Solar eclipse 12 August 2026 in The Netherlands captured with digital camera equipped with Neutral-density filters

SONY RX10-iv 600mm ISO200 f/4 1/15 sec. time 20:02
Dimensions of the sun on this image: 780x725 pixels
Original image: 5472x3648 pixels.

The solar eclipse 2026 was a total eclipse in Iceland and Spain, and partial in The Netherlands. The weather was perfect, completely cloudless, but a littlle bit too hot at first. The maximum was around 20:10 in the evening, with 90% coverage. Because the sun was low on the horizon, a location was required with a good view to the West without trees or buildings, in this case a nature reserve (Westbroekse Zodden). The last contact was around 21:03 and sunset at 21:10.

At a previous solar eclipse I used an improvised method to photograph the eclipse. This time I used photographic HOYA PROND EX - ND500 filters. These are Neutral-density filters (ND filters) which reduce the intensity of all wavelengths of light equally, giving no changes in hue of color rendition. The filters can be combined. To ensure that the camera sensor would not be damaged, I used two of them on top of each other (1) and on top of the standard UV filter. Still, I didn't dare photograph the beginning of the eclipse and waited until the maximum. 

Manual focus required (∞). I used diaphragm f/4,0 because higher settings didn't work well. I used the SONY RX10-iv with maximum zoom 600mm, see pictures. I succeeded in making a few sharply focused photos but I stopped at the moment the sensor seem to produce distorted images. Luckily, it turned out afterwards that the sensor was not damaged! 

©A.B.

Subjectively speaking, the eclipse at the moment of the maximum coverage of 90% was somewhat disappointing; it didn't get really dark. However, the colors in the landscape did fade noticeably, and it became less warm. The human side: people came together from all over to admire the eclipse at the hospot I had chosen. It was a social happening. There was a cheerful and friendly atmosphere.

©A.B

Next solar eclipse: 2 Aug 2027 (49%).

 

Notes 

1. Warning: don't tighten the filters too much! I couldn't get mine apart anymore! I eventually managed to get mine loose again after all. One ND500 filter equals 9 stops down. Two of them equals 18 stops down! So I have used more than recommended ND100.000 (16.6 stops) and coud have easily made pictures of the start of the eclipse. See for table ND filters and stops: Fotograferen met filters and Zonsverduistering fotograferen: de complete gids voor 12 augustus 2026. I only found this website after the eclips.

 

Previous blogs

• Zonsverduistering fotograferen met een gewone digitale camera? Het kan! (29 maart 2025) Solar eclipse with standard digital camera. 31 Maart 2025
• Maansverduistering Maandag 21 januari 2019. Lunar eclipse.  21 Jan 2019
• Totale maansverduistering maandag 28 september 2015 groot succes ondanks slechte weersvoorspellingen. 28 Sep 2015

Spiderweb colors violate the rainbow rule

Spiderweb (overview). Backlight [1]

According to the laws of physics, rainbows caused by sunlight always appear in the section of sky directly opposite the sun [2]. Here I show that spiderwebs violate this rule by pictures of spiderwebs with backlight resulting in rainbow-like colors as well.

Kruisspin / Garden Cross Spider / Araneus diadematus 

Detail. length ~ 1 cm / 0,4 inches

Straight white lines demarcate a sector of the spiderweb circle
that lights up selectively. The rest is faintly visible and colorless.
The lines meet at the center of the web,
and seem to point towards the sun.

detail of previous picture. Click to enlarge.

So the part of the spider web circle that lights up seems to be a segment which points to the sun [3]. Furthermore, as shown in the previous blog, the threads of the web consist of many small segments with different colors. Contrary to the previous blog, these pictures are taken towards the sun. The fact that colors are seen at all contradict the physical rules for the formation of a rainbow by the sun. A possible explanation could be that the spider web threads are not made up of water droplets but of proteins...   

Garden Cross Spider
This little spider had nothing to eat for a week.
Finally she caught a fly! Enjoy your meal!
Note the difference in size!

An adult Garden Cross Spider
built its web on the window of the barn door.
Fortunately we could still use the door!
By the way: this location is perfect to investigate the effect
of different directions of the sunlight
because you can move the door without damaging the web!
Addtionally you can photograph the web from both directions!

 

Notes

1. The main light source, the sun, is behind the spider, facing the camera and photographer. Note: in Dutch this is called 'een tegenlicht opname'.
2. Thanks Rolie Barth and Matt Young for pointing this out. See for example wikipedia article Rainbow.  
3. However, I did not investigate this effect systematically!

