Insects that Scampered or Clambered into Amber

On purpose or unplanned?

I once sent my children to school with a big apple that was inside a glass bottle with a narrow neck. I told my children to show it to the teacher and ask her how the apple got into the bottle. The teacher said to them that your father is a scientist and he probably knew how to carefully remove the bottom of the bottle and stick it on again once he’d put the apple inside. That, of course, hadn’t been how I’d done it (I had fastened a bottle facing downward, lest water got in, over a tiny apple still on the tree, before it got big). What this has to do with amber and insects inside it? Well, how did they get there?

Amber is used in expensive jewelry, but it’s not a stone or mineral, but the hardened resin that had oozed out of conifer trees like pine and spruce millions of years ago. What interests biologists are their frequent inclusions, primarily arthropods like mites, spiders, centipedes and insects. But even bigger animals like frogs, lizards have been recorded. The oldest ambers with inclusions are those 130 million year olds from Lebanon, while those from Myanmar, known as Burmese Ambers and famous for their biological inclusions, are considered to be approximately 100 million years old. The famous Baltic Amber, used in the “Amber Room” celebrated as the “Eighth Wonder of the World” (the whereabouts of which are still lost), dates back to 34 – 48 million years ago and also contains numerous insects present at that time in Nordic forests. What has been puzzling biologists, and especially entomologists, is the presence of so many aquatic insects in the amber and a variety of suggestions have been made how these insects ended up in the sticky tree resin that ended their lives.

One possibility is that the insects happened to get stuck accidentally, but that idea can quickly be dismissed on the basis of mathematical probability and statistical evidence.  Another suggestion had been that coniferous resin flowed into water-filled tree holes and the aquatic insects living in these tiny water bodies were trapped by the resin. However, many of the trapped aquatic insects represented species that do not visit water-filled cavities of trees. Somewhat similar was the suggestion that the resin flowed down the tree’s bark and contacted on its way to (or upon reaching) small water bodies, insects that got encased by the resin. But once again there were objections to that theory just as there were to the idea that wind could have blown the insects onto the resin and caused them to adhere and get stuck never to free themselves again. The three theories have in common that the aquatic insects ended up in the resin by accident, but the fourth suggestion has it that some insects were attracted to the resin by its glistening appearance, resembling water droplets. However, what exactly attracted the dispersing, flying, aquatic species to the resin remained unknown.

To solve that question Horvath and co-workers in Hungary carried out field experiments with sticky surfaces that polarized the light, reflected from the surfaces to different degrees and angles. They then analysed the taxonomic positions and numbers of insects that had got stuck on the surfaces and concluded that it was not simply the “shininess” or “brightness” of the sticky sheets, but the degree and angle of polarization. The result does, of course, agree with the known observation that insects, which depend on water to deposit their eggs in it like mayflies, dragonflies, stone- and caddisflies, identify water bodies not by their colour or smell, but by their polarization characteristics. The result was also in agreement with the published report representing the ancient insect fauna. So, does that solve the question how water-seeking insects ended up in the resin as ‘amber inclusions’?

Perhaps not, because in a recent 2021 publication by Mario Schädel et al., the authors reported that they had examined a piece of Burmese Amber with an assemblage of over 100 specimens of immature stages of a parasitic aquatic woodlouse relative, belonging to a group known as Epicaridea. And these tiny (and of course wingless) specimens did not possess prominent eyes at all and could not fly. So, what attracted them to the resin? Was their entrapment accidental or did the resin attract them? It’s “back to the drawing board”. But that’s science (and keeps us busy)!

© Dr V.B. Meyer-Rochow and, 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 with appropriate and specific direction to the original content.

Slip Sliding Away

But not if you can avoid it

Most scientific research starts with an observation. And when in Antarctica I watched penguins, how they walk, hop, swim and (very occasionally) slip on the ice. I, on the other hand, would have slipped and fallen all the time, hadn’t I worn special footwear with spikes, termed in-step crampons, fastened under the soles of my boots. Now penguins don’t wear boots with crampons but hardly ever slip when marching along on slippery, icy surfaces. How come? I examined the underside of the feet of a dead penguin by microscopy and found numerous tiny bumps and protuberances that could have been there to improve the feet’s steadfastness on the ice. But how about the African or Galapagos species of penguins? They never see any ice and their only risk of slipping comes from climbing onto wet and slippery rocks along the seashore. Their feet still await to be examined. And so do the feet of the Adelie penguins when in the ocean for many months and not breeding on land.

