“You live 6 weeks and I live 6 months”

Says the winter bee to the summer bee

I suppose the Nobel prize winner Bob Dylan did not think of the honey bee, when he penned the lyrics to his song “Forever Young”, but when we compare the longevities between summer and winter honey bees, it almost seems as if the long-lived winter bees stay forever young: they stay around from about October until at least March while the short-lived summer bees are lucky to reach an age of 6 weeks. The reason is not that during the summer, bees are more susceptible to disease, preyed upon more heavily or work so much harder than the winter bees, for even though winter bees spend the entire winter in the hive, they too work hard. They shiver to create heat and make sure that the cluster of bees surviving the cold season with their queen does not become colder than 15°C. But how can they possibly stay active (and alive) for so many months longer than the summer bees?

First of all, the members of a bee hive need to sense that the cold season is approaching. This may involve the increasingly difficult task of finding pollen in August to feed the brood. It follows that brood rearing becomes reduced and eventually stops until it resumes in January. With no foraging summer bees needed, they all die in the autumn and are replaced by the morphologically identical winter bees. The latter begin to store large amounts of ‘vitellogenin’, (a glycolipoprotein known to be a zinc carrier) in their fat body, the equivalent of our liver. In the winter this substance also increases in the haemolymph, the equivalent of our blood.  At the same time, the so-called ‘juvenile hormone’, important during the nursing of the brood, decreases to almost undetectable levels. The amount of a neuromodulator molecule from the brain, known as octopamine, also falls when foraging is no more possible in winter.

The nutrients stored by the winter bees in the form of vitellogenin are not used by them for themselves, but are kept to be utilised when new bee brood is produced again by the queen bee in anticipation of the coming spring with its flowers and sources of protein-rich pollen. How the queen bee ‘knows’ that spring will approach when she starts to lay eggs anew in the middle of winter, the coldest and darkest season of the year, is still a mystery, but how the winter bees keep themselves and their queen warm is much better understood. In the ball-like cluster that the winter bees form, those at the periphery every now and then exchange places with bees from the warmer centre and then also to replenish their food intake. After all, to create heat by shivering, means that they are expending a lot of energy.

The ‘fuel’ the bees use to warm themselves and the hive up is sugar!  It’s the main or perhaps the only reason why they collected nectar and turned it into honey during the summer: the carbohydrates keep them alive throughout the winter, so that in spring they can feed the new brood with the vitellogenin they stored in their fat body. Actually, rearing new brood already starts in late winter when pollen are not yet available and the trigger for the transition from winter to short-lived summer bees is, therefore, not at all understood. Perhaps the decrease in vitellogenin, needed to feed the new brood, causes a concomitant rise in juvenile hormone and octopamine. The fact is that all winter bees, irrespective as to when they left their pupal cases, whether that was in October and the early months in winter or as late as January, they all die within a very short time. Forever young? Well maybe not forever, but applied to humans it would be a life of 400 years! And if that’s not long enough, how about the rotifer, a tiny wheel animalcule, an extreme “Rip Van Winkle” of the animal world? Dormant in a frozen state for 24,000 years, it was revived recently by the Russian soil scientists Lyubov Shmakova and colleagues of Pushchino in Russia, and it even multiplied (it did not need a male). A multicellular organism with a gut, a nervous system, sense organs, frozen stiff, for 24,000 years: what a life –  if you can call that a life at all.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

A Bit of Philosophy on Movement, Motion, and the “Mirror Neurons”

One of my graduate students’ fathers was a Professor of Philosophy and in most Anglo-Saxon countries a doctorate, obtained in whatever subject it may be, is usually called a PhD (which stands for Doctor of Philosophy). You might call this a quirk of history, going back to antiquity when Greek mathematicians, scientists, healers and thinkers were all “philosophers”. Anyway, if you hope a conversation with a philosopher will help you find answers to questions you carry in your mind, you are likely to be in for a disappointment and may leave the philosopher with more questions in your mind than you had before. Perhaps that is the function of philosophy: to make you question what is real and what isn’t and to make you think what makes “you” to be “you”. Bonjour Monsieur René Descartes: Cogito ergo sum!

Anyway, my conversation with a philosopher dealt with movement and motion, which I thought was the straightforward action of something being in the process of changing its position from one place to another. But that assumes, so the philosopher, that a moving object occupies successive positions ever so briefly while it is moving. But it is impossible to ‘count’ such positions as there would be infinitely many. It’s not like an old movie, in which separate pictures in quick succession create ’movement’. If I’d argue that one could say an object decreases its distance from one place to another while “on the move”, the philosopher would argue that a moving object has no definitive starting point. Moreover he’d point out that while the Earth rotates, we all move all the time and he made me think of sitting in a moving train watching a fly flying from one seat to another. Motion is indeed “philosophy”!