Previous blogs

• Accidental discovery of the ultra finestructure of the web of the Garden Cross Spider [+additional pictures].  29 June 2026
• Araneus diadematus. Panda's Thumb Photography Contest. July 27, 2026

Links

• Spider web colorations on Youtube (high quality photographs, much better than mine!)
• Glistening spider silk with beautiful pictures of Dietrich Zawischa

Read more...

Accidental discovery of the ultra finestructure of the web of the Garden Cross Spider [+additional pictures]

Kruisspin / Garden Cross Spider / Araneus diadematus ©GK
One radial line is visible.

Yesterday my attention was drawn by an orange coloured spider illuminated by the sun. I was forced to underexpose the photo by 2 stops to get the right exposure of the spider. It appeared to be the common Garden Cross Spider (Kruisspin). But what me surprised the most was one thread (fiber) of the web:

Here is a detail of the thread (cut into two parts). A remarkable pattern of very fine stripes with all the colours of the rainbow emerged. I've never seen such a pattern. I expected a continuous thread. Furthermore, lengthwise along the thread, I see 3 dark lines. That would imply that the thread is not one thread, but a combination several (four?) threads.  

detail, 2x zoom, high contrast, b&w.

Why in heaven's name this very detailed structure? What is going on? How does the spider manage to create this pattern? And what is its function (if it has a function at all)?

Afterwards I realized that I have been extremely lucky. First, the sun must illuminate the web at the right angle to make the thread and the pattern visible. Spider webs are supposed to be invisible to be effective! In the shadow, you see absolutely nothing. I was also lucky that a thread was nearly parallel to the camera sensor, which keeps it in focus over a sufficient length of the thread. Secondly, I underexposed the photo to get the spider right. As a side effect the pattern appeared. I almost never underexpose a photo. Normal or overexposure make the fine details disappear. Thirdly, I was lucky there was no annoying wind that could move the web. Because web threads are so thin, the slightest breeze brings them out of focus. Wind is the enemy of macrophotography. Finally, it was a clean and fresh web in the garden, so no house dust attached. 

 

The science behind it

I know that scientists have analysed the chemical composition of the threads. The threads are made of Spidroins proteins that form the majority of spider silk fibers. 

Major Ampullate Spidroin Structure. The repetitive domains of major ampullate (dragline) silk consists of alternating regions of polyalanine and glycine-rich sequences. These repetitive domains are important for the strong and elastic features of the dragline silk fibers ( Xu and Lewis,1990). (Synthetic Spider Silk Production)

It seems very unlikely that what we are seeing here are alternating regions of  Alanine and Glycine (Amino Acids) rich regions in the proteins. More likely we see crystalline and non-crystalline regions in the threads? Maybe different spidroins? I have really no idea. There is a lot to explore...

Surprisingly, I did not find similar pictures of the fine structure of spider web threads in the relevant Wikipedia pages, Spidroins, Spider silk and Spider web.

 

June 30 / July 1: some edits in the text, +1 picture.

 

Additional pictures

8 July 2026

[4684-detail] original positions. GK.

[4669-detail] main thread. GK.

[4658-detail] original positions. GK

[4657-detail] original positions. GK

 

[4654-detail] original positions. GK.

All pictures with a factor -2 to -3 stops under-exposure. Kruisspin / Garden Cross Spider. They are not enlarged. Macrolens Sony 90mm. Threads have direct sunlight from behind the photographer. No artificial light source. All threads except one [4669] are connecting threads. See here for the anatomy of a spider web.

What stands out is that no threads are the same.  Can all this be explained by pure optics??? That is: no internal structure of the threads???

 

9 July: Meanwhile, I have made pictures with the sun in front of the camera ('tegenlicht'). They also show the usual patterns depending on the angle of the sun's rays. Direct sunlight is necessary. The sun must not be wholly or partially covered by clouds. Also, the cross bands are never visible across the entire web at the same time. This can be interpreted either as differences in the structure of the threads themselves or as a difference in the angle at which the sunbeams strike the web. The fact that the visibility of structures highly depend on sunlight is in no way an argument against the existence of structures. In biology structures are always made visible by chemical or optical techniques. For example, chromosome bands are only visible when stained, but are absolutely real.