Sliding along on a slippery surface can, on rare occasions, be advantageous: for example, when penguins go into a mode of locomotion called ‘tobogganing’ or when pond skaters slide along the water surface. But more usually slipping is to be avoided as it entails the risk of getting injured. The problem is to find a compromise between reducing speed and increasing grip, i.e. stability  – and that often depends not only on structures involved in permitting or avoiding sliding, but environmental conditions. L. Heepe et al. found in 2016 that the feet of ladybird beetles (Coccinelllidae) achieve the highest attachment forces (i.e. the least amount of slipping) at a humidity of 60%, but lower and higher humidities would lead to a decrease in attachment ability. Not getting stuck too tightly is, of course, another problem that animals that possess adaptations to prevent slipping, need to control.

A pioneer in connection with adhesiveness and slipping on wet surfaces was Prof Jon Barnes, whom I had invited to give a lecture on his research with frogs when I had been in charge of our department’s weekly seminar series. Jon gave an incredibly memorable and exciting lecture, in which he described his and his colleagues’ observations on frogs of different sizes and their adhesive abilities on wet and dry surfaces. Another pioneer in the field of adhesive mechanisms in animals is Prof S. Gorb, who explains that the wet adhesive system depends mainly on capillarity (think of a wet paper plastered onto the window glass) while dry adhesiveness involves molecular interactions, known as van der Waals forces. The latter have been identified in gekkos, who are known to scuttle along upside down on the ceilings of houses. However, in frogs sitting on slanted and wet surfaces of leaves, a mechanism akin to peeling sticky tape off a surface comes into play. Their attachment forces are significantly enhanced by close contacts and boundary friction between the frog’s toe pad epidermis and the substrate. These toe pads are wet with watery mucus, assisting attachment due to the fluid-filled close coupling between the pad and the substrate, but wet adhesion alone would not hold a frog on a slippery and vertical surface. Incidentally, frogs always choose to rest on a slippery surface head-up; if the surface is turned, the frog readjusts its position as the turn reaches approximately 55 degrees. The underside of the frog’s toes features “peg-studded hexagonal cells separated by deep channels into which mucus glands open” and some vague similarities to the structures I found on the underside of the penguin’s feet, seemingly to prevent slipping, are apparent.

Frogs, of course, unlike penguins, have four legs on the ground and spiders have even eight. I had always wanted to study if each leg contributes equally to the total adhesiveness of an animal, but this question was answered by S. Gorb’s group in an interesting publication of 2014, which showed that the whole was more than the sum of all its parts. What apparently still has not been repeated was a little study of mine jn 1993 in which I reported that flies adhere to surfaces significantly longer when it is dark than under illumination. That makes sense, of course. But it needs a scientific explanation and I have so far not been able to follow up that result (but I do hope someone will).

© Dr V.B. Meyer-Rochow and, 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 with appropriate and specific direction to the original content.

A Cockroach in the Cola

Is not what you expect (or want)

During my first three years as Head of the Electron Microscopy  Centre and Professor of Experimental Zoology at the University of the West Indies in Jamaica I managed not to drink a single Cola  – not because I don’t like Cola, but because I like the brown and refreshing drink too much and knew how easily I could get ‘hooked’ on it. However, during my last and fourth summer I began to drink Colas, first one bottle a day, then two, three, even four…  until the evening when I was ready to open a bottle and spotted a huge dead cockroach in it! The next day I took the unopened bottle back to the shop where I had bought it and the shop owner apologized and assured me that he’d let the supplier know what I had found and that I should leave my name and address. A week later I received a gift from the Cola company: a wooden chest full of Colas (I won’t reveal which company): all without cockroaches in them.

Well, if that wasn’t bad enough, imagine what happened to my colleague Peter in New Zealand after he obtained a bucket of raw honey from a beekeeper friend of his: he found a dead but well-preserved mouse in the honey when he lifted the lid! Being a honey researcher, he knew of course that honey preserves and kills bacteria, but when he wanted to give me a jar of that honey I politely declined. I think he brightened up somebody else’s life with that honey, who saw Peter as a generous and caring person.

