The caterpillar did something extraordinary – it mimicked a small snake
Have you ever seen an elephant hawk moth? If you live in Europe or Asia you might have spotted one of these amazing insects. In the United Kingdom they are fairly common, but perhaps not often seen. It’s a real treat to spot an adult or a caterpillar, both are amazing sights.
Walking in the Cotswold Water Park recently, near the Gateway Centre on Lake 6, we spotted an elephant hawk moth caterpiller crossing the footpath (close to the grey circle in the map.
For a short time we just watched as it made its way across the path. But before it made it to the vegetation on the far side, some people appeared with a dog. The dog ran up enthusiastically to greet us and accidentally kicked the caterpiller before running off again. The caterpillar did something extraordinary – it mimicked a small snake.
Am I a caterpillar, or am I a snake?
For perhaps 20 seconds or so it writhed its body in a convincingly snakelike movement, and it pumped up several body segments behind the head, tucking its head down at the same time. With eye spot markings on its flanks, a scaly pattern on the entire body, and by raising up the front part of the body, it really did look the part. I wasn’t fast enough to get a photo, but I did get some video of the recovered caterpillar continuing on its way afterwards.
Searching the internet later, I found several good images of the caterpillar mimicking a small snake. Perhaps the best of these is show below.
The natural world is so amazing, and so full of surprises, but mimicry is quite a common feature in both plants and animals. The European white dead-nettle has leaves that cannot sting but match the appearance of the unrelated stinging nettle very closely. Some insects look like pieces of wood, or a leaf, or a patch of white lichen, or a bird dropping. Many slugs look very much like animal droppings of various kinds, and as they move so slowly only an alert predator is likely to notice them. Predators, too, use camouflage which is not truly mimicry, but helps them merge into dappled sunshine and shade. Fish are often dark on top and silvery underneath. Sometimes they are patterned and look like the gravel bed of a stream or river.
Way back a thousand million years ago when the super-continent Rodinia existed
Well, OK, it’s not that the canyon itself is partly in Australia, but the rock formations through which the canyon was formed are partly in Australia.
How do we know? Many of those rock layers with their very distinctive and unique sequences and chemical compositions have also now been found in Tasmania, the large island just south of the Australian state of New South Wales. It’s the oldest rocks of the Grand Canyon series that have been discovered in Tasmania. The rocks have always seemed unrelated to other rocks in the same part of the island, but they look like the oldest canyon rocks in many of their details and make-up.
The solution to this puzzle can only be that part of Australia was once a single piece of continental crust with the rocks of the Grand Canyon. That would have been way back a thousand million years ago when the super-continent Rodinia existed. Since then, the continents have broken apart, moved around, run into one another, and broken apart again. The breakup of Rodinia separated the early rock grouping into pieces that became part of modern North America and Australia.
This is not a new theme in the history of the continents. In a much more recent episode (the opening of the Atlantic Ocean) an ancient mountain chain was torn in two; the parts now form the Appalachians in North America and the Scottish Highlands on the edge of Europe.
But this new discovery helps scientists put more detail into the very early story of continental crustal movement and break up. Thanks to Jack Mulder and others for publishing the discovery and New Scientist for sharing the story more widely.
Imagine an RNA molecule that can replicate … this is already quite life-like.
I have a really exciting story for you today, especially if you are interested in the origin of life and evolution.
A recent article in the magazine Science reports that Thomas Carell, a chemist at Ludwig Maximilian University in Munich, Germany, has outlined a process that can generate all four of the building blocks of RNA from compounds and conditions present on the pre-biotic Earth.
Why is this significant?
To understand, we need to grasp the importance of RNA. Its cousin, DNA, is the molecule used by most living things on Earth to store the genetic information that controls their form and function. RNA is also capable of storing genetic information, and some viruses use it in exactly this way. RNA is also essential in all living forms because it acts as a go between in the production of proteins from the DNA genetic material. RNA is less stable than DNA and copying errors are more likely. For this reason, DNA is a better long-term genetic store than RNA, but RNA is more dynamic. Think in terms of DNA as a library of printed recipe books, while RNA is like hand-copied notes on scraps of paper that enable the recipes to be taken to the kitchen.
But RNA has additional tricks up its sleeve. Not only can this molecule store genetic information, it can also catalyse biochemical reactions, including the synthesis of simple proteins. RNA is a bit of an all-rounder, and it’s not so hard to imagine that quite soon after being randomly synthesised by Carell’s process, RNA molecules might be formed as the dissolved RNA bases came into contact with tiny rock templates that could act to stabilise the process.
RNA also has the potential to self-replicate. Imagine an RNA molecule that can replicate (albeit with occasional errors). This is already quite life-like. Now image the population growing in places where the Carell process was providing reliable supplies of the four bases. Some of those RNA molecules will have errors, sooner or later an error, or a combination of errors will provide a version that replicates more efficiently, or gets trapped inside a lipid membrane that protects it from breakdown, or catalyses the production of a protein that makes the RNA more efficient in some way. If all of those things happen you have something that might be regarded as an early living form – an enclosed lipid membrane with a self-replicating genetic system that can mutate and evolve. Nothing more than that would be needed to kick of an expanding array of related forms.
The story as I describe it here is not complete and likely incorrect in many ways. I accept that. But though it’s a simplistic view, it’s also likely to be broadly correct as a bare outline. Over the next few years and decades I expect much more detail will become clear, especially detail about what is or is not possible. And I expect to see many of the steps to be experimentally demonstrated. Watch this space…