 

Further Reading

• Optical effects on spider webs by Dietrich Zawischa (beautiful pictures with explanations)
• Accidental Observations by Dietrich Zawischa is a collection of remarkable optical effects in everyday life. (With thanks to Matt Young) (22 July 2026)
• Wikipedia: Orb web spiders, Orb web construction

Are there biological facts that the theory of evolution does not explain and does not need to explain?

The theory of evolution is the overarching unifying theory in biology. Are there biological facts that the theory of evolution does not need to explain? Or does the theory of evolution have to explain every fact about life? According to the theory of evolution every species and every individual of a species is the result of evolution. That would imply that every feature of an organism must somehow be explained by the theory of evolution. 

Aerodynamic forces on a bird (Videler, 2012)

Even at the time when I was a student and attended evolutionary biology courses and did lab experiments on evolution, I had the vague idea that the theory of evolution was incomplete, although at the time I couldn't say why, or what exactly was missing (here). There is so much to explain, and "A change in gene frequencies over time" and "Differential reproduction of heritable variation" seem far too simple for the task. Yes, there was a Second and Third Evolutionary Synthesis, but still a lot was missing. Obviously, the planetary, geological and cosmological context of evolution is often missing in the textbooks. Last year I blogged about the fact that evolution textbooks are suffocating: very low levels of Oxygen!  My list of top 20 evolution books (blog) reflects my preoccupation with the question of what is missing. Furthermore, physicist Rolie Barth pointed out physical factors and constraints in evolution (blog) [1]. At the other end of the spectrum: is evolution supposed to explain human behaviour, intelligence, consciousness, psychology, language, culture, civilization, war? What is the scope of the theory? Where does it end?

A few days ago I had an interesting discussion with google-AI about the question: Are there biological facts that the theory of evolution does not need to explain?  The initial answers seemed incorrect and incomplete. So, I demanded better answers and google-AI came with surprisingly insightful answers:

1. What evolution does NOT need to explain: The physics of how cells physically move, stick together, or split. For example, when a sheet of cells bends into a tube, it follows basic laws of fluid mechanics and surface tension.
2. What evolution DOES need to explain: Why the cells bend into a tube at that exact moment, in that specific location, to form a spinal cord. The timing, the instructions, and the genetic switches that trigger those physical movements are entirely shaped by natural selection.
3. What evolution does NOT explain: The electromagnetic forces that allow a hydrogen bond to form between Adenine and Thymine. That is pure physics and chemistry.
4. What evolution DOES explain: Why a specific three-letter sequence (like UUU) maps to a specific amino acid (like Phenylalanine), and why this map is nearly universal across all life.
5. Evolution does NOT explain: Why a hydrogen bond forms at all, why the universe is made of matter instead of antimatter, or the laws of thermodynamics that govern energy conversion.
6. Evolution DOES explain: How life hijacked those inescapable physical realities and organized them into the intricate, Mendelian, metabolic, developmental masterpiece we call biology.

Additionally:

• Lipid Bilayers: Amphiphilic lipid molecules automatically assemble into complex, spherical, semi-permeable cell membranes when exposed to water, driven entirely by hydrophobic physical forces.
• Membraneless Organelles: Inside the cell, proteins and RNA's undergo liquid-liquid phase separation—similar to droplets of oil separating in water. This thermodynamic behaviour spontaneously forms highly organized, functional compartments (such as the nucleolus) without needing an explicit genetic blueprint directing every coordinate.

These examples can be expanded with:

Microtubules: the self-assembly of microtubules. The proteins themselves are inherited, but they self-assemble into microtubules. 

Biochemistry: See also the primacy of biochemistry as opposed to genetic determinism [2].

Bio-electricity: "Without bioelectricity, your cells couldn't communicate, your muscles couldn't move, and your heart wouldn't beat." [3]:

• The Cellular Battery: Membrane Potential
• Nervous System Communication
• Muscle Contractions (Powering Movement and the Heart)
• Wound Healing and Tissue Regeneration
• Specialized Biological Superpowers (Electroreception, Electrogenesis)

Quantum effects: photosynthesis. 

Mechanical forces: Venus flytrap [4].

Van der Waals forces that hold molecules together (Gecko).

Hydrogen bonds (DNA bases).

Aerodynamics (birds, bats, insects), hydrodynamics (fishes, dolphins, sharks, blood flow).

Gravity: Effect on body size (scaling laws).

