In the latest display in our Presenting… series, collections manager Amoret Spooner takes a look at the wonderful and sometimes strange world of the praying mantis.
Praying mantis is the common name given to an order of insects called Mantodea, a word which derives from mantis meaning prophet, and eidos meaning form or type. The more familiar ‘praying mantis’ refers to the striking way that they hold their large forelimbs, in a ‘praying’ posture.
There are over 2,400 species of mantis worldwide, split into 21 different families. The image above shows their incredible diversity of colour, shape and size. But while they may differ in appearance, their biology and many behavioural traits are the same.
Mantis are predators of insects, including other mantis, but larger species will eat small lizards and birds. But they are perhaps best known for being cannibalistic. This behaviour is most commonly seen in nymphs straight out of the egg case, or ootheca, but it can also occur when the female eats the male after mating. However, cannibalism is not required to mate, so when it happens it’s usually because the female is hungry!
The egg case, or ootheca, of mantis vary greatly depending on the size and behaviour of the species.Revisio Insectorum Familiae Mantidarum was one of John Obadiah Westwood’s greatest works. Thankfully he kept all of his drawings, annotated pages and notes for the publication, allowing us an insight into the years of work he put into its production.
Praying mantis are ambush hunters, either camouflaging themselves while waiting for their prey to approach, or actively stalking prey. Their compound eyes are specialised in perceiving motion, and are widely spaced giving them a wide field of vision. Along with powerful front legs and an ability to move the head up to 180°, this makes them successful predators.
The Museum’s archive contains original drawings and annotations by John Obadiah Westwood (1805–1893), the first Hope Professor of Zoology. As a renowned scientist Westwood described many new mantis species, and he was also a talented artist.
The Presenting… Marvellous Mantodea case is on display at the Museum until 1 November 2018.
This article is taken from European research magazine Horizon as part of our partnership to share natural environment science stories with readers of More than a Dodo. For more on the development of the brain see our Brain Diaries exhibition site.
One of the major features that distinguishes humans from other primates is the size of our brains, which underwent rapid evolution from about two to three million years ago in a group of our ancestors in Africa called the Australopithecines. During this period, the human brain grew almost three-fold to reach its current size. Scientists know this from skull remains, but have puzzled over how it happened…
This year, the mystery was partially solved by Professor Pierre Vanderhaeghen at the Flanders Institute for Biotechnology in Belgium. Prof. Vanderhaeghen, who was conducting his work as part of the GENDEVOCORTEX project, went on a hunt for the genes that drove the growth of human brains.
Scientists had suspected that brain expansion began in our human ancestors when they evolved genes that are switched on in the foetus, when a lot of key brain development occurs. Prof. Vanderhaeghen therefore looked for genes present in human foetal tissue, but missing from our closest living relatives, apes.
His lab discovered 35 hominid – present only in apes and humans – genes that were active in foetal brain tissue. They then became intrigued by three specific genes – all similar to NOTCH genes, an ancient gene family involved in sending messages between cells and that are present in all animals. They found that the three new genes, collectively named NOTCH 2NL, were created by a “copy and paste error” of an original NOTCH gene.
This error created entirely new proteins which likely helped our ancestors’ cerebral cortex to balloon. This is the part of our brain responsible for our language, imagination and problem-solving abilities. Scientists at the University of California, Santa Cruz, have also identified the NOTCH 2NL genes in DNA from Homo sapiens’ extinct cousins – the Neanderthals and Denisovans.
(The NOTCH 2NL) genes are only present in humans today. They were also present in Neanderthal DNA, but not in chimpanzees
Prof. Vanderhaeghen
Evolution These genes control the growth rate and differentiation of brain stem cells – the starter cells that multiply and give rise to all neurons in our brain – causing them to seed more nerve cells, which in turn helped to expand brain size. The genes likely led to more neurons and brain tissue in our ancestor’s descendants – including Neanderthals, Denisovans, and modern humans.
Prof. Vanderhaeghen’s research could also help to provide new insights into brain disorders. The US researchers linked genetic faults in DNA that were very similar to NOTCH 2NL, to children born with enlarged brains or small brains. Many of the new human-specific genes are located in a small area of our genome that plays an important role in brain size, according to Prof. Vanderhaeghen.
As DNA in this area closely resembles another part of the genome where it was originally cut and pasted from millions of years ago, errors are more likely, said Prof. Vanderhaeghen. “Patients who have (inherited) deletions in this area tend to be at risk of developing schizophrenia, whereas patients with duplications are more at risk of autistic spectrum disorder,” he said.
Prof. Vanderhaeghen is now studying some 20 of the remaining human-only genes to see how they contributed to the evolution of the human brain.
Something like 40-50% of the Neanderthal genome can still be found in people today.