Stuff in food items that really shouldn’t be there is not as rare as many think. When I worked as a steward on a ship and a passenger wanted a plate of some buckwheat or oats (I can’t remember exactly what it was, but she insisted “raw, not boiled”), I noticed that our oats/buckwheat was crawling with tiny dark beetles. Well, since that passenger always brought her little dog to breakfast, I wasn’t too worried, thinking the oats/buckwheat would be for the dog. When I brought her the plate, I saw to my horror that she was pouring sugar and milk over the oats and commenced to eating it herself! Since she seemed satisfied, I did not ask her if she liked the breakfast, but rushed to tell my colleagues in the pantry. Incidentally, she did not get sick, but she also never asked for raw oats or buckwheat again on the trip. My first wife had a friend by the name of Heather with whom she often went shopping at the open market. This Heather took great care to examine lettuces and she wasn’t satisfied until she found one with a little slug or snail hiding in it. That, rightly or wrongly, indicated to her that the lettuce had not been sprayed with insecticides or undergone some other chemical treatment. But would this health food lover have loved to know what kind of “filth in food” is legally allowed in food stuffs sold in the USA?

The FDA (= Food and Drug Administration) stipulates that coffee beans for your coffee may contain an average of 10 mg of animal poop and 4-6% of mouldy beans. A teaspoon full of pepper can contain 40 insect fragments, while for every 8 ounces of raisins (227 g) 35 fruit fly eggs and approx. 10 whole insects are tolerated. In a 16 oz (454 g) box of spaghetti 450 insect parts and nine rodent hairs are acceptable. Two maggots in a 16 oz (454 g) can of tomatoes are not illegal and neither are 20 or more maggots of any size in a 4 oz can (113.5 g) of mushrooms. Sweetcorn, may also be contaminated and for every ¼ cup of cornmeal an average of one insect, two rodent hairs and 50 or more insect fragments or one or more fragments of rodent dung may be present. If frozen or canned spinach does not contain the permitted 50 aphids, then the FDA allows larvae of spinach worms or eight whole leaf miner bugs. Regular food controls are necessary and standards need to be set, but most of all the food must not make the consumer sick. Perhaps the aforementioned Heather is right and insect-containing food is safer than that which has undergone chemical cleansing. However, I’m not so sure about the permitted rodent hairs and dung. This reminds me of the fingernail I once found embedded in a Cadbury chocolate bar that I’d sent to the company and complained about, but then never got a reply. I changed the brand.

Bonus: THE SALON STEWARD from “Fake, Fact & Fiction”

The xylophone had sounded for dinner. The other two passengers and the two of us strode, a little off-balance but joyfully in anticipation of the usual gustatory delights, towards what on this ship was termed the ‘salon’, where our steward in his smart uniform already stood in attendance ready to bow at our entry and greet us with a witty welcome comment.

On a long monotonous sea-journey such as this one, the meals are always a gratifying respite and my husband and I were looking forward to them all day long. What a pleasure it was when our steward helped us into our comfortable dinner chairs and when we were gathered together around the dinner table in the company of the captain, the first officer, and the chief engineer.

For a full two months we had been enjoying the hospitality and attention of this fine young lad, who cleaned our cabins, who served us our meals, who never turned down a request for help, and who was genuinely friendly to us. We really liked him: “our” salon steward.

And here he came again, virile, panther-like, confident. Sure-footed despite the rolling sea, he balanced the hors d’oeuvres on a silver tray and placed them elegantly in front of us. A shock of black hair cheekily covered part of his high forehead and no matter how “jumpy” the boat and how rough the sea, never would he spill a drop of the soup or hesitate to carry three plates at once, in one hand, to our places.

Nothing seemed to go unnoticed by him and salt seller, sauce bottle, pepper shaker, jug of water, etc. were always on the table just like the starched and ironed serviettes. He was an unusual steward, who did not smoke or drink, which made him all the more amiable. Even his beard, which at first had seemed a bit out of place on a steward, now was a definite ‘plus’ and gave him character, even dignity. Were we in need of some expert nautical or geographic information and was the captain not around, who would come to the rescue and provide a humble, but correct answer to our question? Our steward!