Geomagnetic field: is used by pigeons for navigation

Ultrasound navigation (bats)

etc. 

 

It seems very reasonable that evolutionary theory doesn't need to explain physical and chemical phenomena, because it is a biological theory. Physics and chemistry do explain physical and chemical phenomena. A biological theory can take them for granted, isn't it?

However, there is a problem. For a full scientific explanation of the evolution of life on earth, one cannot do without additional non-biological explanations. But organisms are undivided wholes. They can't be subdivided into biological, chemical and physical parts. So, must we conclude that the theory of evolution, as a biological theory, by definition is incomplete? [5]. Could it be that the theory only has to explain how biological things have evolved, and not all the details of how they work precisely? Would it be enough to demonstrate which genes and which mutations are involved in creating a specific trait and how it contributes to fitness? Does the theory need to include aerodynamics to explain the origin and evolution of flight? Finally, if new scientific discoveries are made on a daily basis, how can the theory of evolution ever be complete? I am afraid that the question of the scope and completeness of the theory of evolution is a rather complex and elusive question. Maybe, several quite different questions. Anyway, the question is too wide-ranging and too tricky to settle in one blog post. 

Notes

1. See also this blog where Rolie Barth explains that "Protein evolution can draw from a reservoir of a limited number of physically possible structures".
2. Nick Lane say about the primacy of biochemistry contra genetic determinism: Genes evolved simply to stabilize and optimize these already functioning biochemical pathways, rather than starting from scratch to build the cell. Also: The electrical origins of life!  
3. According to https://gemini.google.com 
4. Fast cell wall softening causes Venus flytrap closure, Science, 11 Jun 2026
5. Note: Could that be the cause of my gut feelings about the incompleteness of the theory of evolution half a century ago? 

Preliminary Conclusions

17-19 June 2026

• The Theory Of Evolution is a high level abstract paradigm that generates research strategies to investigate the details of structure and function of species.
• The Theory Of Evolution can be so compact because all the details are supplied by the biological subdisciplines, chemistry, physics and so on.
• Another reason why the Theory of Evolution is so compact is that it does not predict 'the brute facts of life': the existence of Kangaroos, Penguins, Anteaters, Hummingbirds, Bats, Octopuse, Sundew, Ocean sunfish, Platypus, Eukaryotes, Sex, Genetic Code, Split genes, the structure of DNA, etc. (historical contingency).
• The two hardest problems of The Theory Of Evolution are the origin of life and the origin of consciousness.
• Common descent predicts deep similarities of all life, and indeed this has been found on the genetic, biochemical, developmental and anatomical level, although the extent and specifics of similarities cannot be predicted in advance and often have surprised scientists.

Read more...

Autonome wereld en theodicee bij Taede Smedes (3)

"Het blog over Autonome Wereld bij Taede Smedes (2) is een van mijn meest bekeken blogs. En er kwamen soms vreemde reacties. Iemand die je een Taede Smedes-kenner zou kunnen noemen, schreef dat Taede Smedes nooit over het probleem van het kwaad had geschreven. Dat vond ik een vreemde bewering.
In een vorig blog (1) schreef ik over het probleem van het kwaad zoals beschreven in het boek God en Darwin van theoloog-godsdienstfilosoof Taede Smedes. Het probleem werd in dat boek maar heel kort aangestipt omdat het boek over een ander onderwerp ging. Toch werden er in dat boek zeer belangrijke en revolutionaire uitspraken gedaan. Sommigen (2) beweerden dat Taede Smedes nooit iets over het probleem van het kwaad had geschreven, en daaruit volgde op de een of andere manier dat ik het helemaal mis had. Of zo iets. Onzin! Onwetendheid! Smedes heeft wel degelijk over het probleem van het kwaad geschreven in zijn boek God en de Menselijke Maat (2006). Met name in Hoofdstuk 11 (toelichting, literatuurlijstje) (bewijst ook dat hij zich met de literatuur heeft beziggehouden)." 

Tot zover een draft blog dat ik nooit heb afgemaakt. Ik publiceer het nu ongewijzigd zoals het sinds 2011 als draft is blijven staan. De aanleiding is een blog van Taede Smedes: Lieke Marsman – Een oproep tot leven, 4 juni 2026. Dat blog opent met de woorden:

"Ik heb het feit dat kanker bestaat altijd gezien als een van de belangrijkste argumenten tegen het bestaan van een bovennatuurlijke God. ... Dat kanker bestaat, toont voor mij aan dat een bovennatuurlijke Schepper-God – zoals voorgesteld in het christendom – niet kan bestaan. Zo’n God is voor mij dan ook een illusie."

