced) post-apocalyptic scenario.

Scale bar = 100 micrometers

Contact inhibition at confluence – mole rat cells are inhibited at lower density than rats or humans

Like many animals, including humans, the mole rats have a gene called p27 that prevents cellular overcrowding, but the mole rats use another, earlier defense in gene p16.

Cancer cells tend to find ways around p27, but mole rats have a double barrier that a cell must overcome before it can grow uncontrollably

Telomerase is an enzyme that adds specific DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' ("three prime") end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes.

The telomeres contain condensed DNA material, giving stability to the chromosomes.

The enzyme is a reverse transcriptase that carries its own RNA molecule, which is used as a template when it elongates telomeres, which are shortened after each replication cycle.

Continuous proliferation beyond the Hayflick limit results in progressive telomere attrition and subsequent fusion–bridge–breakage cycles in cells with dysfunctional telomeres. This process culminates in aneuploidy and complex non-reciprocal translocations (NTRs)

2. Naked mole rats are the longest-living rodents on EarthNaked mole rats have been known to live over 30 years — decades longer than is typical of other rodents. The key to NMR-longevity has puzzled scientists for years, but one hypothesis states that it has to do with their ability to shut down their already slow metabolisms when the going gets tough — during times of low food availability

1. The skin of a naked mole rat cannot detect pain — even from an acid burnNaked mole rats lack a neurotransmitter called substance P that in every other mammal helps relay pain signals from the skin to the central nervous system. They also have mutations in a gene that codes for a protein responsible for regulating their ability to sense the pain of an acid burn. Scientists think that NMRs have evolved these mechanisms of pain tolerance to withstand the highly acidic environments of their underground habitats — but the ability to carry on in the face of pain could prove an invaluable asset when the rest of the world is busy falling to pieces.

Spontaneous and histamine-induced scratching in naked mole-rats compared to laboratory mice. A, Mice and naked mole-rats use their back legs to scratch their bodies at a low spontaneous level. The bar graph shows the average number of bouts of scratching observed over 20 minutes (n = 16 mice; 16 naked mole-rats). B, Histamine is not pruritogenic in naked mole-rats. For mice, 10 μg histamine failed to evoke scratching, but higher doses (20 μg - 4.6 mg) evoked pronounced scratching. In contrast, none of the doses tested induced scratching in naked mole-rats

Naked mole rats are unusually tolerant to anoxia and and hypercapnia

Hypoxia experiments on hippocampal brain slices from mice and naked mole-rats. Panel A: A mouse and a naked mole-rat showing similarity of overall size. Panel B: Example data showing response amplitude before, during, and after a 30 min period of hypoxia. Each graph shows data from a mouse slice (open circles) and a naked mole-rat slice (solid circles). he percent oxygen presented during hypoxia is indicated over a line corresponding to when hypoxia was applied.

Suggested question

Naked mole rats show various adaptations to their particular environment. Give an example of (a) a behavioural adaptation, (b) a physiological adaptation, and (c) an anatomical adaptation exhibited by these animals.

Anatomical Large (incisor) teeth for dealing

with tough fibrous plant material and digging

Lack of fur and reduced eyes Physiological eg ability of

neurones to tolerate oxygen deprivation

Behavioural – soldiers defending colony against predators and rivals (instead of running away and saving themselves)

Suggested question

Give two examples of features that help thermoregulation in most mammals that are reduced or absent in Naked Mole rats and explain how each operates to help achieve thermoregulation

Sweat glands ; Secretion of sweat

onto skin removes heat by evaporation;

Reference to latent heat;

Fur; Creates insulating

layer of trapped air;

Suggested question

Give one advantage and one disadvantage in being poikilothermic in comparison to homeothermy.

Advantage – reduced energy consumption;

Disadvantage – metabolic activity will change with change in environmental temperature;

Poikilothermic animals will be less active if environmental temperature falls;

Suggested question

The non-reproductive individuals in eusocial animals do not directly transfer their genes to offspring. In spite of this there must still be a genetic advantage in being eusocial – suggest what this must be.

Non-reproductive naked mole rats share alleles/genes with other members of the colony;

By assisting other members of the colony Queen can produce more offspring;

This increases chances (of the genes they share) being inherited;

Suggested question

What evidence would scientists look for when searching for evidence of heart disease in naked Mole Rats?

Damage to coronary artery;

Presence of atherosclerosis/atheroma (in wall of arteries)

Suggested question

Suggest how extra molecules attaching to proteins might affect their structure and function.

extra molecules) affect bonding that maintains the tertiary structure;

Bonds between R groups are changed/broken;

Ref to named bond eg disulphide, hydrogen, ionic,

Tertiary structure shape is changed;

Suggested question

Suggest what processes would be altered by the cancer causing genes.