Prof. Svante Pääbo, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
The use of genetics to study human evolution in this way is helping to transform our understanding of how our own species compared to our ancestors. Traditionally, scientists have studied extinct species by looking at the fossilised remains of their bones. This was how they discovered the existence of Neanderthals, the extinct human species that lived across Europe and much of Asia before vanishing around 40,000 years ago.
In the last decade, however, scientists have begun to look at the DNA inside these bones. Professor Svante Pääbo, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has led the way in sequencing DNA of these extinct humans from small bone fragments.
This allows scientists to compare modern human DNA with that of extinct humans, rather than just living relatives like chimps. Already, the work has revealed some surprising findings – our own species appears to have interbred with some of these ancient relatives during our history.
Ancient humans Scientists have found that the DNA of every person outside Africa is 1-2% Neanderthal, meaning that these extinct human relatives had offspring with our own ancestors.
An international consortium of researchers is sequencing the 3 billion bases that make up the genome of our closest relative – the Neanderthal. The sequence is generated from DNA extracted from three Croatian Neanderthal fossils using novel methods developed for this project. Image credit – Frank Vinken for Max Planck Society
“Different people tend to carry different pieces of the Neanderthal genome,” said Prof. Pääbo, who is undertaking a project called 100 Archaic Genomes to decipher the DNA of ancient human individuals. “Something like 40-50% of the Neanderthal genome can still be found in people today,” he said.
According to Prof. Pääbo, we retained some of this DNA because it offered an advantage to our ancestors. “Some (of this retained DNA) has to do with the immune system, presumably helping us to fight off infectious diseases.”
The power of genetics to unravel the history of human evolution took a new twist in 2010 after Prof. Pääbo’s lab sequenced DNA from a finger bone fragment found by a Russian archaeological team in a remote Siberian cave.
The analysis revealed the bone belonged to a previously unknown human relative, now called Denisovans after Denisova Cave where the bone was found. This mysterious ancient human species lived at around the same time as Neanderthals, but further east into Asia.
Last year, Prof. Pääbo’s group published DNA sequences from a tooth found in the cave – the fourth ever Denisovan discovered. We now know Denisovan DNA carries more variation than Neanderthal DNA, leading scientists to conclude that they were more widespread than the better-known Neanderthals.
Denisovans left a more impressive stamp on some of us than Neanderthals, according to Prof Pääbo. Their DNA can be found in people across Asia today, while indigenous peoples of Papua New Guinea and Australia may carry up to 5%. Tibetans also carry some Denisovan DNA in their genomes, which has helped them adapt to life at high altitudes where there is little oxygen in the atmosphere.
Prof. Pääbo and his colleagues will soon publish their third high-quality genome – where almost the entire DNA sequence is intact – of a Neanderthal from Siberia. A deciphered genome of this quality allows for better DNA comparisons and could tell us more about the evolution of important genes – such as those linked to the development and function of the brain. It will add yet another puzzle piece to help us understand the history of our closest extinct relatives, according to Prof. Pääbo.
“There may even be other forms of extinct humans out there to be discovered by studying the DNA of the (ancient) bones we find,” he said.
Top image: The skull of a Australopithecus sediba, a species of Australopithecines, who were our ancestors and whose brains started to grow two to three million years ago. Image credit – Australopithecus sediba by Brett Eloff, courtesy Profberger and Wits University is licensed under CC BY-SA 4.0.
Cephalopods are a remarkable group of molluscs that includes nautilus, octopuses, cuttlefish and various groups of ‘squid’. The other major groups of molluscs includes more familiar shelled animals such as gastropods (snails and slugs), bivalves, and chitons, as well as some less familiar forms.
In natural history museums, molluscs are normally represented by shell collections because the hard shelly parts are easier to preserve and store than the soft tissue. This creates a bias against the soft-bodied cephalopods, such as squids, octopuses and cuttlefish, because aside from the cuttlebones of cuttlefish and the thin gladius in squids there aren’t many hard parts that can be preserved to represent these animals in dry collections. For octopuses it’s normally only the beak and microscopic radulae, a toothed tongue-like structure, that can be preserved. But there is one notable exception: the eggcases of argonauts.
Model of Argonauta argo. Image: Mark Carnall
Argonauts, four* species of octopuses in the genus Argonauta, are unusual in that they produce a paper-thin eggcase, sometimes referred to as a shell. Unlike a true shell it’s not attached to the body of the argonaut, but secreted by two specialised webbed arms. The eggcases themselves are sometimes called paper nautiluses because they resemble the spiral shells of nautiluses, but they are structurally and functionally very different.