Je kunt in ieder geval vaststellen dat Smedes in de loop der jaren consistent is gebleven in dat opzicht [3].

Noten

1. Autonome wereld en theodicee bij Taede Smedes (2) Het probleem van het kwaad, 28 november 2011. 
2. Uitgerekend filosoof Jan Riemersma heeft vele malen gezegd dat je vooral Taede Smedes moest lezen. Overigens is het helemaal niet relevant of Smedes 'nooit over het probleem van het kwaad' geschreven heeft. Het gaat er om wat hij wel geschreven heeft. Daar doe ik het mee.
3. Dit blog van Smedes over hetzelfde onderwerp had ik nog niet eerder gezien: Sluit zinloos lijden het bestaan van God uit? 17 mei 2010.

A likely breeding case of the Common Hoopoe in the Netherlands

Common Hoopoe / Hop / Upupa epops ©GertKorthof

The Hoopoe is a rare and unique bird in The Netherlands. It has an unusual combination of a movable crest like that of a cockatoo, and a long beak curved slightly downwards like that of an Eurasian Curlew (wulp). The plumage is a combination of an inconspicuous brown and a striking black-and-white pattern. The food-seeking behavior is mostly on grasslands and clearings in the forest, but it breeds in tree cavities like a woodpecker.

©GertKorthof

Recently, I was fortunate enough to watch this beautiful bird in the wild in The Netherlands. It landed on a bare spot in the forest about 20 meters (65 Feet) away from where I was walking. From my position, I could observe, photograph, and film it perfectly. After a few minutes, it flew away. I was able to make a short video:

A short video clearly shows the hurried way of foraging.

Evidence for a breeding case

The bird is very busy gathering food for short moments during most of the day on different locations and returning again and again. It has been observed that the birds repeatedly fly with food in their beaks in the same direction. They are usually very relaxed, but this bird was very busy. I have seen pictures made by another birder that clearly show a Hoopoe flying away with an insect in its beak. That is the best, albeit indirect, proof of a nest with young. This is not the same as fledging, the stage that the young leave the nest. Only then can it be called a success.

I have submitted my observation to waarneming.nl. The image recognition system (ObsIdentify) resulted in a 100% certain identification. Not really a surprise for an easily recognizable bird. This observation appeared to be under embargo and is only visible to myself and authorized persons. So, I can't see how many observations have been submitted. My observation was automatically approved. This shows that manually approved observations of the bird on the same location must have existed already at that moment. Despite its rareness, there are a lot of Hoopoe observations visible in waarneming.nl at many locations in The Netherlands, but these aren't breeding cases.

How rare is the Hoopoe in the Netherlands?

Hop Upupa epops. breeding 2021-2023 SOVON

Hop Upupa epops. Non-breeding 1989-2014 SOVON

See for more data:  SOVON [3]

 

Fun facts

Peterson, Mountfort, Hollom, Kist 1964 [2]

My first serious bird guide, at the time it was referred to as 'De Kist', now 62 years old, has a Hoopoe on the cover! How charming! They placed a very rare breeding bird on the cover! Field characteristics of the Hoopoe:

"Searches for food mainly on open ground. Nests in tree cavities and the like. Very rare breeding bird of open woodland. Reappeared for the first time since 1943, after 30 years. Rare migrant from mid-August to late October and in spring in April and May." (page 195)

The map in this bird guide shows that the Netherlands lie above the northern border of the breeding area. Birds showing up in The Netherlands could be called pioneers venturing into unknown territory. This could explain why the number of birds fluctuates from year to year. I imagine that after a good breeding season in southern countries, young birds migrate north. Their usual food grasshoppers and lizards are relatively rare in our country, so the pioneer birds must adapt to other prey [1]. They must be flexible.

A bird encyclopedia published between 1770 and 1829 DE NEDERLANDSCHE VOGELEN: [4]

De Nederlandsche Vogelen. (Grutto op omslag)
Compare with a modern bird guide.

