Tag Archives: centipedes

Prayer

8 Feb

alhazen_b01x

The other day I was asked to tutor a young muslim woman in science by her father, in order that she might achieve her career ambition of becoming a Doctor. A bright young person, she and I discussed the best way to proceed at Tea with Percie my wife’s tea shop on Abbeydale Road in Sheffield. I wanted to understand how I might help her by discovering the way in which she herself learned and understood concepts and, in particular, how she had been taught to date.

It is a very long time since I have done this and I was apprehensive – I did not want to fail them.

I am not a great believer in didacticism, rather, I prefer the Socratic method. Tutor and pupil create a dialogue in which mutual respect allows trust and exchange to develop in order to foster imaginative leaps and insight in the pupil’s mind. It can be a challenging way to teach for both parties: the tutor must be prepared to listen very carefully to a student’s responses, and the student must be encouraged to give precise answers. There is no room for woolly thinking, pat answers, or obfuscation.

There is also no ‘right’ answer in these exchanges, because both parties are moving towards building a model of a (scientific) concept.

Too many of us are happy to be spoon fed by people not qualified to do other than to dispense facts. Thus, the first thing I did was to invite her to check my credentials. It is not a good idea in my book to put any faith in the words of someone who has no form. Googling P.M.H.Littlewood, she discovered the scientific papers I have published on neuroscience, centipede biology, behaviour, neuroanatomy and physiology. I counselled her of the need for skepticism in the pursuit of knowledge together. Her dad, acted as chaperone over a pot of tea. An excellent arrangement for both of us as it made her feel safe. My wife Clare, my psychological chaperone, made me feel safe to use the full extent of my intellect without risking my own ‘fall-out’ (depression usually).

alhazen Al Hazen demonstrating a pin hole camera.

I had given her father some homework for her the previous week when he and I discussed terms. I had asked her to investigate Al Hazen, the 11th Century philosopher who is rightly dubbed the ‘Father of Modern Optics’ from his treatise on light. He was one of the first scholars to pursue what we now think of as the ‘Scientific Method’. My new pupil had identified this achievement and recognised that Al Hazen had also debunked Ptolemy’s ‘Extromission’ theory of vision – that we see by emitting rays, hypothesising and demonstrating by experiment that rays of light enter our eyes (Intromission). I chose Al hazen as a fine example of a polythmath, and a muslim scientist/role model to boot. I thought that my tutee might appreciate this as she is, herself a devout muslim.

I was delighted that she had grasped the opportunity as she told me all about the man who torpedoed Ptolemy. Al Hazen had used practical and thought experiments to postulate that we ‘see’ by receiving light into our eyes, not by beaming light rays out of our heads onto objects. A good philosophical starting point for any student.

I gave her a hand written summary of the ‘scientific method’ on a scrap of paper as a reward, and we proceeded to split light with a prism. She immediately pulled out her note book to write.

I said “Please put it away, it will only hinder you, you can make notes in your own time if it helps” – I wanted her to exercise her young brain to make its own connections and memories unfettered by slavish wrote recording.

As we progressed more deeply into discussing the nature of light she said “I don’t really like how all these subjects are separate, they don’t seem to be connected” showing me a glossy science revision text book. “Well, everything is connected”, I said, “but it is easier for teachers to dole science lessons out in spoonfuls when faced with a large class of students – who are not really interested. What bit of science do you particularly not get?”

“Chemistry” she said “bonding in particular”

“To ‘get’ this you need a model” I said “Because it is impossible to see, unlike the rainbow exiting the prism, which gave us a clue to the make up of white light”

“If you think of the atoms of a metal, all lined up like the congregation of the mosque, all facing Mecca and the Imam, then the prayers of the Imam are the electrons that hold the people (atoms) together” I suggested.

Electrons as prayer from the Imam, she loved this. Her dad had initially bridled when I mentioned the Mosque, but he liked it too.

“I’m sure you could think of your own analogy to describe when electrons are shared – as in covalent bonding, or where atoms with opposites charges stick together as in ionic bonding?