External morphology of a female paper nautilus (Argonauta argo) with eggcase. Poli, Giuseppe Saverio. Testacea utriusque Siciliae. (1791-1827). http://biodiversitylibrary.org/page/44020354
Argonaut eggcases wash on up shorelines around the world and have been known for centuries. But it’s only comparatively recently that the origin and use of these cases has been described. When eggcases containing live argonauts were first encountered it was supposed that argonauts were reusing empty shells created by another animal, much like hermit crabs repurpose gastropod shells.
Pioneering research by marine biologist Jeaneatte Villepreux-Power in the 19th century led to observations of Octopus and Argonauta, confirming that the eggcases are made and repaired by female argonauts. It wasn’t until 2010 that we understood how argonauts use these cases to float in the ocean. It turns out that they ‘bob’ their shells to gulp a pocket of air. Then, using their second pair of arms, they trap the air in the top of the shell and dive releasing enough air to maintain the required buoyancy.
Only female argonauts make the eggcases, so the free-floating males are tiny in comparison. In addition to providing a home for female argonauts, these structures are used to brood embryos in. One eggcase was described with nearly 50,000 embryos attached to the inside of the shell.
Preparation showing series of argonaut egg cases of varying sizes.
Thanks to their oddity and beauty these eggcases are common in museum collections, but they represent one of the marvels of evolution. Unlike many bottom-dwelling octopuses, female argonauts have evolved this amazing structure to function as an underwater craft to allow them to leave the ocean floor and inhabit the open oceans: the true astronauts of the sea.
To celebrate the pioneering work of Jeaneatte Villepreux-Power, these amazing animals, their eggcases, and a selection of museum specimens are on display in the Museum’s Presenting… case until the 3 July 2018.
As one of the many scientists who contributed to our Settlers exhibition, geneticist Dr Calliope Dendrou from the Wellcome Centre for Human Genetics ran a Spotlight talk as part of the exhibition’s event programme, where she explained more about her research into genetics and autoimmune diseases…
Our genes make us who we are – they are what unite us a single species, Homo sapiens – but they are also what make us unique individuals, with a particular set of characteristics. Genes are made up of DNA inherited from one individual to the next, transmitting the code for life through time.
The DNA ‘alphabet’ comprises four letters, A, C, G and T, and three billion of these letters make up the complete human genome. Comparing two unrelated individuals, on average around one in 1,000 of the three billion letters will differ. Genetically speaking, each of us is 99.9 percent the same as every other unrelated person.
Studying our genetic composition and the similarities and differences between individuals is of interest from a historical, geographic and sociological perspective, as the Settlers exhibition at the Museum shows. But it can also have medical implications for our understanding of the types of diseases we are susceptible to.
Immune cell (yellow) engulfing anthrax bacteria (orange). Image: Volker Brinkmann [CC BY 2.5], via Wikimedia CommonsMy lab works on the genetics of autoimmune diseases, which affect some ten percent of people worldwide and include relatively common conditions such as rheumatoid arthritis, multiple sclerosis, and type 1 diabetes.
Autoimmune diseases arise when the cells of the immune system function inappropriately. The immune system is made up of millions of immune cells patrolling the body, sensing their environment and sending signals to each other.
If the body has been injured due to physical trauma or an infection, then upon receiving the right signals immune cells help to clear damaged cells or fight off pathogens. But sometimes immune cells can begin to respond to the wrong signals, triggering a self-destruction. When this happens they can destroy the body’s own tissues and organs and then autoimmune start to diseases develop.
The common autoimmune diseases are very complex and are thought to result from a combination of genetic and environmental influences. Hundreds of genetic factors can influence someone’s risk of autoimmune disease development, so having a low or high risk is a genetic lottery – it depends on how many different genetic factors happened to have come together for that person.
We are investigating the biological consequences of these genetic factors to find better ways to target the immune cells that are attacking the body. The trick is to do this without suppressing the immune system’s ability to fight off infection, a problem associated with drugs used treat autoimmune disease patients today.
A phylogeny? An evolutionary tree? A cladogram? We see the branching lines of these diagrams in many museum displays and science articles, but what do they tell us and why are they helpful?
Actually, no, there’s no such thing as a fish. Let’s take a step back…
The Jackson 5 – the ultimate singing family tree? Credit: Wikimedia Commons
It all comes down to common ancestry. All life is related, and we can think of it in terms of a family tree (or ‘phylogeny’): Jackie, Tito, Jermaine, Marlon and Michael were all Jacksons. United not only by a collective inability to control their feet, but also by common descent – they are all their parent’s children*.
By tracing further and further back in MJs family tree we could define ever larger groups united by common ancestors, first cousins (grandparents), second cousins (great-grandparents), all the way to every human, every mammal, every animal, and eventually all life – we are family (ok, that was Sister Sledge, but you get the point).
In the case of the tree of life, species are at the tips of branches and their common ancestors are where branches meet. A true biological group consists of a common ancestor and all its descendants, and we can use characteristics common between two species to imply common descent. Siblings look a lot like each other because they have inherited much of their appearance via common ancestry (i.e. their parents). In a similar way, two closely related species will share lots of inherited characteristics.