 

3 pages about the 'UPUPA' or HOPPE. [4]

 

The illustration is of high quality and is absolutely sufficient to identify the bird. The author describes the bird as a rare breeding bird. It was difficult to locate the nest of the bird. Between 1747 and 1778 it has not been seen. This shows how irregular the presence of the bird was at the time. However, the most striking fact in modern eyes is the fact that the author received a (dead!) breeding pair of Hoopoes complete with eggs and part of the 'nest' that had been captured (?) shot(?) from the wild! Fun fact: the author mentions that the famous philosopher Aristotle already knew the bird [5].

 

Title plate of book III clearly showing a Hoopoe..

Finally, the Hoopoe is present in the holy book of Christians, The Bible: " It is mentioned in the Old Testament as one of the birds that the Israelites were forbidden to eat under the dietary laws of the Mosaic Law." [6],[7].

 

Notes

1. R.M. Teixeira (1979) Atlas van Nederlandse broedvogels. page 212-213. 
2. Dutch translation of: Peterson, Mountfort, Hollom 1964) A Field Guide to the Birds of Britain and Europe. Translated and adapted by Mr. J. Kist.
3. SOVON, (Stichting Ornithologisch Veldonderzoek Nederland, Sovon Dutch Centre for Field Ornithology) is the most reliable source of the numbers of bird species in The Netherlands. The most recent report is Broedvogels in Nederland 2024. The Hoopoe is described on this page with an estimated number of 5-7 breeding cases. (information from Klaas van Dijk 2 Jun 2026).
4. DE NEDERLANDSCHE VOGELEN free online edition. 'Hoppe' is the old name of the Hop.
5. I checked it, and indeed: THE HISTORY OF ANIMALS by Ari" target="_blank">on this pagele, tr with an estimated number of 5-7 breeding cases. nslated by D'Arcy Wentworth Thompson, Book VI.
6. It is mentioned in the Old Testament as one of the birds that the Israelites were forbidden to eat under the dietary laws of the Mosaic Law. Leviticus 11:19, Deuteronomy 14:18. Unclean for consumption: the Hoopoe is grouped with other "unclean" and detestable birds (like vultures and bats). It is indeed repeatedly mentioned in the literature that droppings accumulate in the nest and are not cleaned up. Understandable that it is an 'unclean bird'. However, it is possible that this fact has been endlessly copied without first-hand observations! Most birds keep their nests clean due to the risk of infection. [added: 2 Jun 2026]
7. Vogels in de Bijbel geeft 21 vogels, waaronder de Hop, maar ook de Struisvogel! Dat kan natuurlijk niet, want de Struisvogel komt alleen in Afrika voor. [4 juni 2026]

Read more...

Turkse Tortel (Streptopelia decaocto) met afwijkend oog en snavel

Turkse Tortel ( Streptopelia decaocto ) afwijkende snavelvorm,
normaal linker oog. (13 mei 2026) ©Gert Korthof

  

misvormd rechter oog en de
bovensnavel groeit over de ondersnavel heen.

 

de nekveren lijken ook niet normaal

Het beestje kon nog zaadjes oppikken van de grond ondanks de misvormde snavel. Er komen dagelijks Turkse Tortels op het vogelvoer af, en die zien er allemaal normaal uit, maar deze afwijkende vogel had ik nog niet eerder gezien. Hij/zij was redelijk actief, maar had moeite met zaadjes oppikken. Hij kon normaal vliegen. De volgende dag zag ik hem weer.

Ik neem hier het Google AI overzicht letterlijk over:

Een Turkse tortel met een misvormd oog en snavel is vaak het slachtoffer van een ernstige, veelvoorkomende vogelziekte genaamd Trichomoniasis, ook wel bekend als "Het Geel". Hier is wat u moet weten over deze situatie: 

Oorzaak (Trichomoniasis): Een parasiet (Trichomonas gallinae *) veroorzaakt ontstekingen in de snavelholte, keel en slokdarm. Dit leidt tot een gelige, kaasachtige aanslag, waardoor de snavel misvormd lijkt, de vogel moeite krijgt met slikken en benauwd wordt. 

 Symptomen: De vogel oogt vaak lusteloos, verwaarloosd, zit bol en is broodmager. Het oog kan aangetast lijken door de algehele infectie in de kopregio. 

Alternatieve oorzaak: Soms kunnen tekenbeten op de kop ook zorgen voor ernstige ontstekingen en misvormingen bij tortels. 

Besmettelijkheid: De ziekte is erg besmettelijk voor andere duiven en vogels (via voedsel- en waterplekken), maar niet gevaarlijk voor mensen, honden of katten.   