I chucked a sugar cube into water and some salt to get her thinking. “Food for thought, and to help you – have a fresh look at the periodic table – Mendeleev has given you a rather elegant menu of ‘stuff’, which we might consider in the light of what you have now discovered…”

Arabic teaching, learning and literature is vast and underpins many ‘Western’ concepts. Muslim tradition places great emphasis on logic, writing and memory – but imagery is eschewed in their teaching. Western learning is riddled with visual analogy based upon natural forms. I believe that powerful understanding can emerge in the exchange. Perhaps in these troubled times our prayer should be to seek the understanding of our children.

أول الشجرة بذرة
“A tree begins with a seed.”

Thigmotaxis

1 Jan

Centipedes, like many other small creatures exhibit a curious behaviour called thigmotaxis – they like to squash themselves into corners in order to maximise body contact with surfaces.

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This is a common brown centipede resting against the side of a plastic sandwich box.

The reason small soil dwelling creatures do this is because they are particularly vulnerable to changes in humidity, they dry out quickly, or become water logged. The behaviour is so overwhelming that it can mask other reactions to external stimuli such as vibration, chemicals, etc..

Years ago I spent long hours studying the behaviour of Lithobius forficatus L. (the common brown centipede) as a Ph.D. student in order to discover what the beautiful structures on its hind legs were for:

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This is a diagram of the underside of a male centipede. You can see that the fattest segments of the last four pairs of legs, closest to the body, are equipped with a row of interesting pores. These are the coxal pores. Under the pores lies a curious tissue, known as the coxal organ.

You can see the pores more clearly here:

Coxal pores dimensions

At very high magnification the organ looks like this:

LM coxal pores

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Under the electron microscope the cells look for all the world like ‘kidney’ or ‘malpighian tubule’ (insect kidney) cells. On this basis it was classified as a ‘typical transporting epithelium’, a not very helpful description as we had not a clue what might be transported.

The Behavioural experiments proved compelling and, using a circular choice chamber to get around the centipede’s natural tendency to flatten itself to a wall I was able to demonstrate that the coxal pores were responsible for releasing a sex hormone, or pheromone attractive to members of the opposite sex.

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I came to the conclusion that the main problem facing centipedes (and anyone living under ground) was not drying out, but becoming water logged. So the coxal organ is most probably very good at getting rid of excess water (centipedes living in xeric or dry habitats have very small coxal pores, or none at all), and in so doing chucking out a useful ‘come on’ signal to other centipedes of the same species. The pheromone chemistry is phenolic and related to the chemistry of centipede cuticle (hardly surprising given that the coxal organ is modified cuticular epithelium which normally secretes the centipedes exoskeleton).

Sticking closely to a surface is not my thing. I prefer to venture out and discover things anew. Multifunctionality is common amongst amongst biological systems – it is the stuff of evolution and natural selection: a hand becomes a wing (pterosaur, bird, bat); a wing becomes a diving tank (Great Diving Beetle’s plastron); a zoologist become a woodworker…… A close study of centipede backsides was instructive in beginning a small voyage of discovery for me, a gift by a true mentor J.Gordon Blower, the ecologist and millipede man who pointed them out to me whilst smoking a number 6 filter tipped in his nicotine stained lab way back in 1979.

JG Blower 1

I have always thought the phrase ‘there is no need to re-invent the wheel’ the dullest of aphorisms. Re-invention is human, discovery and rediscovery a divine gift. Get out there and look at something very small, or something very big, but please do go and look, because your discoveries will be unique.

PMH Littlewood. Fine structure and function of the coxal glands of lithobiomorph centipedes: Lithobius forficatus and L. crassipes (Chilopoda, Lithobiidae) 1983. J. Morphology  Vol 177

PMH Littlewood. The chemosensory behaviour of Lithobius forficatus. 1. Evidence for a pheromone released by the coxal organs (Myriapoda: Chilopoda).Journal of Zoology Vol 211 January 1987

PMH Littlewood and JG Blower. The chemosensory behaviour of Lithobius forficatus. 1. Evidence for a pheromone released by the coxal organs (Myriapoda: Chilopoda).Journal of Zoology, Vol 211, 1987

PMH Littlewood.The water relations of Lithobius forficatus and the role of the coxal organs (Myriapoda: Chilopoda).J.Zoology, Vol  223, 1991