Rate of mitosis; Apoptosis

/programmed cell death

Suggested question

Describe the techniques that would be used to insert the cancer causing genes into the cells of rats.

Use of vector; named vector (eg virus/liposome); description of technique of identifying modified cells (eg antibiotic resistance)

Suggested question

How might the immune system of immune compromised mice differ from normal mice.

Any named part of the immune system e.g fewer T helper cells, fewer plasma cells;

Consequence given eg. fewer T helper cells mean less activation of B cells and less antibody production

Suggested question

Name the process by which cells replicate and describe the events that take place in the main events of this process.

Mitosis Stages of the cell

cycle

Suggested question

Explain how transcription factors bring about expression of a gene

Attach to promoter region next to gene;

Allow attachment of RNA polymerase;

Then transcription of the gene begins

Suggested question

Describe the procedures a potential new anti-cancer therapy would have to go through before it could be licenced as a drug.

Animal testing; independent review;

3 stage clinical trials; correct description of

double blind/placebo/ randomisation

Suggested question

Explain how impulses would be transmitted from the pain receptors of a rodent to its central nervous system.

Through sensory neurone; as action potential/ wave of depolarisation/ ; ref to influx of sodium ions into neurone; ref to local currents allowing propagation; ref to salutatory conduction

Suggested question

What is the sequence of neurones impulses would pass through, to result in withdrawing a hand from a hot stove

Sensory neurone to relay neurone to motor neurone;

Via synapses

Suggested question

Describe the responses that humans would show if they were breathing air with 5% Carbon dioxide, and explain how these responses are brought about.

Ventilation rate would increase;

Rise in CO2/fall in pH detected by receptor; receptor identified as aortic/carotid body/medulla; more impulses sent from ventilation centre; to diaphragm /intercostal muscles;

Increased ventilation rate

Suggested question

A brain deprived of oxygen will lead to a brain deprived of ATP/energy. Describe the role of oxygen in the production of ATP.

Final acceptor of hydrogen at end of electron transfer chain; (by removing H) allows proton gradient/chemiosmosis to continue;

without oxygen, Kreb’s cycle and electron transport would cease;

Suggested question

Explain how populations of Naked Mole rats have evolved to be resistant to hypoxia.

Identification of selection pressure is living in a low oxygen environment;

Genetic variability in ability to withstand low oxygen exists in mole rats; due to mutation; mole rats that can withstand low oxygen more likely to survive and reproduce (accept converse); alleles for withstanding hypoxia increase in the population

Suggested question

Use of modern scanning techniques has transformed our understanding of the localisation of function in the brain. Describe how fMRI can be used to study brain function and compare this with early techniques that were used to investigate brain function.

fMRI follows uptake of oxygen in active brain areas; brain activity results in increased demand for oxygen so increase in oxyhaemoglobin; allows researchers to identify regions of the brain involved in particular tasks; early techniques – study of the effect of injury/ animal experiments eg insertion of electrodes/ study of the effect of drugs;

Suggested question

why are the new prosthetics being developed at UCL less likely to damage tissues, and why is there a problem that must be overcome with these prosthetics.

(new prosthetics) are bonded to bone, not pressing on soft tissues; there is a risk of infection entering body between prosthetic and skin;

Suggested question

The queen prevents non-breeders becoming reproductive by altering the hormonal balance in the non-breeders. Compare and contrast the ways in which this kind of communication differs from nervous communication.

Hormonal (accept converse for neural if clearly identified) – slower acting; longer duration; hormone reaches all cells in body but only affects those with receptors; response can be widespread; controls long term changes such as growth;

Suggested question

Describe the techniques and procedures that would be used to produce a DNA fingerprint from a Naked Mole Rat.

DNA extracted from cells; Isolation of gene with restriction enzymes; amplification of microsatellite with PCR; use of electrophoresis; detail of electrophoresis – agarose gel/electric field/ ref to small fragments moving faster/; ref to southern blotting; ref to use of probe; ref to technique of visualising DNA;

Suggested question

Suggest why out-breeding is likely to increase the long term survival of Naked Mole Rat populations.

Increases genetic variation; at least some mole rats will have allele combinations that allow survival in changing environment; prevention of inbreeding depression;

Suggested question

In the suppression of breeding by the queen identify (a) the stimulus (b) the effector and (c) the response for the non-breeding males.

Stimulus is behavioural interaction with queen; effector is testis; response is lowered testosterone/ few and non-motile sperm;

Suggested question

From one ethical viewpoint discuss whether some of the experiments carried out on Naked Mole Rats can be justified.

Utilitarianism; suffering is restricted to few individuals; mole rats have reduced sensitivity to chemical pain therefore have less capacity to suffer; research on mole rats has very large potential benefits to human health;