However, biologically motion and rest, we agreed, are different modes of a moved body, but to visibly move a part of the body, muscle fibres need to be activated to contract by signals from a nerve cell: a neuron. Now imagine you wave to someone you don’t know, what happens? Most likely that person will wave back. A child, playing happily, upon observing another unrelated child cry is very likely to begin to cry too and attendants of a meeting in which the speaker repeatedly touches his ear may also begin to touch their ears. This copycat phenomenon is due to so-called ‘mirror neurons’ in the brain that were discovered by Di Pellegrino et al. and Rizzolatti in 1992. The mirror neuron system has evolved at seemingly different rates in and among species and involves hand and mouth visuo-motor and audio-vocal mirror neurons in different regions of the brain (more precisely for those who want to know: the superior temporal sulcus, the pre-motor cortex, the inferior parietal lobe). Interestingly, neurons of the premotor cortex apparently distinguish between hand-made movements (which they mirror) and tool-made movements (which are not mirrored).

The purpose for which these mirror neurons have evolved seems to facilitate communication between individuals of the same or at least related species (monkeys and humans, for example). It has also been postulated that mirror neurons play a role in the development of empathy and to imagine another person’s state of mind. Mirror neuron systems may be involved in dance routines, sports, speeches in which gesticulations are involved, etc. and it has been postulated that in sufferers of autism the mirror neuron system may be impaired. However, conflicting data on this hotly debated issue do not currently allow a definitive conclusion. Whether mirror neurons exist in insects and are, for instance, involved during the migratory phase of locust hoppers when the action of one individual jumping forward is followed by other nymphs nearby, is a possibility, but hasn’t yet been investigated. For mammals and birds, however, there is no doubt that mirror neurons are present and I wonder: Was that perhaps the reason why our dog always began to runaround when our children started running up and down our yard and the reason why our children were trying to lap up milk from a plate like our cats did?

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Lowering their Heads and Facing East

Why do sunflowers behave this way?

Anyone who undertakes a train journey in late summer from Helsinki to Beijing (like I did quite some years ago), will see extensive fields of sunflowers before the train leaves Europe and enters Asian territory. What is remarkable about the sunflowers is that they all face one direction and observing that, I thought the sunflowers probably orient themselves towards the sun. But according to a recent study by Horvath and co-workers, this is not so, because following a short period of full bloom during which the flowers do orient towards the sun, they then gradually bend downward and become ‘locked’ in a direction to face the East. (Now the beautiful and patriotic song “The East is Red” 东方红, never mind the words, enters my head and reminds me of the time I heard it daily while spending 3 weeks in China by invitation of the Chinese Academy: you can guess how long ago that must’ve been!). However, sunflowers, which like many fruit and vegetable plants originated in the ‘New World’, have other reasons to turn eastward.

In the past, several reasons had been advanced to explain why after the flowering period sunflower inflorescences no longer track the sun, but remain east-oriented. Yet none have been tested reliably and the new explanation for the first time takes into consideration the place of origin of the sunflower plant, the astronomical data of the sun’s position, the meteorological data of diurnal cloudiness, the time-dependent elevation angle of mature sunflower heads and the absorption spectra of the inflorescence’s front and back. An earlier suggestion was that a non-skyward orientation of mature sunflower heads would make it more difficult for birds to peck at the seeds. While true, it does not explain why the flowers should face east. Another attempt to explain the eastward orientation was that it would reduce the heat load at noon, but west-facing flowers would have the same advantage, so why ‘east’? It has also been assumed that east-facing allows greater light reception in the morning and speeds up drying of morning dew, thereby reducing fungal attack. That an easterly orientation promotes attractiveness to pollinators has been suggested, but by the time the sunflower heads get ‘locked’ in the easterly position, pollination has long been finished and the idea that an easterly orientation and the lower head temperature could be advantageous for seed maturation was not supported experimentally.

What appears to be crucial is that there is a 10-50% surplus energy absorbed by an east-facing sunflower inflorescence compared with other directional orientations. This could indeed accelerate the evaporation of morning dew, but what is the easterly orientation due to? It has seemingly something to do with the region the sunflower plant evolved, namely Boone County in North America, which regularly encounters cloudy afternoons. If afternoons are cloudier than the mornings, then east-facing inflorescences have an energy advantage of around 10% over west-facing flowers and an up to 50% radiation excess over south-facing flowers, taking into consideration absorption spectra of the inflorescence and the back of the heads. Maximum radiation absorption should be advantageous for seed production and maturation. The easterly orientation seen even in domesticated European sunflowers is likely to be a genetic trait that evolved in response to the meteorologic conditions of cloudy afternoons in the region that sunflowers evolved in North America.

Given that solar panels are usually directed south and direct sunlight is most intense at noon, are sunflowers ill-adapted, or do sunflowers perhaps ‘know more’ than solar panel engineers? Sunflower heads are tilted, looking downward and under such conditions the lower angle of the sun in westerly and easterly position is crucially important. But adding afternoon cloudiness into the calculation is what then causes the East to turn into ‘the winning formula’ for Helianthus annuus (the sunflower).

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.