We were hungry (even doing nothing aboard a ship on high seas makes you hungry – and this was not a cruise ship, but a freighter that accepted up to ten adventurous passengers). The chicken salad on toast looked delicious. Our East Asia part of the “Round-the-World” trip was nearing its end. “A relaxing experience for body and soul on a genuine freighter” the travel brochure had said. Another 11 days and we’d be home. It was Sunday; Mauritius and the Cape of Good Hope lay behind us; we were in the South Atlantic Ocean. I grabbed the silver fork and was about to poke it into that mouth-watering, appetizingly garnished salad, when my eyes noticed a multi-legged, brown something, struggling to free itself from the yellowish mayonnaise it was hopelessly stuck in. A live cockroach!

Lying on its back, it was caught in sticky, creamy substrate. Without telling my husband or alarming the other passengers, who were happily chatting and munching away, I succeeded in getting rid of the vermin and shoved it under the table. I tried to step on the menace and felt the crunch of its resistive cuticle through my bones, when my foot finally got hold of it. Never in my life have I killed a bug with such disgust and delight at the same time. I shuddered; it was over.

Now, I do well know that cockroaches, members of the ancient insect family known as Blattids, do not harm anyone. And I drew some comfort from the thought that these insects are not known to transmit diseases like, for instance, flies do, that they don’t sting like wasps, and that they don’t suck blood like mosquitoes. I had also been told earlier by my husband that most ships were said to have them and that even hospitals, chocolate factories and bakeries were usually not free of them. And yet – this ugly beast on my plate, in my mayonnaise, waving its thin and hairy legs at me, that was too much. I had thoroughly lost my appetite.

Manly and erect our handsome young steward rushed by to see if he could remove empty plates and unwanted dishes. Always attentive he noticed my lack of appetite and compassionately put it down to the stormy conditions outside and the rolling of our vessel. Perhaps there was a slight tone of mockery or mischievousness in his voice. Of course, even the best steward can overlook something, especially when it is a small, brown beetle-like insect covered in mayonnaise.

Nonetheless, from now on I became somewhat more critical and looked at our steward a little more carefully. Between meal times I was evaluating my observations. Curious – I was thinking had he perhaps got sloppier the closer the end of the trip drew near? He, who had always been so immaculately dressed and so well-groomed, wasn’t he often uncombed now when he served breakfast? His slender fingers, when they handed out the cutlery, did I not detect a touch of uncleanliness on them? And didn’t his fingernails look bitten and sometimes even outright dirty? I was supposed to look at the label, but couldn’t help focusing on the hand instead that held the bottle of “Riesling” when my glass was filled and I now thought I had found the answer, why our steward kept hiding his left hand behind his back when filling our glasses.

True, a hard-working steward, the powerful soapy water full of detergents, his daily dish washing and glass cleaning routines, that’s tough on one’s manicure and skin care. But his white shirts – it really seemed to me that he no longer was changing them every day and a stench of sweat seemed to be emitted from them when he passed by. And his beard: did he actually ever trim it? Did he even care? I wondered whether he brushed his teeth regularly.

I began to think I could smell his presence even if I did not see him. His witty remarks, his informative talk, nothing much behind it, I concluded. Mostly rehearsed platitudes, told a hundred times; shallow and stupid phrases made at the wrong time. Who knows, perhaps he even smoked secretly, drank in his cabin, took drugs. It was all possible.

The Bay of Biscay, another two or three days. By now I was convinced that I had never seen a more vulgar, filthy and uncaring person than this man, who called himself “Salon Steward”. Subconsciously, I worried whether I was perhaps doing him injustice and he wasn’t so bad after all. But then again, why was he so unpleasant, so irritating since he had placed the salad with the cockroach in front of me?

I decided I would not meet him any more and begged my husband to bring my food up to our cabin for the last two days. However, there on my own, I ate even less. I became weak and ill and in the British Channel thought I had to die. We reached Southampton just in time. One more day and I would surely not have made it alive.

Thus ended our once-in-a-lifetime 2 ½ month East Asia leg of the “Round-the-World” trip: a “relaxing experience for body and soul” – just like the travel brochure had promised.

© Dr V.B. Meyer-Rochow and, 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 with appropriate and specific direction to the original content.