However, things are not quite that simple. Wings of bats, birds and insects are not inherited from a common ancestor but independently evolved for the same purpose, in this case flight. To complicate things further, as species evolve they may lose features inherited from their ancestors that other descendants retain. Snakes have lost their limbs, but still sit in the same group as lizards. These problems can be overcome by looking at many characteristics at once, using genetic information to test predicted relationships, and adding fossils to the tree to track change or loss through time (as in snakes).
Birds, insects and bats have all evolved wings for flight, but did not inherit this feature from a common ancestor. This is a good example of convergent evolution.
So, what about fish? ‘Fish’ is used to refer to pretty much anything that swims in water, but this lifestyle in animals like starfish (a relative of crinoids and sea urchins), jellyfish (a relative of corals) and cuttlefish (a relative of squid and octopus) evolved independently from more familiar fish like cod and carp. So, they’re not really ‘fish’ at all. With that in mind, how can we be fish? Well, the last common ancestor of, say, hagfish, salmon, shark and lungfish, is also the common ancestor of frogs, lizards, cats and us! All four-limbed animals with backbones descend from a fish-like ancestor. To complicate things further some have adapted to life back into the water and look much more like a ‘fish’ again, like dolphins, seals and the extinct ichthyosaur. Without a tree of life, we could not begin to unravel the evolutionary path that lead to all the diversity of life we see today.
The Blue Fin Tuna on display in the Museum is definitely a fish… right?!
You are closer to a chimp than a monkey, closer to a starfish than a snail, and closer to a mushroom than a tree. And, of course, there’s no such thing as a fish, but they still go well with chips.
*Joseph Jackson and Katherine Scruse had ten children, including the members of the Jackson 5, twenty-six grandchildren and several great-grandchildren.
Our Settlers exhibition tells the story of the peopling of Britain, from the arrival of the earliest modern humans over 40,000 years ago to the population of the present day. At the centre of the exhibition is a genetic map of Britain – the first of its kind to be produced of anywhere in the world. But what exactly does this map show us and how was it created? Brian Mackenwells from the Wellcome Centre for Human Genetics explains…
While maps can be used to show us where we need to go, the one at the heart of the People of the British Isles study was used to show us where we’ve been. Researchers from the Wellcome Centre for Human Genetics wanted to reach back through time by looking at our genetic code.
We obviously can’t travel back a hundred years and sequence people’s DNA, so the next best thing is to sequence the genome of people whose grandparents were all from the same rural area. This is because people in rural areas at that time had a tendency not to travel very far, so the researchers guessed that the genes of their descendants would be like (slightly jumbled) snapshots of the genetic history of the area they were from.
This video, commissioned from Oxford Sparks especially for the exhibition, expands on this idea.
So the People of the British Isles researchers sequenced the DNA of just over 2,000 people and set to work analysing it all. The scientists looked for individuals with common genetic patterns and grouped them together. They had no idea where the individuals were actually from; the system just grouped people whose small genetic variations seemed to be the most similar to each other.
Here’s an example of the process. Imagine you were presented with a list of colours like these and asked to group them.
You would probably group them something like this:
There would be a ‘sort of red’ group, a ‘sort of green’ group, and a ‘sort of blue’ group. This is what the pattern-matching system was trying to do with genetic codes: make clusters of people who seemed to be similar to each other based on very small genetic variations.
But the really surprising bit came next. We took each individual in the study and plotted them on a map of Britain based on the location of their grandparents, using a symbol to denote which genetic cluster they had been placed in.
We weren’t sure what to expect. Would the symbols be spread out randomly over the map, or would there be groupings? What might the groupings mean?
The result was striking: the genetic clusters are, for the most part, linked to quite specific geographical areas, as you can see in the final map here.
The People of the British Isles genetic map of Britain was the first map of its kind of anywhere in the world. Each marker represents a participant in the study, and the different symbols represented different genetic clusters. It’s clear that the genetic clusters are connected with geography.
What is this map revealing to us? When we compared these different groups to the unique genetic markers of different European populations, working with archaeologists and geographers, we were able to start to understand the meaning of the map. You can clearly see the genetic footprints left by historical migration and events from hundreds of years ago. The video below explains more about this.
The locations of many of the clusters correspond to regions controlled by known historical tribes and kingdoms. The map also shows how places like Northern Ireland and Western Scotland seem to share a genetic heritage.
You can learn more about the map, and the things we’ve learned from it, at the Settlers exhibition until the 16 September 2018.
A phylogeny? An evolutionary tree? A cladogram? We see the branching lines of these diagrams in many museum displays and science articles, but what do they tell us and why are they helpful?