Het advies is drinkbak verversen omdat de besmetting overgebracht kan worden op andere vogels. Dat heb ik direct gedaan. Tevens heb ik een druppel biologische appelazijn in het drinkwater gedaan.

*) "Turkeys and chickens can become infected through drinking water or food contaminated with feces, saliva or crop secretions. Because the trichomonads do not survive for long outside the bird, transmission must occur rapidly. Newly introduced, unquarantined birds, as well as wild birds may be an important source of introducing the infection to domestic birds and vice versa." source: wikipedia.

 

"Het geel, veroorzaakt door Trichomonas gallinae uit het trichomonas-geslacht, is een parasitaire protozoa aandoening van de bovenste luchtwegen die vooral duiven en soms ook zangvogels treft. Meestal komt het bij duiven voor door onderling snavelcontact." bron: wikipedia pagina Het geel.

 

Tortels in de problemen...

"Een aantal weken terug kregen we een eerste Turkse tortel over de vloer die een wel heel bijzonder probleem had: zijn hele kop was gezwollen en de beide ogen zaten dicht. ..." lees verder:  Natuurhulpcentrum (België)

 

Natuurpunt.be 

Informatie over de behandeling op natuurpunt.be. De veterinaire behandeling van grote vogels (vanaf duiven) gebeurt met tabletjes Trichocure of Spartrix.

 

Postscript 18 mei 2016

normale snavel

afwijkende snavel

Vergelijking snavels van normale (L) en afwijkende snavel (R) van Turkse Tortel. De normale bovensnavel is iets langer dan de ondersnavel en buigt naar beneden over de ondersnavel heen. (ik denk dat dit voor alle duiven geldt). Bij de afwijkende vorm is de bovensnavel duidelijk langer en buigt zijdelings langs de ondersnavel naar beneden, zo ongeveer als een kruisbek.
De gehandicapte Turkse tortel bleef de volgende dagen onze tuin bezoeken en ik merkte op dat zijn rechter oog zich enigszins hersteld had. En hij heeft leren eten met de afwijkende snavel. NB: ik heb geen officiele diagnose van Trichomoniasis besmetting, maar het lijkt er op.

 

Read more...

Physicist Charles S. Cockell: "DNA and its entourage". The Genetic Code is non-random.

Evolution is the transformation of species into slightly modified species. The origin of species is solved in principle. However, the origin of life is a fundamentally different problem. Darwin avoided discussing the origin of life. It is the hardest problem of biology and it still has not been solved yet. Whereas the details of evolution can be described as a puzzle, the origin of life must be characterized as an intractable problem.

A crucial step (although not the first step) in the origin of life was the invention of DNA and the Genetic Code. DNA has become a defining property of life. But how DNA acquired its meaning is still a mystery. How could a relatively chemically inert non-enzymatic molecule (DNA) become useful, even indispensable, for life? DNA itself could not have been involved in the origin of life (Think about this...). There must have been something before DNA. 

In the literature the Genetic Code is usually presented as a table in which all 64 combinations of 3 bases A, T, C, G are 'associated' with 20 Amino Acids. These associations could be made in many different ways. Nature got stuck to one system of associations called the Genetic Code table. In the book The Equations of Life: How Physics Shapes Evolution, Chapter 7 'The Code of Life', physicist Charles S. Cockell notices that the Genetic Code table is non-random. This is an important observation. The assignments of base triplets to Amino Acids (AAs) is non-random. When looking at the table It is immediately clear that there is a pattern. Secondly, there is redundancy: many Amino Acids are coded by more than one base triplet. But there is also a pattern. This is all known very well [4].

However, Cockell also notices that there is something special about nature's choice of the twenty Amino Acids. There are many more natural Amino Acids available than those twenty. So, why those twenty? Random? Accident? Or are they the most suitable for their task? He refers to a publication [1] that argues for a non-random choice. The authors reasoned that there are 3 properties of Amino Acids that are important for constructing a protein: (1) the size of an Amino Acid, (2) the charge, (3) hydrophobicity (repelling water) [3]. Together those properties determine how the protein behaves and what it can do. In principle proteins could be constructed from one or a few Amino Acids. But most useful proteins consist of a diverse mixture of amino acids. Proteins are defined by a unique sequence of AAs to fold into a complex 3D shape. Also, it is not useful to have many AAs with the same hydrophobicity, or the same size or the same charge. The best toolkit for life would have an even distribution of AA properties that does not overlap too much. To test for optimality the authors tested a set of fifty AAs found in the Murchison meteorite. The reason? They assumed that AAs found in the meteorite would represent the set of AAs found on the early Earth. What they found was astonishing, writes Cockell:

"When they compared the twenty amino acids used by life with a million alternative bundles of amino acids randomly chosen from the fifty in the meteorite, the twenty used by life had better coverage and combinations of all three of the key factors than did any other set. ... they seemed to be selected by evolution to give a wide range and even distribution of properties that might be useful in proteins." ... Of a much expanded set of seventy-six AA, not a single group out of a million possible alternatives outperformed the natural set.". (chapter 7). 

Cockell concludes that the twenty AAs used by life are not random. That was new to me. But there is one important aspect Cockell doesn't mention: the AAs must also be suitable to be attached to a transfer RNA (tRNA) and to be processed by the ribosome. This is a crucial property. It is the biochemical implementation of the Genetic Code table. There could be differences in suitability. This must be investigated. Furthermore, all AAs are associated with 1 or more triplet codons (redundancy). The question is: how is the association made between a base triplet codon and the AA? And how did that originate in the first place? The structure of tRNAs does not show a direct chemical bond between codon and AA. Is it a random choice? That could certainly be the case because AAs and triplet codons (bases A, T, C, T) are different chemical compounds, yet they are somehow connected. Or is there a logic in the associations? Is there a pattern? Much research has been done to solve this question. No definitive answer yet. Cockell does mention this. But at least he pointed out a new aspect of the origin of life and the Genetic Code table to me.  

 ______

In this blog I did focus on the origin of the Genetic Code. The origin of the Genetic Code is in fact the origin of DNA-based life: bacteria, animals and plants. It is also the origin of protein and enzyme based life. The origin of DNA and proteins are strongly intertwined. DNA on its own has no use and proteins can not exist without DNA. DNA cannot self-reproduce, it needs enzymes. But proteins cannot self-reproduce either. A specific protein consists of a unique sequence of Amino Acids. Unique proteins do not self-assemble spontaneously. The only way to reproduce such a unique sequence is on the basis of another unique sequence: the unique base sequence in DNA. In other words: DNA and proteins depend on each other. This not a promising situation to start life. Hence, the hypothetical RNA world was developed (which is not without its own problems!). Keep in mind: the origin of the Genetic Code is not the same as the origin of eukaryotes. Bacteria are also DNA- and protein-based life forms. All life on earth uses the same Genetic Code, including viruses.

Physicist Charles Cockell used the expression "DNA and its entourage" [2]. And that is a misleading description. I hope readers recognize this as DNA-centric thinking. The cell and the cellular machinery are not an "entourage"! It is an equally important part of the cell! DNA is not the master of the cell! The cell is not the servant of DNA!

Notes

1. Gayle, Freeland (2011) Did evolution select a nonrandom "alphabet" of amino acids? Astrobiology 
2. "An entourage is a group of attendants, assistants, or close associates who accompany and work for an important or famous person". 
3. There exist another list of properties of AAs: polar versus non-polar; acidic versus basic. [5 May 2026]
4. For example there is a famous article by Freeland and Hurst (1998) The Genetic Code is One in a Million, Journal of Molecular Evolution. See also their April 2004 article Evolution Encoded in Scientific American [5 Jun 2026]

 

Further Reading

• Can AI simplify the alphabet of life?  Generative AI design yields functional proteins with only 19 amino acids. Science, 30 April 2026. The design functional bacterial proteins without the amino acid isoleucine.
• Toward life with a 19–amino acid alphabet through generative artificial intelligence design.  Science, 30 April 2026. "no known free-living organism uses an alphabet of fewer than 20 amino acids. This raises a fundamental question: Can a viable cell be constructed with a reduced amino acid alphabet?" A statement against Cockell: "Computational protein modeling also indicates that as few as 9 to 12 amino acids could, in principle, encode all protein folds."

 

Previous DNA blogs

• If the blueprint of the embryo is not in DNA, then where is it? Alfonso Martinez Arias. A very convincing argument for the cell-centric view of life 14 March 2026
• Richard Dawkins admits: DNA is *not* a blueprint! But Dawkins still got another metaphor wrong! 16 February 2026
• Think about this:  09 February 2026
• Gene-centrism is bad biology. Here is why. 17 December 2025
• What is DNA-centrism? Why is it wrong? 10 November 2025